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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * kernel/lockdep.c
- *
- * Runtime locking correctness validator
- *
- * Started by Ingo Molnar:
- *
- * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <[email protected]>
- * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
- *
- * this code maps all the lock dependencies as they occur in a live kernel
- * and will warn about the following classes of locking bugs:
- *
- * - lock inversion scenarios
- * - circular lock dependencies
- * - hardirq/softirq safe/unsafe locking bugs
- *
- * Bugs are reported even if the current locking scenario does not cause
- * any deadlock at this point.
- *
- * I.e. if anytime in the past two locks were taken in a different order,
- * even if it happened for another task, even if those were different
- * locks (but of the same class as this lock), this code will detect it.
- *
- * Thanks to Arjan van de Ven for coming up with the initial idea of
- * mapping lock dependencies runtime.
- */
- #define DISABLE_BRANCH_PROFILING
- #include <linux/mutex.h>
- #include <linux/sched.h>
- #include <linux/sched/clock.h>
- #include <linux/sched/task.h>
- #include <linux/sched/mm.h>
- #include <linux/delay.h>
- #include <linux/module.h>
- #include <linux/proc_fs.h>
- #include <linux/seq_file.h>
- #include <linux/spinlock.h>
- #include <linux/kallsyms.h>
- #include <linux/interrupt.h>
- #include <linux/stacktrace.h>
- #include <linux/debug_locks.h>
- #include <linux/irqflags.h>
- #include <linux/utsname.h>
- #include <linux/hash.h>
- #include <linux/ftrace.h>
- #include <linux/stringify.h>
- #include <linux/bitmap.h>
- #include <linux/bitops.h>
- #include <linux/gfp.h>
- #include <linux/random.h>
- #include <linux/jhash.h>
- #include <linux/nmi.h>
- #include <linux/rcupdate.h>
- #include <linux/kprobes.h>
- #include <linux/lockdep.h>
- #include <linux/context_tracking.h>
- #include <asm/sections.h>
- #include "lockdep_internals.h"
- #include <trace/events/lock.h>
- #ifdef CONFIG_PROVE_LOCKING
- static int prove_locking = 1;
- module_param(prove_locking, int, 0644);
- #else
- #define prove_locking 0
- #endif
- #ifdef CONFIG_LOCK_STAT
- static int lock_stat = 1;
- module_param(lock_stat, int, 0644);
- #else
- #define lock_stat 0
- #endif
- #ifdef CONFIG_SYSCTL
- static struct ctl_table kern_lockdep_table[] = {
- #ifdef CONFIG_PROVE_LOCKING
- {
- .procname = "prove_locking",
- .data = &prove_locking,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = proc_dointvec,
- },
- #endif /* CONFIG_PROVE_LOCKING */
- #ifdef CONFIG_LOCK_STAT
- {
- .procname = "lock_stat",
- .data = &lock_stat,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = proc_dointvec,
- },
- #endif /* CONFIG_LOCK_STAT */
- { }
- };
- static __init int kernel_lockdep_sysctls_init(void)
- {
- register_sysctl_init("kernel", kern_lockdep_table);
- return 0;
- }
- late_initcall(kernel_lockdep_sysctls_init);
- #endif /* CONFIG_SYSCTL */
- DEFINE_PER_CPU(unsigned int, lockdep_recursion);
- EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
- static __always_inline bool lockdep_enabled(void)
- {
- if (!debug_locks)
- return false;
- if (this_cpu_read(lockdep_recursion))
- return false;
- if (current->lockdep_recursion)
- return false;
- return true;
- }
- /*
- * lockdep_lock: protects the lockdep graph, the hashes and the
- * class/list/hash allocators.
- *
- * This is one of the rare exceptions where it's justified
- * to use a raw spinlock - we really dont want the spinlock
- * code to recurse back into the lockdep code...
- */
- static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
- static struct task_struct *__owner;
- static inline void lockdep_lock(void)
- {
- DEBUG_LOCKS_WARN_ON(!irqs_disabled());
- __this_cpu_inc(lockdep_recursion);
- arch_spin_lock(&__lock);
- __owner = current;
- }
- static inline void lockdep_unlock(void)
- {
- DEBUG_LOCKS_WARN_ON(!irqs_disabled());
- if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
- return;
- __owner = NULL;
- arch_spin_unlock(&__lock);
- __this_cpu_dec(lockdep_recursion);
- }
- static inline bool lockdep_assert_locked(void)
- {
- return DEBUG_LOCKS_WARN_ON(__owner != current);
- }
- static struct task_struct *lockdep_selftest_task_struct;
- static int graph_lock(void)
- {
- lockdep_lock();
- /*
- * Make sure that if another CPU detected a bug while
- * walking the graph we dont change it (while the other
- * CPU is busy printing out stuff with the graph lock
- * dropped already)
- */
- if (!debug_locks) {
- lockdep_unlock();
- return 0;
- }
- return 1;
- }
- static inline void graph_unlock(void)
- {
- lockdep_unlock();
- }
- /*
- * Turn lock debugging off and return with 0 if it was off already,
- * and also release the graph lock:
- */
- static inline int debug_locks_off_graph_unlock(void)
- {
- int ret = debug_locks_off();
- lockdep_unlock();
- return ret;
- }
- unsigned long nr_list_entries;
- static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
- static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
- /*
- * All data structures here are protected by the global debug_lock.
- *
- * nr_lock_classes is the number of elements of lock_classes[] that is
- * in use.
- */
- #define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
- #define KEYHASH_SIZE (1UL << KEYHASH_BITS)
- static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
- unsigned long nr_lock_classes;
- unsigned long nr_zapped_classes;
- unsigned long max_lock_class_idx;
- struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
- DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
- static inline struct lock_class *hlock_class(struct held_lock *hlock)
- {
- unsigned int class_idx = hlock->class_idx;
- /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
- barrier();
- if (!test_bit(class_idx, lock_classes_in_use)) {
- /*
- * Someone passed in garbage, we give up.
- */
- DEBUG_LOCKS_WARN_ON(1);
- return NULL;
- }
- /*
- * At this point, if the passed hlock->class_idx is still garbage,
- * we just have to live with it
- */
- return lock_classes + class_idx;
- }
- #ifdef CONFIG_LOCK_STAT
- static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
- static inline u64 lockstat_clock(void)
- {
- return local_clock();
- }
- static int lock_point(unsigned long points[], unsigned long ip)
- {
- int i;
- for (i = 0; i < LOCKSTAT_POINTS; i++) {
- if (points[i] == 0) {
- points[i] = ip;
- break;
- }
- if (points[i] == ip)
- break;
- }
- return i;
- }
- static void lock_time_inc(struct lock_time *lt, u64 time)
- {
- if (time > lt->max)
- lt->max = time;
- if (time < lt->min || !lt->nr)
- lt->min = time;
- lt->total += time;
- lt->nr++;
- }
- static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
- {
- if (!src->nr)
- return;
- if (src->max > dst->max)
- dst->max = src->max;
- if (src->min < dst->min || !dst->nr)
- dst->min = src->min;
- dst->total += src->total;
- dst->nr += src->nr;
- }
- struct lock_class_stats lock_stats(struct lock_class *class)
- {
- struct lock_class_stats stats;
- int cpu, i;
- memset(&stats, 0, sizeof(struct lock_class_stats));
- for_each_possible_cpu(cpu) {
- struct lock_class_stats *pcs =
- &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
- for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
- stats.contention_point[i] += pcs->contention_point[i];
- for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
- stats.contending_point[i] += pcs->contending_point[i];
- lock_time_add(&pcs->read_waittime, &stats.read_waittime);
- lock_time_add(&pcs->write_waittime, &stats.write_waittime);
- lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
- lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
- for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
- stats.bounces[i] += pcs->bounces[i];
- }
- return stats;
- }
- void clear_lock_stats(struct lock_class *class)
- {
- int cpu;
- for_each_possible_cpu(cpu) {
- struct lock_class_stats *cpu_stats =
- &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
- memset(cpu_stats, 0, sizeof(struct lock_class_stats));
- }
- memset(class->contention_point, 0, sizeof(class->contention_point));
- memset(class->contending_point, 0, sizeof(class->contending_point));
- }
- static struct lock_class_stats *get_lock_stats(struct lock_class *class)
- {
- return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
- }
- static void lock_release_holdtime(struct held_lock *hlock)
- {
- struct lock_class_stats *stats;
- u64 holdtime;
- if (!lock_stat)
- return;
- holdtime = lockstat_clock() - hlock->holdtime_stamp;
- stats = get_lock_stats(hlock_class(hlock));
- if (hlock->read)
- lock_time_inc(&stats->read_holdtime, holdtime);
- else
- lock_time_inc(&stats->write_holdtime, holdtime);
- }
- #else
- static inline void lock_release_holdtime(struct held_lock *hlock)
- {
- }
- #endif
- /*
- * We keep a global list of all lock classes. The list is only accessed with
- * the lockdep spinlock lock held. free_lock_classes is a list with free
- * elements. These elements are linked together by the lock_entry member in
- * struct lock_class.
- */
- static LIST_HEAD(all_lock_classes);
- static LIST_HEAD(free_lock_classes);
- /**
- * struct pending_free - information about data structures about to be freed
- * @zapped: Head of a list with struct lock_class elements.
- * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
- * are about to be freed.
- */
- struct pending_free {
- struct list_head zapped;
- DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
- };
- /**
- * struct delayed_free - data structures used for delayed freeing
- *
- * A data structure for delayed freeing of data structures that may be
- * accessed by RCU readers at the time these were freed.
- *
- * @rcu_head: Used to schedule an RCU callback for freeing data structures.
- * @index: Index of @pf to which freed data structures are added.
- * @scheduled: Whether or not an RCU callback has been scheduled.
- * @pf: Array with information about data structures about to be freed.
- */
- static struct delayed_free {
- struct rcu_head rcu_head;
- int index;
- int scheduled;
- struct pending_free pf[2];
- } delayed_free;
- /*
- * The lockdep classes are in a hash-table as well, for fast lookup:
- */
- #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
- #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
- #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
- #define classhashentry(key) (classhash_table + __classhashfn((key)))
- static struct hlist_head classhash_table[CLASSHASH_SIZE];
- /*
- * We put the lock dependency chains into a hash-table as well, to cache
- * their existence:
- */
- #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
- #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
- #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
- #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
- static struct hlist_head chainhash_table[CHAINHASH_SIZE];
- /*
- * the id of held_lock
- */
- static inline u16 hlock_id(struct held_lock *hlock)
- {
- BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
- return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
- }
- static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
- {
- return hlock_id & (MAX_LOCKDEP_KEYS - 1);
- }
- /*
- * The hash key of the lock dependency chains is a hash itself too:
- * it's a hash of all locks taken up to that lock, including that lock.
- * It's a 64-bit hash, because it's important for the keys to be
- * unique.
- */
- static inline u64 iterate_chain_key(u64 key, u32 idx)
- {
- u32 k0 = key, k1 = key >> 32;
- __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
- return k0 | (u64)k1 << 32;
- }
- void lockdep_init_task(struct task_struct *task)
- {
- task->lockdep_depth = 0; /* no locks held yet */
- task->curr_chain_key = INITIAL_CHAIN_KEY;
- task->lockdep_recursion = 0;
- }
- static __always_inline void lockdep_recursion_inc(void)
- {
- __this_cpu_inc(lockdep_recursion);
- }
- static __always_inline void lockdep_recursion_finish(void)
- {
- if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
- __this_cpu_write(lockdep_recursion, 0);
- }
- void lockdep_set_selftest_task(struct task_struct *task)
- {
- lockdep_selftest_task_struct = task;
- }
- /*
- * Debugging switches:
- */
- #define VERBOSE 0
- #define VERY_VERBOSE 0
- #if VERBOSE
- # define HARDIRQ_VERBOSE 1
- # define SOFTIRQ_VERBOSE 1
- #else
- # define HARDIRQ_VERBOSE 0
- # define SOFTIRQ_VERBOSE 0
- #endif
- #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
- /*
- * Quick filtering for interesting events:
- */
- static int class_filter(struct lock_class *class)
- {
- #if 0
- /* Example */
- if (class->name_version == 1 &&
- !strcmp(class->name, "lockname"))
- return 1;
- if (class->name_version == 1 &&
- !strcmp(class->name, "&struct->lockfield"))
- return 1;
- #endif
- /* Filter everything else. 1 would be to allow everything else */
- return 0;
- }
- #endif
- static int verbose(struct lock_class *class)
- {
- #if VERBOSE
- return class_filter(class);
- #endif
- return 0;
- }
- static void print_lockdep_off(const char *bug_msg)
- {
- printk(KERN_DEBUG "%s\n", bug_msg);
- printk(KERN_DEBUG "turning off the locking correctness validator.\n");
- #ifdef CONFIG_LOCK_STAT
- printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
- #endif
- }
- unsigned long nr_stack_trace_entries;
- #ifdef CONFIG_PROVE_LOCKING
- /**
- * struct lock_trace - single stack backtrace
- * @hash_entry: Entry in a stack_trace_hash[] list.
- * @hash: jhash() of @entries.
- * @nr_entries: Number of entries in @entries.
- * @entries: Actual stack backtrace.
- */
- struct lock_trace {
- struct hlist_node hash_entry;
- u32 hash;
- u32 nr_entries;
- unsigned long entries[] __aligned(sizeof(unsigned long));
- };
- #define LOCK_TRACE_SIZE_IN_LONGS \
- (sizeof(struct lock_trace) / sizeof(unsigned long))
- /*
- * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
- */
- static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
- static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
- static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
- {
- return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
- memcmp(t1->entries, t2->entries,
- t1->nr_entries * sizeof(t1->entries[0])) == 0;
- }
- static struct lock_trace *save_trace(void)
- {
- struct lock_trace *trace, *t2;
- struct hlist_head *hash_head;
- u32 hash;
- int max_entries;
- BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
- BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
- trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
- max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
- LOCK_TRACE_SIZE_IN_LONGS;
- if (max_entries <= 0) {
- if (!debug_locks_off_graph_unlock())
- return NULL;
- print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
- dump_stack();
- return NULL;
- }
- trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
- hash = jhash(trace->entries, trace->nr_entries *
- sizeof(trace->entries[0]), 0);
- trace->hash = hash;
- hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
- hlist_for_each_entry(t2, hash_head, hash_entry) {
- if (traces_identical(trace, t2))
- return t2;
- }
- nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
- hlist_add_head(&trace->hash_entry, hash_head);
- return trace;
- }
- /* Return the number of stack traces in the stack_trace[] array. */
- u64 lockdep_stack_trace_count(void)
- {
- struct lock_trace *trace;
- u64 c = 0;
- int i;
- for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
- hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
- c++;
- }
- }
- return c;
- }
- /* Return the number of stack hash chains that have at least one stack trace. */
- u64 lockdep_stack_hash_count(void)
- {
- u64 c = 0;
- int i;
- for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
- if (!hlist_empty(&stack_trace_hash[i]))
- c++;
- return c;
- }
- #endif
- unsigned int nr_hardirq_chains;
- unsigned int nr_softirq_chains;
- unsigned int nr_process_chains;
- unsigned int max_lockdep_depth;
- #ifdef CONFIG_DEBUG_LOCKDEP
- /*
- * Various lockdep statistics:
- */
- DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
- #endif
- #ifdef CONFIG_PROVE_LOCKING
- /*
- * Locking printouts:
- */
- #define __USAGE(__STATE) \
- [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
- [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
- [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
- [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
- static const char *usage_str[] =
- {
- #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
- #include "lockdep_states.h"
- #undef LOCKDEP_STATE
- [LOCK_USED] = "INITIAL USE",
- [LOCK_USED_READ] = "INITIAL READ USE",
- /* abused as string storage for verify_lock_unused() */
- [LOCK_USAGE_STATES] = "IN-NMI",
- };
- #endif
- const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
- {
- return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
- }
- static inline unsigned long lock_flag(enum lock_usage_bit bit)
- {
- return 1UL << bit;
- }
- static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
- {
- /*
- * The usage character defaults to '.' (i.e., irqs disabled and not in
- * irq context), which is the safest usage category.
- */
- char c = '.';
- /*
- * The order of the following usage checks matters, which will
- * result in the outcome character as follows:
- *
- * - '+': irq is enabled and not in irq context
- * - '-': in irq context and irq is disabled
- * - '?': in irq context and irq is enabled
- */
- if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
- c = '+';
- if (class->usage_mask & lock_flag(bit))
- c = '?';
- } else if (class->usage_mask & lock_flag(bit))
- c = '-';
- return c;
- }
- void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
- {
- int i = 0;
- #define LOCKDEP_STATE(__STATE) \
- usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
- usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
- #include "lockdep_states.h"
- #undef LOCKDEP_STATE
- usage[i] = '\0';
- }
- static void __print_lock_name(struct lock_class *class)
- {
- char str[KSYM_NAME_LEN];
- const char *name;
- name = class->name;
- if (!name) {
- name = __get_key_name(class->key, str);
- printk(KERN_CONT "%s", name);
- } else {
- printk(KERN_CONT "%s", name);
- if (class->name_version > 1)
- printk(KERN_CONT "#%d", class->name_version);
- if (class->subclass)
- printk(KERN_CONT "/%d", class->subclass);
- }
- }
- static void print_lock_name(struct lock_class *class)
- {
- char usage[LOCK_USAGE_CHARS];
- get_usage_chars(class, usage);
- printk(KERN_CONT " (");
- __print_lock_name(class);
- printk(KERN_CONT "){%s}-{%d:%d}", usage,
- class->wait_type_outer ?: class->wait_type_inner,
- class->wait_type_inner);
- }
- static void print_lockdep_cache(struct lockdep_map *lock)
- {
- const char *name;
- char str[KSYM_NAME_LEN];
- name = lock->name;
- if (!name)
- name = __get_key_name(lock->key->subkeys, str);
- printk(KERN_CONT "%s", name);
- }
- static void print_lock(struct held_lock *hlock)
- {
- /*
- * We can be called locklessly through debug_show_all_locks() so be
- * extra careful, the hlock might have been released and cleared.
- *
- * If this indeed happens, lets pretend it does not hurt to continue
- * to print the lock unless the hlock class_idx does not point to a
- * registered class. The rationale here is: since we don't attempt
- * to distinguish whether we are in this situation, if it just
- * happened we can't count on class_idx to tell either.
- */
- struct lock_class *lock = hlock_class(hlock);
- if (!lock) {
- printk(KERN_CONT "<RELEASED>\n");
- return;
- }
- printk(KERN_CONT "%px", hlock->instance);
- print_lock_name(lock);
- printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
- }
- static void lockdep_print_held_locks(struct task_struct *p)
- {
- int i, depth = READ_ONCE(p->lockdep_depth);
- if (!depth)
- printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
- else
- printk("%d lock%s held by %s/%d:\n", depth,
- depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
- /*
- * It's not reliable to print a task's held locks if it's not sleeping
- * and it's not the current task.
- */
- if (p != current && task_is_running(p))
- return;
- for (i = 0; i < depth; i++) {
- printk(" #%d: ", i);
- print_lock(p->held_locks + i);
- }
- }
- static void print_kernel_ident(void)
- {
- printk("%s %.*s %s\n", init_utsname()->release,
- (int)strcspn(init_utsname()->version, " "),
- init_utsname()->version,
- print_tainted());
- }
- static int very_verbose(struct lock_class *class)
- {
- #if VERY_VERBOSE
- return class_filter(class);
- #endif
- return 0;
- }
- /*
- * Is this the address of a static object:
- */
- #ifdef __KERNEL__
- static int static_obj(const void *obj)
- {
- unsigned long addr = (unsigned long) obj;
- if (is_kernel_core_data(addr))
- return 1;
- /*
- * keys are allowed in the __ro_after_init section.
- */
- if (is_kernel_rodata(addr))
- return 1;
- /*
- * in initdata section and used during bootup only?
- * NOTE: On some platforms the initdata section is
- * outside of the _stext ... _end range.
- */
- if (system_state < SYSTEM_FREEING_INITMEM &&
- init_section_contains((void *)addr, 1))
- return 1;
- /*
- * in-kernel percpu var?
- */
- if (is_kernel_percpu_address(addr))
- return 1;
- /*
- * module static or percpu var?
- */
- return is_module_address(addr) || is_module_percpu_address(addr);
- }
- #endif
- /*
- * To make lock name printouts unique, we calculate a unique
- * class->name_version generation counter. The caller must hold the graph
- * lock.
- */
- static int count_matching_names(struct lock_class *new_class)
- {
- struct lock_class *class;
- int count = 0;
- if (!new_class->name)
- return 0;
- list_for_each_entry(class, &all_lock_classes, lock_entry) {
- if (new_class->key - new_class->subclass == class->key)
- return class->name_version;
- if (class->name && !strcmp(class->name, new_class->name))
- count = max(count, class->name_version);
- }
- return count + 1;
- }
- /* used from NMI context -- must be lockless */
- static noinstr struct lock_class *
- look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
- {
- struct lockdep_subclass_key *key;
- struct hlist_head *hash_head;
- struct lock_class *class;
- if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
- instrumentation_begin();
- debug_locks_off();
- printk(KERN_ERR
- "BUG: looking up invalid subclass: %u\n", subclass);
- printk(KERN_ERR
- "turning off the locking correctness validator.\n");
- dump_stack();
- instrumentation_end();
- return NULL;
- }
- /*
- * If it is not initialised then it has never been locked,
- * so it won't be present in the hash table.
- */
- if (unlikely(!lock->key))
- return NULL;
- /*
- * NOTE: the class-key must be unique. For dynamic locks, a static
- * lock_class_key variable is passed in through the mutex_init()
- * (or spin_lock_init()) call - which acts as the key. For static
- * locks we use the lock object itself as the key.
- */
- BUILD_BUG_ON(sizeof(struct lock_class_key) >
- sizeof(struct lockdep_map));
- key = lock->key->subkeys + subclass;
- hash_head = classhashentry(key);
- /*
- * We do an RCU walk of the hash, see lockdep_free_key_range().
- */
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return NULL;
- hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
- if (class->key == key) {
- /*
- * Huh! same key, different name? Did someone trample
- * on some memory? We're most confused.
- */
- WARN_ONCE(class->name != lock->name &&
- lock->key != &__lockdep_no_validate__,
- "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n",
- lock->name, lock->key, class->name);
- return class;
- }
- }
- return NULL;
- }
- /*
- * Static locks do not have their class-keys yet - for them the key is
- * the lock object itself. If the lock is in the per cpu area, the
- * canonical address of the lock (per cpu offset removed) is used.
- */
- static bool assign_lock_key(struct lockdep_map *lock)
- {
- unsigned long can_addr, addr = (unsigned long)lock;
- #ifdef __KERNEL__
- /*
- * lockdep_free_key_range() assumes that struct lock_class_key
- * objects do not overlap. Since we use the address of lock
- * objects as class key for static objects, check whether the
- * size of lock_class_key objects does not exceed the size of
- * the smallest lock object.
- */
- BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
- #endif
- if (__is_kernel_percpu_address(addr, &can_addr))
- lock->key = (void *)can_addr;
- else if (__is_module_percpu_address(addr, &can_addr))
- lock->key = (void *)can_addr;
- else if (static_obj(lock))
- lock->key = (void *)lock;
- else {
- /* Debug-check: all keys must be persistent! */
- debug_locks_off();
- pr_err("INFO: trying to register non-static key.\n");
- pr_err("The code is fine but needs lockdep annotation, or maybe\n");
- pr_err("you didn't initialize this object before use?\n");
- pr_err("turning off the locking correctness validator.\n");
- dump_stack();
- return false;
- }
- return true;
- }
- #ifdef CONFIG_DEBUG_LOCKDEP
- /* Check whether element @e occurs in list @h */
- static bool in_list(struct list_head *e, struct list_head *h)
- {
- struct list_head *f;
- list_for_each(f, h) {
- if (e == f)
- return true;
- }
- return false;
- }
- /*
- * Check whether entry @e occurs in any of the locks_after or locks_before
- * lists.
- */
- static bool in_any_class_list(struct list_head *e)
- {
- struct lock_class *class;
- int i;
- for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
- class = &lock_classes[i];
- if (in_list(e, &class->locks_after) ||
- in_list(e, &class->locks_before))
- return true;
- }
- return false;
- }
- static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
- {
- struct lock_list *e;
- list_for_each_entry(e, h, entry) {
- if (e->links_to != c) {
- printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
- c->name ? : "(?)",
- (unsigned long)(e - list_entries),
- e->links_to && e->links_to->name ?
- e->links_to->name : "(?)",
- e->class && e->class->name ? e->class->name :
- "(?)");
- return false;
- }
- }
- return true;
- }
- #ifdef CONFIG_PROVE_LOCKING
- static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
- #endif
- static bool check_lock_chain_key(struct lock_chain *chain)
- {
- #ifdef CONFIG_PROVE_LOCKING
- u64 chain_key = INITIAL_CHAIN_KEY;
- int i;
- for (i = chain->base; i < chain->base + chain->depth; i++)
- chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
- /*
- * The 'unsigned long long' casts avoid that a compiler warning
- * is reported when building tools/lib/lockdep.
- */
- if (chain->chain_key != chain_key) {
- printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
- (unsigned long long)(chain - lock_chains),
- (unsigned long long)chain->chain_key,
- (unsigned long long)chain_key);
- return false;
- }
- #endif
- return true;
- }
- static bool in_any_zapped_class_list(struct lock_class *class)
- {
- struct pending_free *pf;
- int i;
- for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
- if (in_list(&class->lock_entry, &pf->zapped))
- return true;
- }
- return false;
- }
- static bool __check_data_structures(void)
- {
- struct lock_class *class;
- struct lock_chain *chain;
- struct hlist_head *head;
- struct lock_list *e;
- int i;
- /* Check whether all classes occur in a lock list. */
- for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
- class = &lock_classes[i];
- if (!in_list(&class->lock_entry, &all_lock_classes) &&
- !in_list(&class->lock_entry, &free_lock_classes) &&
- !in_any_zapped_class_list(class)) {
- printk(KERN_INFO "class %px/%s is not in any class list\n",
- class, class->name ? : "(?)");
- return false;
- }
- }
- /* Check whether all classes have valid lock lists. */
- for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
- class = &lock_classes[i];
- if (!class_lock_list_valid(class, &class->locks_before))
- return false;
- if (!class_lock_list_valid(class, &class->locks_after))
- return false;
- }
- /* Check the chain_key of all lock chains. */
- for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
- head = chainhash_table + i;
- hlist_for_each_entry_rcu(chain, head, entry) {
- if (!check_lock_chain_key(chain))
- return false;
- }
- }
- /*
- * Check whether all list entries that are in use occur in a class
- * lock list.
- */
- for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
- e = list_entries + i;
- if (!in_any_class_list(&e->entry)) {
- printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
- (unsigned int)(e - list_entries),
- e->class->name ? : "(?)",
- e->links_to->name ? : "(?)");
- return false;
- }
- }
- /*
- * Check whether all list entries that are not in use do not occur in
- * a class lock list.
- */
- for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
- e = list_entries + i;
- if (in_any_class_list(&e->entry)) {
- printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
- (unsigned int)(e - list_entries),
- e->class && e->class->name ? e->class->name :
- "(?)",
- e->links_to && e->links_to->name ?
- e->links_to->name : "(?)");
- return false;
- }
- }
- return true;
- }
- int check_consistency = 0;
- module_param(check_consistency, int, 0644);
- static void check_data_structures(void)
- {
- static bool once = false;
- if (check_consistency && !once) {
- if (!__check_data_structures()) {
- once = true;
- WARN_ON(once);
- }
- }
- }
- #else /* CONFIG_DEBUG_LOCKDEP */
- static inline void check_data_structures(void) { }
- #endif /* CONFIG_DEBUG_LOCKDEP */
- static void init_chain_block_buckets(void);
- /*
- * Initialize the lock_classes[] array elements, the free_lock_classes list
- * and also the delayed_free structure.
- */
- static void init_data_structures_once(void)
- {
- static bool __read_mostly ds_initialized, rcu_head_initialized;
- int i;
- if (likely(rcu_head_initialized))
- return;
- if (system_state >= SYSTEM_SCHEDULING) {
- init_rcu_head(&delayed_free.rcu_head);
- rcu_head_initialized = true;
- }
- if (ds_initialized)
- return;
- ds_initialized = true;
- INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
- INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
- for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
- list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
- INIT_LIST_HEAD(&lock_classes[i].locks_after);
- INIT_LIST_HEAD(&lock_classes[i].locks_before);
- }
- init_chain_block_buckets();
- }
- static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
- {
- unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
- return lock_keys_hash + hash;
- }
- /* Register a dynamically allocated key. */
- void lockdep_register_key(struct lock_class_key *key)
- {
- struct hlist_head *hash_head;
- struct lock_class_key *k;
- unsigned long flags;
- if (WARN_ON_ONCE(static_obj(key)))
- return;
- hash_head = keyhashentry(key);
- raw_local_irq_save(flags);
- if (!graph_lock())
- goto restore_irqs;
- hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
- if (WARN_ON_ONCE(k == key))
- goto out_unlock;
- }
- hlist_add_head_rcu(&key->hash_entry, hash_head);
- out_unlock:
- graph_unlock();
- restore_irqs:
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lockdep_register_key);
- /* Check whether a key has been registered as a dynamic key. */
- static bool is_dynamic_key(const struct lock_class_key *key)
- {
- struct hlist_head *hash_head;
- struct lock_class_key *k;
- bool found = false;
- if (WARN_ON_ONCE(static_obj(key)))
- return false;
- /*
- * If lock debugging is disabled lock_keys_hash[] may contain
- * pointers to memory that has already been freed. Avoid triggering
- * a use-after-free in that case by returning early.
- */
- if (!debug_locks)
- return true;
- hash_head = keyhashentry(key);
- rcu_read_lock();
- hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
- if (k == key) {
- found = true;
- break;
- }
- }
- rcu_read_unlock();
- return found;
- }
- /*
- * Register a lock's class in the hash-table, if the class is not present
- * yet. Otherwise we look it up. We cache the result in the lock object
- * itself, so actual lookup of the hash should be once per lock object.
- */
- static struct lock_class *
- register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
- {
- struct lockdep_subclass_key *key;
- struct hlist_head *hash_head;
- struct lock_class *class;
- int idx;
- DEBUG_LOCKS_WARN_ON(!irqs_disabled());
- class = look_up_lock_class(lock, subclass);
- if (likely(class))
- goto out_set_class_cache;
- if (!lock->key) {
- if (!assign_lock_key(lock))
- return NULL;
- } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
- return NULL;
- }
- key = lock->key->subkeys + subclass;
- hash_head = classhashentry(key);
- if (!graph_lock()) {
- return NULL;
- }
- /*
- * We have to do the hash-walk again, to avoid races
- * with another CPU:
- */
- hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
- if (class->key == key)
- goto out_unlock_set;
- }
- init_data_structures_once();
- /* Allocate a new lock class and add it to the hash. */
- class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
- lock_entry);
- if (!class) {
- if (!debug_locks_off_graph_unlock()) {
- return NULL;
- }
- print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
- dump_stack();
- return NULL;
- }
- nr_lock_classes++;
- __set_bit(class - lock_classes, lock_classes_in_use);
- debug_atomic_inc(nr_unused_locks);
- class->key = key;
- class->name = lock->name;
- class->subclass = subclass;
- WARN_ON_ONCE(!list_empty(&class->locks_before));
- WARN_ON_ONCE(!list_empty(&class->locks_after));
- class->name_version = count_matching_names(class);
- class->wait_type_inner = lock->wait_type_inner;
- class->wait_type_outer = lock->wait_type_outer;
- class->lock_type = lock->lock_type;
- /*
- * We use RCU's safe list-add method to make
- * parallel walking of the hash-list safe:
- */
- hlist_add_head_rcu(&class->hash_entry, hash_head);
- /*
- * Remove the class from the free list and add it to the global list
- * of classes.
- */
- list_move_tail(&class->lock_entry, &all_lock_classes);
- idx = class - lock_classes;
- if (idx > max_lock_class_idx)
- max_lock_class_idx = idx;
- if (verbose(class)) {
- graph_unlock();
- printk("\nnew class %px: %s", class->key, class->name);
- if (class->name_version > 1)
- printk(KERN_CONT "#%d", class->name_version);
- printk(KERN_CONT "\n");
- dump_stack();
- if (!graph_lock()) {
- return NULL;
- }
- }
- out_unlock_set:
- graph_unlock();
- out_set_class_cache:
- if (!subclass || force)
- lock->class_cache[0] = class;
- else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
- lock->class_cache[subclass] = class;
- /*
- * Hash collision, did we smoke some? We found a class with a matching
- * hash but the subclass -- which is hashed in -- didn't match.
- */
- if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
- return NULL;
- return class;
- }
- #ifdef CONFIG_PROVE_LOCKING
- /*
- * Allocate a lockdep entry. (assumes the graph_lock held, returns
- * with NULL on failure)
- */
- static struct lock_list *alloc_list_entry(void)
- {
- int idx = find_first_zero_bit(list_entries_in_use,
- ARRAY_SIZE(list_entries));
- if (idx >= ARRAY_SIZE(list_entries)) {
- if (!debug_locks_off_graph_unlock())
- return NULL;
- print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
- dump_stack();
- return NULL;
- }
- nr_list_entries++;
- __set_bit(idx, list_entries_in_use);
- return list_entries + idx;
- }
- /*
- * Add a new dependency to the head of the list:
- */
- static int add_lock_to_list(struct lock_class *this,
- struct lock_class *links_to, struct list_head *head,
- u16 distance, u8 dep,
- const struct lock_trace *trace)
- {
- struct lock_list *entry;
- /*
- * Lock not present yet - get a new dependency struct and
- * add it to the list:
- */
- entry = alloc_list_entry();
- if (!entry)
- return 0;
- entry->class = this;
- entry->links_to = links_to;
- entry->dep = dep;
- entry->distance = distance;
- entry->trace = trace;
- /*
- * Both allocation and removal are done under the graph lock; but
- * iteration is under RCU-sched; see look_up_lock_class() and
- * lockdep_free_key_range().
- */
- list_add_tail_rcu(&entry->entry, head);
- return 1;
- }
- /*
- * For good efficiency of modular, we use power of 2
- */
- #define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
- #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
- /*
- * The circular_queue and helpers are used to implement graph
- * breadth-first search (BFS) algorithm, by which we can determine
- * whether there is a path from a lock to another. In deadlock checks,
- * a path from the next lock to be acquired to a previous held lock
- * indicates that adding the <prev> -> <next> lock dependency will
- * produce a circle in the graph. Breadth-first search instead of
- * depth-first search is used in order to find the shortest (circular)
- * path.
- */
- struct circular_queue {
- struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
- unsigned int front, rear;
- };
- static struct circular_queue lock_cq;
- unsigned int max_bfs_queue_depth;
- static unsigned int lockdep_dependency_gen_id;
- static inline void __cq_init(struct circular_queue *cq)
- {
- cq->front = cq->rear = 0;
- lockdep_dependency_gen_id++;
- }
- static inline int __cq_empty(struct circular_queue *cq)
- {
- return (cq->front == cq->rear);
- }
- static inline int __cq_full(struct circular_queue *cq)
- {
- return ((cq->rear + 1) & CQ_MASK) == cq->front;
- }
- static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
- {
- if (__cq_full(cq))
- return -1;
- cq->element[cq->rear] = elem;
- cq->rear = (cq->rear + 1) & CQ_MASK;
- return 0;
- }
- /*
- * Dequeue an element from the circular_queue, return a lock_list if
- * the queue is not empty, or NULL if otherwise.
- */
- static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
- {
- struct lock_list * lock;
- if (__cq_empty(cq))
- return NULL;
- lock = cq->element[cq->front];
- cq->front = (cq->front + 1) & CQ_MASK;
- return lock;
- }
- static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
- {
- return (cq->rear - cq->front) & CQ_MASK;
- }
- static inline void mark_lock_accessed(struct lock_list *lock)
- {
- lock->class->dep_gen_id = lockdep_dependency_gen_id;
- }
- static inline void visit_lock_entry(struct lock_list *lock,
- struct lock_list *parent)
- {
- lock->parent = parent;
- }
- static inline unsigned long lock_accessed(struct lock_list *lock)
- {
- return lock->class->dep_gen_id == lockdep_dependency_gen_id;
- }
- static inline struct lock_list *get_lock_parent(struct lock_list *child)
- {
- return child->parent;
- }
- static inline int get_lock_depth(struct lock_list *child)
- {
- int depth = 0;
- struct lock_list *parent;
- while ((parent = get_lock_parent(child))) {
- child = parent;
- depth++;
- }
- return depth;
- }
- /*
- * Return the forward or backward dependency list.
- *
- * @lock: the lock_list to get its class's dependency list
- * @offset: the offset to struct lock_class to determine whether it is
- * locks_after or locks_before
- */
- static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
- {
- void *lock_class = lock->class;
- return lock_class + offset;
- }
- /*
- * Return values of a bfs search:
- *
- * BFS_E* indicates an error
- * BFS_R* indicates a result (match or not)
- *
- * BFS_EINVALIDNODE: Find a invalid node in the graph.
- *
- * BFS_EQUEUEFULL: The queue is full while doing the bfs.
- *
- * BFS_RMATCH: Find the matched node in the graph, and put that node into
- * *@target_entry.
- *
- * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
- * _unchanged_.
- */
- enum bfs_result {
- BFS_EINVALIDNODE = -2,
- BFS_EQUEUEFULL = -1,
- BFS_RMATCH = 0,
- BFS_RNOMATCH = 1,
- };
- /*
- * bfs_result < 0 means error
- */
- static inline bool bfs_error(enum bfs_result res)
- {
- return res < 0;
- }
- /*
- * DEP_*_BIT in lock_list::dep
- *
- * For dependency @prev -> @next:
- *
- * SR: @prev is shared reader (->read != 0) and @next is recursive reader
- * (->read == 2)
- * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
- * SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
- * EN: @prev is exclusive locker and @next is non-recursive locker
- *
- * Note that we define the value of DEP_*_BITs so that:
- * bit0 is prev->read == 0
- * bit1 is next->read != 2
- */
- #define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
- #define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
- #define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
- #define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
- #define DEP_SR_MASK (1U << (DEP_SR_BIT))
- #define DEP_ER_MASK (1U << (DEP_ER_BIT))
- #define DEP_SN_MASK (1U << (DEP_SN_BIT))
- #define DEP_EN_MASK (1U << (DEP_EN_BIT))
- static inline unsigned int
- __calc_dep_bit(struct held_lock *prev, struct held_lock *next)
- {
- return (prev->read == 0) + ((next->read != 2) << 1);
- }
- static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
- {
- return 1U << __calc_dep_bit(prev, next);
- }
- /*
- * calculate the dep_bit for backwards edges. We care about whether @prev is
- * shared and whether @next is recursive.
- */
- static inline unsigned int
- __calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
- {
- return (next->read != 2) + ((prev->read == 0) << 1);
- }
- static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
- {
- return 1U << __calc_dep_bitb(prev, next);
- }
- /*
- * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
- * search.
- */
- static inline void __bfs_init_root(struct lock_list *lock,
- struct lock_class *class)
- {
- lock->class = class;
- lock->parent = NULL;
- lock->only_xr = 0;
- }
- /*
- * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
- * root for a BFS search.
- *
- * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
- * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
- * and -(S*)->.
- */
- static inline void bfs_init_root(struct lock_list *lock,
- struct held_lock *hlock)
- {
- __bfs_init_root(lock, hlock_class(hlock));
- lock->only_xr = (hlock->read == 2);
- }
- /*
- * Similar to bfs_init_root() but initialize the root for backwards BFS.
- *
- * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
- * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
- * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
- */
- static inline void bfs_init_rootb(struct lock_list *lock,
- struct held_lock *hlock)
- {
- __bfs_init_root(lock, hlock_class(hlock));
- lock->only_xr = (hlock->read != 0);
- }
- static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
- {
- if (!lock || !lock->parent)
- return NULL;
- return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
- &lock->entry, struct lock_list, entry);
- }
- /*
- * Breadth-First Search to find a strong path in the dependency graph.
- *
- * @source_entry: the source of the path we are searching for.
- * @data: data used for the second parameter of @match function
- * @match: match function for the search
- * @target_entry: pointer to the target of a matched path
- * @offset: the offset to struct lock_class to determine whether it is
- * locks_after or locks_before
- *
- * We may have multiple edges (considering different kinds of dependencies,
- * e.g. ER and SN) between two nodes in the dependency graph. But
- * only the strong dependency path in the graph is relevant to deadlocks. A
- * strong dependency path is a dependency path that doesn't have two adjacent
- * dependencies as -(*R)-> -(S*)->, please see:
- *
- * Documentation/locking/lockdep-design.rst
- *
- * for more explanation of the definition of strong dependency paths
- *
- * In __bfs(), we only traverse in the strong dependency path:
- *
- * In lock_list::only_xr, we record whether the previous dependency only
- * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
- * filter out any -(S*)-> in the current dependency and after that, the
- * ->only_xr is set according to whether we only have -(*R)-> left.
- */
- static enum bfs_result __bfs(struct lock_list *source_entry,
- void *data,
- bool (*match)(struct lock_list *entry, void *data),
- bool (*skip)(struct lock_list *entry, void *data),
- struct lock_list **target_entry,
- int offset)
- {
- struct circular_queue *cq = &lock_cq;
- struct lock_list *lock = NULL;
- struct lock_list *entry;
- struct list_head *head;
- unsigned int cq_depth;
- bool first;
- lockdep_assert_locked();
- __cq_init(cq);
- __cq_enqueue(cq, source_entry);
- while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
- if (!lock->class)
- return BFS_EINVALIDNODE;
- /*
- * Step 1: check whether we already finish on this one.
- *
- * If we have visited all the dependencies from this @lock to
- * others (iow, if we have visited all lock_list entries in
- * @lock->class->locks_{after,before}) we skip, otherwise go
- * and visit all the dependencies in the list and mark this
- * list accessed.
- */
- if (lock_accessed(lock))
- continue;
- else
- mark_lock_accessed(lock);
- /*
- * Step 2: check whether prev dependency and this form a strong
- * dependency path.
- */
- if (lock->parent) { /* Parent exists, check prev dependency */
- u8 dep = lock->dep;
- bool prev_only_xr = lock->parent->only_xr;
- /*
- * Mask out all -(S*)-> if we only have *R in previous
- * step, because -(*R)-> -(S*)-> don't make up a strong
- * dependency.
- */
- if (prev_only_xr)
- dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
- /* If nothing left, we skip */
- if (!dep)
- continue;
- /* If there are only -(*R)-> left, set that for the next step */
- lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
- }
- /*
- * Step 3: we haven't visited this and there is a strong
- * dependency path to this, so check with @match.
- * If @skip is provide and returns true, we skip this
- * lock (and any path this lock is in).
- */
- if (skip && skip(lock, data))
- continue;
- if (match(lock, data)) {
- *target_entry = lock;
- return BFS_RMATCH;
- }
- /*
- * Step 4: if not match, expand the path by adding the
- * forward or backwards dependencies in the search
- *
- */
- first = true;
- head = get_dep_list(lock, offset);
- list_for_each_entry_rcu(entry, head, entry) {
- visit_lock_entry(entry, lock);
- /*
- * Note we only enqueue the first of the list into the
- * queue, because we can always find a sibling
- * dependency from one (see __bfs_next()), as a result
- * the space of queue is saved.
- */
- if (!first)
- continue;
- first = false;
- if (__cq_enqueue(cq, entry))
- return BFS_EQUEUEFULL;
- cq_depth = __cq_get_elem_count(cq);
- if (max_bfs_queue_depth < cq_depth)
- max_bfs_queue_depth = cq_depth;
- }
- }
- return BFS_RNOMATCH;
- }
- static inline enum bfs_result
- __bfs_forwards(struct lock_list *src_entry,
- void *data,
- bool (*match)(struct lock_list *entry, void *data),
- bool (*skip)(struct lock_list *entry, void *data),
- struct lock_list **target_entry)
- {
- return __bfs(src_entry, data, match, skip, target_entry,
- offsetof(struct lock_class, locks_after));
- }
- static inline enum bfs_result
- __bfs_backwards(struct lock_list *src_entry,
- void *data,
- bool (*match)(struct lock_list *entry, void *data),
- bool (*skip)(struct lock_list *entry, void *data),
- struct lock_list **target_entry)
- {
- return __bfs(src_entry, data, match, skip, target_entry,
- offsetof(struct lock_class, locks_before));
- }
- static void print_lock_trace(const struct lock_trace *trace,
- unsigned int spaces)
- {
- stack_trace_print(trace->entries, trace->nr_entries, spaces);
- }
- /*
- * Print a dependency chain entry (this is only done when a deadlock
- * has been detected):
- */
- static noinline void
- print_circular_bug_entry(struct lock_list *target, int depth)
- {
- if (debug_locks_silent)
- return;
- printk("\n-> #%u", depth);
- print_lock_name(target->class);
- printk(KERN_CONT ":\n");
- print_lock_trace(target->trace, 6);
- }
- static void
- print_circular_lock_scenario(struct held_lock *src,
- struct held_lock *tgt,
- struct lock_list *prt)
- {
- struct lock_class *source = hlock_class(src);
- struct lock_class *target = hlock_class(tgt);
- struct lock_class *parent = prt->class;
- /*
- * A direct locking problem where unsafe_class lock is taken
- * directly by safe_class lock, then all we need to show
- * is the deadlock scenario, as it is obvious that the
- * unsafe lock is taken under the safe lock.
- *
- * But if there is a chain instead, where the safe lock takes
- * an intermediate lock (middle_class) where this lock is
- * not the same as the safe lock, then the lock chain is
- * used to describe the problem. Otherwise we would need
- * to show a different CPU case for each link in the chain
- * from the safe_class lock to the unsafe_class lock.
- */
- if (parent != source) {
- printk("Chain exists of:\n ");
- __print_lock_name(source);
- printk(KERN_CONT " --> ");
- __print_lock_name(parent);
- printk(KERN_CONT " --> ");
- __print_lock_name(target);
- printk(KERN_CONT "\n\n");
- }
- printk(" Possible unsafe locking scenario:\n\n");
- printk(" CPU0 CPU1\n");
- printk(" ---- ----\n");
- printk(" lock(");
- __print_lock_name(target);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(parent);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(target);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(source);
- printk(KERN_CONT ");\n");
- printk("\n *** DEADLOCK ***\n\n");
- }
- /*
- * When a circular dependency is detected, print the
- * header first:
- */
- static noinline void
- print_circular_bug_header(struct lock_list *entry, unsigned int depth,
- struct held_lock *check_src,
- struct held_lock *check_tgt)
- {
- struct task_struct *curr = current;
- if (debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("======================================================\n");
- pr_warn("WARNING: possible circular locking dependency detected\n");
- print_kernel_ident();
- pr_warn("------------------------------------------------------\n");
- pr_warn("%s/%d is trying to acquire lock:\n",
- curr->comm, task_pid_nr(curr));
- print_lock(check_src);
- pr_warn("\nbut task is already holding lock:\n");
- print_lock(check_tgt);
- pr_warn("\nwhich lock already depends on the new lock.\n\n");
- pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
- print_circular_bug_entry(entry, depth);
- }
- /*
- * We are about to add A -> B into the dependency graph, and in __bfs() a
- * strong dependency path A -> .. -> B is found: hlock_class equals
- * entry->class.
- *
- * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
- * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
- * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
- * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
- * dependency graph, as any strong path ..-> A -> B ->.. we can get with
- * having dependency A -> B, we could already get a equivalent path ..-> A ->
- * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant.
- *
- * We need to make sure both the start and the end of A -> .. -> B is not
- * weaker than A -> B. For the start part, please see the comment in
- * check_redundant(). For the end part, we need:
- *
- * Either
- *
- * a) A -> B is -(*R)-> (everything is not weaker than that)
- *
- * or
- *
- * b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
- *
- */
- static inline bool hlock_equal(struct lock_list *entry, void *data)
- {
- struct held_lock *hlock = (struct held_lock *)data;
- return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
- (hlock->read == 2 || /* A -> B is -(*R)-> */
- !entry->only_xr); /* A -> .. -> B is -(*N)-> */
- }
- /*
- * We are about to add B -> A into the dependency graph, and in __bfs() a
- * strong dependency path A -> .. -> B is found: hlock_class equals
- * entry->class.
- *
- * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
- * dependency cycle, that means:
- *
- * Either
- *
- * a) B -> A is -(E*)->
- *
- * or
- *
- * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
- *
- * as then we don't have -(*R)-> -(S*)-> in the cycle.
- */
- static inline bool hlock_conflict(struct lock_list *entry, void *data)
- {
- struct held_lock *hlock = (struct held_lock *)data;
- return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
- (hlock->read == 0 || /* B -> A is -(E*)-> */
- !entry->only_xr); /* A -> .. -> B is -(*N)-> */
- }
- static noinline void print_circular_bug(struct lock_list *this,
- struct lock_list *target,
- struct held_lock *check_src,
- struct held_lock *check_tgt)
- {
- struct task_struct *curr = current;
- struct lock_list *parent;
- struct lock_list *first_parent;
- int depth;
- if (!debug_locks_off_graph_unlock() || debug_locks_silent)
- return;
- this->trace = save_trace();
- if (!this->trace)
- return;
- depth = get_lock_depth(target);
- print_circular_bug_header(target, depth, check_src, check_tgt);
- parent = get_lock_parent(target);
- first_parent = parent;
- while (parent) {
- print_circular_bug_entry(parent, --depth);
- parent = get_lock_parent(parent);
- }
- printk("\nother info that might help us debug this:\n\n");
- print_circular_lock_scenario(check_src, check_tgt,
- first_parent);
- lockdep_print_held_locks(curr);
- printk("\nstack backtrace:\n");
- dump_stack();
- }
- static noinline void print_bfs_bug(int ret)
- {
- if (!debug_locks_off_graph_unlock())
- return;
- /*
- * Breadth-first-search failed, graph got corrupted?
- */
- WARN(1, "lockdep bfs error:%d\n", ret);
- }
- static bool noop_count(struct lock_list *entry, void *data)
- {
- (*(unsigned long *)data)++;
- return false;
- }
- static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
- {
- unsigned long count = 0;
- struct lock_list *target_entry;
- __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
- return count;
- }
- unsigned long lockdep_count_forward_deps(struct lock_class *class)
- {
- unsigned long ret, flags;
- struct lock_list this;
- __bfs_init_root(&this, class);
- raw_local_irq_save(flags);
- lockdep_lock();
- ret = __lockdep_count_forward_deps(&this);
- lockdep_unlock();
- raw_local_irq_restore(flags);
- return ret;
- }
- static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
- {
- unsigned long count = 0;
- struct lock_list *target_entry;
- __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
- return count;
- }
- unsigned long lockdep_count_backward_deps(struct lock_class *class)
- {
- unsigned long ret, flags;
- struct lock_list this;
- __bfs_init_root(&this, class);
- raw_local_irq_save(flags);
- lockdep_lock();
- ret = __lockdep_count_backward_deps(&this);
- lockdep_unlock();
- raw_local_irq_restore(flags);
- return ret;
- }
- /*
- * Check that the dependency graph starting at <src> can lead to
- * <target> or not.
- */
- static noinline enum bfs_result
- check_path(struct held_lock *target, struct lock_list *src_entry,
- bool (*match)(struct lock_list *entry, void *data),
- bool (*skip)(struct lock_list *entry, void *data),
- struct lock_list **target_entry)
- {
- enum bfs_result ret;
- ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
- if (unlikely(bfs_error(ret)))
- print_bfs_bug(ret);
- return ret;
- }
- /*
- * Prove that the dependency graph starting at <src> can not
- * lead to <target>. If it can, there is a circle when adding
- * <target> -> <src> dependency.
- *
- * Print an error and return BFS_RMATCH if it does.
- */
- static noinline enum bfs_result
- check_noncircular(struct held_lock *src, struct held_lock *target,
- struct lock_trace **const trace)
- {
- enum bfs_result ret;
- struct lock_list *target_entry;
- struct lock_list src_entry;
- bfs_init_root(&src_entry, src);
- debug_atomic_inc(nr_cyclic_checks);
- ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
- if (unlikely(ret == BFS_RMATCH)) {
- if (!*trace) {
- /*
- * If save_trace fails here, the printing might
- * trigger a WARN but because of the !nr_entries it
- * should not do bad things.
- */
- *trace = save_trace();
- }
- print_circular_bug(&src_entry, target_entry, src, target);
- }
- return ret;
- }
- #ifdef CONFIG_TRACE_IRQFLAGS
- /*
- * Forwards and backwards subgraph searching, for the purposes of
- * proving that two subgraphs can be connected by a new dependency
- * without creating any illegal irq-safe -> irq-unsafe lock dependency.
- *
- * A irq safe->unsafe deadlock happens with the following conditions:
- *
- * 1) We have a strong dependency path A -> ... -> B
- *
- * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
- * irq can create a new dependency B -> A (consider the case that a holder
- * of B gets interrupted by an irq whose handler will try to acquire A).
- *
- * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
- * strong circle:
- *
- * For the usage bits of B:
- * a) if A -> B is -(*N)->, then B -> A could be any type, so any
- * ENABLED_IRQ usage suffices.
- * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
- * ENABLED_IRQ_*_READ usage suffices.
- *
- * For the usage bits of A:
- * c) if A -> B is -(E*)->, then B -> A could be any type, so any
- * USED_IN_IRQ usage suffices.
- * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
- * USED_IN_IRQ_*_READ usage suffices.
- */
- /*
- * There is a strong dependency path in the dependency graph: A -> B, and now
- * we need to decide which usage bit of A should be accumulated to detect
- * safe->unsafe bugs.
- *
- * Note that usage_accumulate() is used in backwards search, so ->only_xr
- * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
- *
- * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
- * path, any usage of A should be considered. Otherwise, we should only
- * consider _READ usage.
- */
- static inline bool usage_accumulate(struct lock_list *entry, void *mask)
- {
- if (!entry->only_xr)
- *(unsigned long *)mask |= entry->class->usage_mask;
- else /* Mask out _READ usage bits */
- *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
- return false;
- }
- /*
- * There is a strong dependency path in the dependency graph: A -> B, and now
- * we need to decide which usage bit of B conflicts with the usage bits of A,
- * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
- *
- * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
- * path, any usage of B should be considered. Otherwise, we should only
- * consider _READ usage.
- */
- static inline bool usage_match(struct lock_list *entry, void *mask)
- {
- if (!entry->only_xr)
- return !!(entry->class->usage_mask & *(unsigned long *)mask);
- else /* Mask out _READ usage bits */
- return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
- }
- static inline bool usage_skip(struct lock_list *entry, void *mask)
- {
- /*
- * Skip local_lock() for irq inversion detection.
- *
- * For !RT, local_lock() is not a real lock, so it won't carry any
- * dependency.
- *
- * For RT, an irq inversion happens when we have lock A and B, and on
- * some CPU we can have:
- *
- * lock(A);
- * <interrupted>
- * lock(B);
- *
- * where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
- *
- * Now we prove local_lock() cannot exist in that dependency. First we
- * have the observation for any lock chain L1 -> ... -> Ln, for any
- * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
- * wait context check will complain. And since B is not a sleep lock,
- * therefore B.inner_wait_type >= 2, and since the inner_wait_type of
- * local_lock() is 3, which is greater than 2, therefore there is no
- * way the local_lock() exists in the dependency B -> ... -> A.
- *
- * As a result, we will skip local_lock(), when we search for irq
- * inversion bugs.
- */
- if (entry->class->lock_type == LD_LOCK_PERCPU) {
- if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
- return false;
- return true;
- }
- return false;
- }
- /*
- * Find a node in the forwards-direction dependency sub-graph starting
- * at @root->class that matches @bit.
- *
- * Return BFS_MATCH if such a node exists in the subgraph, and put that node
- * into *@target_entry.
- */
- static enum bfs_result
- find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
- struct lock_list **target_entry)
- {
- enum bfs_result result;
- debug_atomic_inc(nr_find_usage_forwards_checks);
- result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
- return result;
- }
- /*
- * Find a node in the backwards-direction dependency sub-graph starting
- * at @root->class that matches @bit.
- */
- static enum bfs_result
- find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
- struct lock_list **target_entry)
- {
- enum bfs_result result;
- debug_atomic_inc(nr_find_usage_backwards_checks);
- result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
- return result;
- }
- static void print_lock_class_header(struct lock_class *class, int depth)
- {
- int bit;
- printk("%*s->", depth, "");
- print_lock_name(class);
- #ifdef CONFIG_DEBUG_LOCKDEP
- printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
- #endif
- printk(KERN_CONT " {\n");
- for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
- if (class->usage_mask & (1 << bit)) {
- int len = depth;
- len += printk("%*s %s", depth, "", usage_str[bit]);
- len += printk(KERN_CONT " at:\n");
- print_lock_trace(class->usage_traces[bit], len);
- }
- }
- printk("%*s }\n", depth, "");
- printk("%*s ... key at: [<%px>] %pS\n",
- depth, "", class->key, class->key);
- }
- /*
- * Dependency path printing:
- *
- * After BFS we get a lock dependency path (linked via ->parent of lock_list),
- * printing out each lock in the dependency path will help on understanding how
- * the deadlock could happen. Here are some details about dependency path
- * printing:
- *
- * 1) A lock_list can be either forwards or backwards for a lock dependency,
- * for a lock dependency A -> B, there are two lock_lists:
- *
- * a) lock_list in the ->locks_after list of A, whose ->class is B and
- * ->links_to is A. In this case, we can say the lock_list is
- * "A -> B" (forwards case).
- *
- * b) lock_list in the ->locks_before list of B, whose ->class is A
- * and ->links_to is B. In this case, we can say the lock_list is
- * "B <- A" (bacwards case).
- *
- * The ->trace of both a) and b) point to the call trace where B was
- * acquired with A held.
- *
- * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't
- * represent a certain lock dependency, it only provides an initial entry
- * for BFS. For example, BFS may introduce a "helper" lock_list whose
- * ->class is A, as a result BFS will search all dependencies starting with
- * A, e.g. A -> B or A -> C.
- *
- * The notation of a forwards helper lock_list is like "-> A", which means
- * we should search the forwards dependencies starting with "A", e.g A -> B
- * or A -> C.
- *
- * The notation of a bacwards helper lock_list is like "<- B", which means
- * we should search the backwards dependencies ending with "B", e.g.
- * B <- A or B <- C.
- */
- /*
- * printk the shortest lock dependencies from @root to @leaf in reverse order.
- *
- * We have a lock dependency path as follow:
- *
- * @root @leaf
- * | |
- * V V
- * ->parent ->parent
- * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list |
- * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln|
- *
- * , so it's natural that we start from @leaf and print every ->class and
- * ->trace until we reach the @root.
- */
- static void __used
- print_shortest_lock_dependencies(struct lock_list *leaf,
- struct lock_list *root)
- {
- struct lock_list *entry = leaf;
- int depth;
- /*compute depth from generated tree by BFS*/
- depth = get_lock_depth(leaf);
- do {
- print_lock_class_header(entry->class, depth);
- printk("%*s ... acquired at:\n", depth, "");
- print_lock_trace(entry->trace, 2);
- printk("\n");
- if (depth == 0 && (entry != root)) {
- printk("lockdep:%s bad path found in chain graph\n", __func__);
- break;
- }
- entry = get_lock_parent(entry);
- depth--;
- } while (entry && (depth >= 0));
- }
- /*
- * printk the shortest lock dependencies from @leaf to @root.
- *
- * We have a lock dependency path (from a backwards search) as follow:
- *
- * @leaf @root
- * | |
- * V V
- * ->parent ->parent
- * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list |
- * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln |
- *
- * , so when we iterate from @leaf to @root, we actually print the lock
- * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
- *
- * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
- * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
- * trace of L1 in the dependency path, which is alright, because most of the
- * time we can figure out where L1 is held from the call trace of L2.
- */
- static void __used
- print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
- struct lock_list *root)
- {
- struct lock_list *entry = leaf;
- const struct lock_trace *trace = NULL;
- int depth;
- /*compute depth from generated tree by BFS*/
- depth = get_lock_depth(leaf);
- do {
- print_lock_class_header(entry->class, depth);
- if (trace) {
- printk("%*s ... acquired at:\n", depth, "");
- print_lock_trace(trace, 2);
- printk("\n");
- }
- /*
- * Record the pointer to the trace for the next lock_list
- * entry, see the comments for the function.
- */
- trace = entry->trace;
- if (depth == 0 && (entry != root)) {
- printk("lockdep:%s bad path found in chain graph\n", __func__);
- break;
- }
- entry = get_lock_parent(entry);
- depth--;
- } while (entry && (depth >= 0));
- }
- static void
- print_irq_lock_scenario(struct lock_list *safe_entry,
- struct lock_list *unsafe_entry,
- struct lock_class *prev_class,
- struct lock_class *next_class)
- {
- struct lock_class *safe_class = safe_entry->class;
- struct lock_class *unsafe_class = unsafe_entry->class;
- struct lock_class *middle_class = prev_class;
- if (middle_class == safe_class)
- middle_class = next_class;
- /*
- * A direct locking problem where unsafe_class lock is taken
- * directly by safe_class lock, then all we need to show
- * is the deadlock scenario, as it is obvious that the
- * unsafe lock is taken under the safe lock.
- *
- * But if there is a chain instead, where the safe lock takes
- * an intermediate lock (middle_class) where this lock is
- * not the same as the safe lock, then the lock chain is
- * used to describe the problem. Otherwise we would need
- * to show a different CPU case for each link in the chain
- * from the safe_class lock to the unsafe_class lock.
- */
- if (middle_class != unsafe_class) {
- printk("Chain exists of:\n ");
- __print_lock_name(safe_class);
- printk(KERN_CONT " --> ");
- __print_lock_name(middle_class);
- printk(KERN_CONT " --> ");
- __print_lock_name(unsafe_class);
- printk(KERN_CONT "\n\n");
- }
- printk(" Possible interrupt unsafe locking scenario:\n\n");
- printk(" CPU0 CPU1\n");
- printk(" ---- ----\n");
- printk(" lock(");
- __print_lock_name(unsafe_class);
- printk(KERN_CONT ");\n");
- printk(" local_irq_disable();\n");
- printk(" lock(");
- __print_lock_name(safe_class);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(middle_class);
- printk(KERN_CONT ");\n");
- printk(" <Interrupt>\n");
- printk(" lock(");
- __print_lock_name(safe_class);
- printk(KERN_CONT ");\n");
- printk("\n *** DEADLOCK ***\n\n");
- }
- static void
- print_bad_irq_dependency(struct task_struct *curr,
- struct lock_list *prev_root,
- struct lock_list *next_root,
- struct lock_list *backwards_entry,
- struct lock_list *forwards_entry,
- struct held_lock *prev,
- struct held_lock *next,
- enum lock_usage_bit bit1,
- enum lock_usage_bit bit2,
- const char *irqclass)
- {
- if (!debug_locks_off_graph_unlock() || debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("=====================================================\n");
- pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
- irqclass, irqclass);
- print_kernel_ident();
- pr_warn("-----------------------------------------------------\n");
- pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
- curr->comm, task_pid_nr(curr),
- lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
- curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
- lockdep_hardirqs_enabled(),
- curr->softirqs_enabled);
- print_lock(next);
- pr_warn("\nand this task is already holding:\n");
- print_lock(prev);
- pr_warn("which would create a new lock dependency:\n");
- print_lock_name(hlock_class(prev));
- pr_cont(" ->");
- print_lock_name(hlock_class(next));
- pr_cont("\n");
- pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
- irqclass);
- print_lock_name(backwards_entry->class);
- pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
- print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
- pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
- print_lock_name(forwards_entry->class);
- pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
- pr_warn("...");
- print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
- pr_warn("\nother info that might help us debug this:\n\n");
- print_irq_lock_scenario(backwards_entry, forwards_entry,
- hlock_class(prev), hlock_class(next));
- lockdep_print_held_locks(curr);
- pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
- print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
- pr_warn("\nthe dependencies between the lock to be acquired");
- pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
- next_root->trace = save_trace();
- if (!next_root->trace)
- return;
- print_shortest_lock_dependencies(forwards_entry, next_root);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- static const char *state_names[] = {
- #define LOCKDEP_STATE(__STATE) \
- __stringify(__STATE),
- #include "lockdep_states.h"
- #undef LOCKDEP_STATE
- };
- static const char *state_rnames[] = {
- #define LOCKDEP_STATE(__STATE) \
- __stringify(__STATE)"-READ",
- #include "lockdep_states.h"
- #undef LOCKDEP_STATE
- };
- static inline const char *state_name(enum lock_usage_bit bit)
- {
- if (bit & LOCK_USAGE_READ_MASK)
- return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
- else
- return state_names[bit >> LOCK_USAGE_DIR_MASK];
- }
- /*
- * The bit number is encoded like:
- *
- * bit0: 0 exclusive, 1 read lock
- * bit1: 0 used in irq, 1 irq enabled
- * bit2-n: state
- */
- static int exclusive_bit(int new_bit)
- {
- int state = new_bit & LOCK_USAGE_STATE_MASK;
- int dir = new_bit & LOCK_USAGE_DIR_MASK;
- /*
- * keep state, bit flip the direction and strip read.
- */
- return state | (dir ^ LOCK_USAGE_DIR_MASK);
- }
- /*
- * Observe that when given a bitmask where each bitnr is encoded as above, a
- * right shift of the mask transforms the individual bitnrs as -1 and
- * conversely, a left shift transforms into +1 for the individual bitnrs.
- *
- * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
- * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
- * instead by subtracting the bit number by 2, or shifting the mask right by 2.
- *
- * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
- *
- * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
- * all bits set) and recompose with bitnr1 flipped.
- */
- static unsigned long invert_dir_mask(unsigned long mask)
- {
- unsigned long excl = 0;
- /* Invert dir */
- excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
- excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
- return excl;
- }
- /*
- * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
- * usage may cause deadlock too, for example:
- *
- * P1 P2
- * <irq disabled>
- * write_lock(l1); <irq enabled>
- * read_lock(l2);
- * write_lock(l2);
- * <in irq>
- * read_lock(l1);
- *
- * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
- * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
- * deadlock.
- *
- * In fact, all of the following cases may cause deadlocks:
- *
- * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
- * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
- * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
- * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
- *
- * As a result, to calculate the "exclusive mask", first we invert the
- * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
- * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
- * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
- */
- static unsigned long exclusive_mask(unsigned long mask)
- {
- unsigned long excl = invert_dir_mask(mask);
- excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
- excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
- return excl;
- }
- /*
- * Retrieve the _possible_ original mask to which @mask is
- * exclusive. Ie: this is the opposite of exclusive_mask().
- * Note that 2 possible original bits can match an exclusive
- * bit: one has LOCK_USAGE_READ_MASK set, the other has it
- * cleared. So both are returned for each exclusive bit.
- */
- static unsigned long original_mask(unsigned long mask)
- {
- unsigned long excl = invert_dir_mask(mask);
- /* Include read in existing usages */
- excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
- excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
- return excl;
- }
- /*
- * Find the first pair of bit match between an original
- * usage mask and an exclusive usage mask.
- */
- static int find_exclusive_match(unsigned long mask,
- unsigned long excl_mask,
- enum lock_usage_bit *bitp,
- enum lock_usage_bit *excl_bitp)
- {
- int bit, excl, excl_read;
- for_each_set_bit(bit, &mask, LOCK_USED) {
- /*
- * exclusive_bit() strips the read bit, however,
- * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
- * to search excl | LOCK_USAGE_READ_MASK as well.
- */
- excl = exclusive_bit(bit);
- excl_read = excl | LOCK_USAGE_READ_MASK;
- if (excl_mask & lock_flag(excl)) {
- *bitp = bit;
- *excl_bitp = excl;
- return 0;
- } else if (excl_mask & lock_flag(excl_read)) {
- *bitp = bit;
- *excl_bitp = excl_read;
- return 0;
- }
- }
- return -1;
- }
- /*
- * Prove that the new dependency does not connect a hardirq-safe(-read)
- * lock with a hardirq-unsafe lock - to achieve this we search
- * the backwards-subgraph starting at <prev>, and the
- * forwards-subgraph starting at <next>:
- */
- static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
- struct held_lock *next)
- {
- unsigned long usage_mask = 0, forward_mask, backward_mask;
- enum lock_usage_bit forward_bit = 0, backward_bit = 0;
- struct lock_list *target_entry1;
- struct lock_list *target_entry;
- struct lock_list this, that;
- enum bfs_result ret;
- /*
- * Step 1: gather all hard/soft IRQs usages backward in an
- * accumulated usage mask.
- */
- bfs_init_rootb(&this, prev);
- ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
- if (bfs_error(ret)) {
- print_bfs_bug(ret);
- return 0;
- }
- usage_mask &= LOCKF_USED_IN_IRQ_ALL;
- if (!usage_mask)
- return 1;
- /*
- * Step 2: find exclusive uses forward that match the previous
- * backward accumulated mask.
- */
- forward_mask = exclusive_mask(usage_mask);
- bfs_init_root(&that, next);
- ret = find_usage_forwards(&that, forward_mask, &target_entry1);
- if (bfs_error(ret)) {
- print_bfs_bug(ret);
- return 0;
- }
- if (ret == BFS_RNOMATCH)
- return 1;
- /*
- * Step 3: we found a bad match! Now retrieve a lock from the backward
- * list whose usage mask matches the exclusive usage mask from the
- * lock found on the forward list.
- *
- * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
- * the follow case:
- *
- * When trying to add A -> B to the graph, we find that there is a
- * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
- * that B -> ... -> M. However M is **softirq-safe**, if we use exact
- * invert bits of M's usage_mask, we will find another lock N that is
- * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
- * cause a inversion deadlock.
- */
- backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
- ret = find_usage_backwards(&this, backward_mask, &target_entry);
- if (bfs_error(ret)) {
- print_bfs_bug(ret);
- return 0;
- }
- if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
- return 1;
- /*
- * Step 4: narrow down to a pair of incompatible usage bits
- * and report it.
- */
- ret = find_exclusive_match(target_entry->class->usage_mask,
- target_entry1->class->usage_mask,
- &backward_bit, &forward_bit);
- if (DEBUG_LOCKS_WARN_ON(ret == -1))
- return 1;
- print_bad_irq_dependency(curr, &this, &that,
- target_entry, target_entry1,
- prev, next,
- backward_bit, forward_bit,
- state_name(backward_bit));
- return 0;
- }
- #else
- static inline int check_irq_usage(struct task_struct *curr,
- struct held_lock *prev, struct held_lock *next)
- {
- return 1;
- }
- static inline bool usage_skip(struct lock_list *entry, void *mask)
- {
- return false;
- }
- #endif /* CONFIG_TRACE_IRQFLAGS */
- #ifdef CONFIG_LOCKDEP_SMALL
- /*
- * Check that the dependency graph starting at <src> can lead to
- * <target> or not. If it can, <src> -> <target> dependency is already
- * in the graph.
- *
- * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if
- * any error appears in the bfs search.
- */
- static noinline enum bfs_result
- check_redundant(struct held_lock *src, struct held_lock *target)
- {
- enum bfs_result ret;
- struct lock_list *target_entry;
- struct lock_list src_entry;
- bfs_init_root(&src_entry, src);
- /*
- * Special setup for check_redundant().
- *
- * To report redundant, we need to find a strong dependency path that
- * is equal to or stronger than <src> -> <target>. So if <src> is E,
- * we need to let __bfs() only search for a path starting at a -(E*)->,
- * we achieve this by setting the initial node's ->only_xr to true in
- * that case. And if <prev> is S, we set initial ->only_xr to false
- * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
- */
- src_entry.only_xr = src->read == 0;
- debug_atomic_inc(nr_redundant_checks);
- /*
- * Note: we skip local_lock() for redundant check, because as the
- * comment in usage_skip(), A -> local_lock() -> B and A -> B are not
- * the same.
- */
- ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
- if (ret == BFS_RMATCH)
- debug_atomic_inc(nr_redundant);
- return ret;
- }
- #else
- static inline enum bfs_result
- check_redundant(struct held_lock *src, struct held_lock *target)
- {
- return BFS_RNOMATCH;
- }
- #endif
- static void inc_chains(int irq_context)
- {
- if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
- nr_hardirq_chains++;
- else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
- nr_softirq_chains++;
- else
- nr_process_chains++;
- }
- static void dec_chains(int irq_context)
- {
- if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
- nr_hardirq_chains--;
- else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
- nr_softirq_chains--;
- else
- nr_process_chains--;
- }
- static void
- print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
- {
- struct lock_class *next = hlock_class(nxt);
- struct lock_class *prev = hlock_class(prv);
- printk(" Possible unsafe locking scenario:\n\n");
- printk(" CPU0\n");
- printk(" ----\n");
- printk(" lock(");
- __print_lock_name(prev);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(next);
- printk(KERN_CONT ");\n");
- printk("\n *** DEADLOCK ***\n\n");
- printk(" May be due to missing lock nesting notation\n\n");
- }
- static void
- print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
- struct held_lock *next)
- {
- if (!debug_locks_off_graph_unlock() || debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("============================================\n");
- pr_warn("WARNING: possible recursive locking detected\n");
- print_kernel_ident();
- pr_warn("--------------------------------------------\n");
- pr_warn("%s/%d is trying to acquire lock:\n",
- curr->comm, task_pid_nr(curr));
- print_lock(next);
- pr_warn("\nbut task is already holding lock:\n");
- print_lock(prev);
- pr_warn("\nother info that might help us debug this:\n");
- print_deadlock_scenario(next, prev);
- lockdep_print_held_locks(curr);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- /*
- * Check whether we are holding such a class already.
- *
- * (Note that this has to be done separately, because the graph cannot
- * detect such classes of deadlocks.)
- *
- * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
- * lock class is held but nest_lock is also held, i.e. we rely on the
- * nest_lock to avoid the deadlock.
- */
- static int
- check_deadlock(struct task_struct *curr, struct held_lock *next)
- {
- struct held_lock *prev;
- struct held_lock *nest = NULL;
- int i;
- for (i = 0; i < curr->lockdep_depth; i++) {
- prev = curr->held_locks + i;
- if (prev->instance == next->nest_lock)
- nest = prev;
- if (hlock_class(prev) != hlock_class(next))
- continue;
- /*
- * Allow read-after-read recursion of the same
- * lock class (i.e. read_lock(lock)+read_lock(lock)):
- */
- if ((next->read == 2) && prev->read)
- continue;
- /*
- * We're holding the nest_lock, which serializes this lock's
- * nesting behaviour.
- */
- if (nest)
- return 2;
- print_deadlock_bug(curr, prev, next);
- return 0;
- }
- return 1;
- }
- /*
- * There was a chain-cache miss, and we are about to add a new dependency
- * to a previous lock. We validate the following rules:
- *
- * - would the adding of the <prev> -> <next> dependency create a
- * circular dependency in the graph? [== circular deadlock]
- *
- * - does the new prev->next dependency connect any hardirq-safe lock
- * (in the full backwards-subgraph starting at <prev>) with any
- * hardirq-unsafe lock (in the full forwards-subgraph starting at
- * <next>)? [== illegal lock inversion with hardirq contexts]
- *
- * - does the new prev->next dependency connect any softirq-safe lock
- * (in the full backwards-subgraph starting at <prev>) with any
- * softirq-unsafe lock (in the full forwards-subgraph starting at
- * <next>)? [== illegal lock inversion with softirq contexts]
- *
- * any of these scenarios could lead to a deadlock.
- *
- * Then if all the validations pass, we add the forwards and backwards
- * dependency.
- */
- static int
- check_prev_add(struct task_struct *curr, struct held_lock *prev,
- struct held_lock *next, u16 distance,
- struct lock_trace **const trace)
- {
- struct lock_list *entry;
- enum bfs_result ret;
- if (!hlock_class(prev)->key || !hlock_class(next)->key) {
- /*
- * The warning statements below may trigger a use-after-free
- * of the class name. It is better to trigger a use-after free
- * and to have the class name most of the time instead of not
- * having the class name available.
- */
- WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
- "Detected use-after-free of lock class %px/%s\n",
- hlock_class(prev),
- hlock_class(prev)->name);
- WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
- "Detected use-after-free of lock class %px/%s\n",
- hlock_class(next),
- hlock_class(next)->name);
- return 2;
- }
- /*
- * Prove that the new <prev> -> <next> dependency would not
- * create a circular dependency in the graph. (We do this by
- * a breadth-first search into the graph starting at <next>,
- * and check whether we can reach <prev>.)
- *
- * The search is limited by the size of the circular queue (i.e.,
- * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
- * in the graph whose neighbours are to be checked.
- */
- ret = check_noncircular(next, prev, trace);
- if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
- return 0;
- if (!check_irq_usage(curr, prev, next))
- return 0;
- /*
- * Is the <prev> -> <next> dependency already present?
- *
- * (this may occur even though this is a new chain: consider
- * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
- * chains - the second one will be new, but L1 already has
- * L2 added to its dependency list, due to the first chain.)
- */
- list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
- if (entry->class == hlock_class(next)) {
- if (distance == 1)
- entry->distance = 1;
- entry->dep |= calc_dep(prev, next);
- /*
- * Also, update the reverse dependency in @next's
- * ->locks_before list.
- *
- * Here we reuse @entry as the cursor, which is fine
- * because we won't go to the next iteration of the
- * outer loop:
- *
- * For normal cases, we return in the inner loop.
- *
- * If we fail to return, we have inconsistency, i.e.
- * <prev>::locks_after contains <next> while
- * <next>::locks_before doesn't contain <prev>. In
- * that case, we return after the inner and indicate
- * something is wrong.
- */
- list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
- if (entry->class == hlock_class(prev)) {
- if (distance == 1)
- entry->distance = 1;
- entry->dep |= calc_depb(prev, next);
- return 1;
- }
- }
- /* <prev> is not found in <next>::locks_before */
- return 0;
- }
- }
- /*
- * Is the <prev> -> <next> link redundant?
- */
- ret = check_redundant(prev, next);
- if (bfs_error(ret))
- return 0;
- else if (ret == BFS_RMATCH)
- return 2;
- if (!*trace) {
- *trace = save_trace();
- if (!*trace)
- return 0;
- }
- /*
- * Ok, all validations passed, add the new lock
- * to the previous lock's dependency list:
- */
- ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
- &hlock_class(prev)->locks_after, distance,
- calc_dep(prev, next), *trace);
- if (!ret)
- return 0;
- ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
- &hlock_class(next)->locks_before, distance,
- calc_depb(prev, next), *trace);
- if (!ret)
- return 0;
- return 2;
- }
- /*
- * Add the dependency to all directly-previous locks that are 'relevant'.
- * The ones that are relevant are (in increasing distance from curr):
- * all consecutive trylock entries and the final non-trylock entry - or
- * the end of this context's lock-chain - whichever comes first.
- */
- static int
- check_prevs_add(struct task_struct *curr, struct held_lock *next)
- {
- struct lock_trace *trace = NULL;
- int depth = curr->lockdep_depth;
- struct held_lock *hlock;
- /*
- * Debugging checks.
- *
- * Depth must not be zero for a non-head lock:
- */
- if (!depth)
- goto out_bug;
- /*
- * At least two relevant locks must exist for this
- * to be a head:
- */
- if (curr->held_locks[depth].irq_context !=
- curr->held_locks[depth-1].irq_context)
- goto out_bug;
- for (;;) {
- u16 distance = curr->lockdep_depth - depth + 1;
- hlock = curr->held_locks + depth - 1;
- if (hlock->check) {
- int ret = check_prev_add(curr, hlock, next, distance, &trace);
- if (!ret)
- return 0;
- /*
- * Stop after the first non-trylock entry,
- * as non-trylock entries have added their
- * own direct dependencies already, so this
- * lock is connected to them indirectly:
- */
- if (!hlock->trylock)
- break;
- }
- depth--;
- /*
- * End of lock-stack?
- */
- if (!depth)
- break;
- /*
- * Stop the search if we cross into another context:
- */
- if (curr->held_locks[depth].irq_context !=
- curr->held_locks[depth-1].irq_context)
- break;
- }
- return 1;
- out_bug:
- if (!debug_locks_off_graph_unlock())
- return 0;
- /*
- * Clearly we all shouldn't be here, but since we made it we
- * can reliable say we messed up our state. See the above two
- * gotos for reasons why we could possibly end up here.
- */
- WARN_ON(1);
- return 0;
- }
- struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
- static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
- static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
- unsigned long nr_zapped_lock_chains;
- unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
- unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
- unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
- /*
- * The first 2 chain_hlocks entries in the chain block in the bucket
- * list contains the following meta data:
- *
- * entry[0]:
- * Bit 15 - always set to 1 (it is not a class index)
- * Bits 0-14 - upper 15 bits of the next block index
- * entry[1] - lower 16 bits of next block index
- *
- * A next block index of all 1 bits means it is the end of the list.
- *
- * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
- * the chain block size:
- *
- * entry[2] - upper 16 bits of the chain block size
- * entry[3] - lower 16 bits of the chain block size
- */
- #define MAX_CHAIN_BUCKETS 16
- #define CHAIN_BLK_FLAG (1U << 15)
- #define CHAIN_BLK_LIST_END 0xFFFFU
- static int chain_block_buckets[MAX_CHAIN_BUCKETS];
- static inline int size_to_bucket(int size)
- {
- if (size > MAX_CHAIN_BUCKETS)
- return 0;
- return size - 1;
- }
- /*
- * Iterate all the chain blocks in a bucket.
- */
- #define for_each_chain_block(bucket, prev, curr) \
- for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
- (curr) >= 0; \
- (prev) = (curr), (curr) = chain_block_next(curr))
- /*
- * next block or -1
- */
- static inline int chain_block_next(int offset)
- {
- int next = chain_hlocks[offset];
- WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
- if (next == CHAIN_BLK_LIST_END)
- return -1;
- next &= ~CHAIN_BLK_FLAG;
- next <<= 16;
- next |= chain_hlocks[offset + 1];
- return next;
- }
- /*
- * bucket-0 only
- */
- static inline int chain_block_size(int offset)
- {
- return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
- }
- static inline void init_chain_block(int offset, int next, int bucket, int size)
- {
- chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
- chain_hlocks[offset + 1] = (u16)next;
- if (size && !bucket) {
- chain_hlocks[offset + 2] = size >> 16;
- chain_hlocks[offset + 3] = (u16)size;
- }
- }
- static inline void add_chain_block(int offset, int size)
- {
- int bucket = size_to_bucket(size);
- int next = chain_block_buckets[bucket];
- int prev, curr;
- if (unlikely(size < 2)) {
- /*
- * We can't store single entries on the freelist. Leak them.
- *
- * One possible way out would be to uniquely mark them, other
- * than with CHAIN_BLK_FLAG, such that we can recover them when
- * the block before it is re-added.
- */
- if (size)
- nr_lost_chain_hlocks++;
- return;
- }
- nr_free_chain_hlocks += size;
- if (!bucket) {
- nr_large_chain_blocks++;
- /*
- * Variable sized, sort large to small.
- */
- for_each_chain_block(0, prev, curr) {
- if (size >= chain_block_size(curr))
- break;
- }
- init_chain_block(offset, curr, 0, size);
- if (prev < 0)
- chain_block_buckets[0] = offset;
- else
- init_chain_block(prev, offset, 0, 0);
- return;
- }
- /*
- * Fixed size, add to head.
- */
- init_chain_block(offset, next, bucket, size);
- chain_block_buckets[bucket] = offset;
- }
- /*
- * Only the first block in the list can be deleted.
- *
- * For the variable size bucket[0], the first block (the largest one) is
- * returned, broken up and put back into the pool. So if a chain block of
- * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
- * queued up after the primordial chain block and never be used until the
- * hlock entries in the primordial chain block is almost used up. That
- * causes fragmentation and reduce allocation efficiency. That can be
- * monitored by looking at the "large chain blocks" number in lockdep_stats.
- */
- static inline void del_chain_block(int bucket, int size, int next)
- {
- nr_free_chain_hlocks -= size;
- chain_block_buckets[bucket] = next;
- if (!bucket)
- nr_large_chain_blocks--;
- }
- static void init_chain_block_buckets(void)
- {
- int i;
- for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
- chain_block_buckets[i] = -1;
- add_chain_block(0, ARRAY_SIZE(chain_hlocks));
- }
- /*
- * Return offset of a chain block of the right size or -1 if not found.
- *
- * Fairly simple worst-fit allocator with the addition of a number of size
- * specific free lists.
- */
- static int alloc_chain_hlocks(int req)
- {
- int bucket, curr, size;
- /*
- * We rely on the MSB to act as an escape bit to denote freelist
- * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
- */
- BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
- init_data_structures_once();
- if (nr_free_chain_hlocks < req)
- return -1;
- /*
- * We require a minimum of 2 (u16) entries to encode a freelist
- * 'pointer'.
- */
- req = max(req, 2);
- bucket = size_to_bucket(req);
- curr = chain_block_buckets[bucket];
- if (bucket) {
- if (curr >= 0) {
- del_chain_block(bucket, req, chain_block_next(curr));
- return curr;
- }
- /* Try bucket 0 */
- curr = chain_block_buckets[0];
- }
- /*
- * The variable sized freelist is sorted by size; the first entry is
- * the largest. Use it if it fits.
- */
- if (curr >= 0) {
- size = chain_block_size(curr);
- if (likely(size >= req)) {
- del_chain_block(0, size, chain_block_next(curr));
- if (size > req)
- add_chain_block(curr + req, size - req);
- return curr;
- }
- }
- /*
- * Last resort, split a block in a larger sized bucket.
- */
- for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
- bucket = size_to_bucket(size);
- curr = chain_block_buckets[bucket];
- if (curr < 0)
- continue;
- del_chain_block(bucket, size, chain_block_next(curr));
- add_chain_block(curr + req, size - req);
- return curr;
- }
- return -1;
- }
- static inline void free_chain_hlocks(int base, int size)
- {
- add_chain_block(base, max(size, 2));
- }
- struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
- {
- u16 chain_hlock = chain_hlocks[chain->base + i];
- unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
- return lock_classes + class_idx;
- }
- /*
- * Returns the index of the first held_lock of the current chain
- */
- static inline int get_first_held_lock(struct task_struct *curr,
- struct held_lock *hlock)
- {
- int i;
- struct held_lock *hlock_curr;
- for (i = curr->lockdep_depth - 1; i >= 0; i--) {
- hlock_curr = curr->held_locks + i;
- if (hlock_curr->irq_context != hlock->irq_context)
- break;
- }
- return ++i;
- }
- #ifdef CONFIG_DEBUG_LOCKDEP
- /*
- * Returns the next chain_key iteration
- */
- static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
- {
- u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
- printk(" hlock_id:%d -> chain_key:%016Lx",
- (unsigned int)hlock_id,
- (unsigned long long)new_chain_key);
- return new_chain_key;
- }
- static void
- print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
- {
- struct held_lock *hlock;
- u64 chain_key = INITIAL_CHAIN_KEY;
- int depth = curr->lockdep_depth;
- int i = get_first_held_lock(curr, hlock_next);
- printk("depth: %u (irq_context %u)\n", depth - i + 1,
- hlock_next->irq_context);
- for (; i < depth; i++) {
- hlock = curr->held_locks + i;
- chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
- print_lock(hlock);
- }
- print_chain_key_iteration(hlock_id(hlock_next), chain_key);
- print_lock(hlock_next);
- }
- static void print_chain_keys_chain(struct lock_chain *chain)
- {
- int i;
- u64 chain_key = INITIAL_CHAIN_KEY;
- u16 hlock_id;
- printk("depth: %u\n", chain->depth);
- for (i = 0; i < chain->depth; i++) {
- hlock_id = chain_hlocks[chain->base + i];
- chain_key = print_chain_key_iteration(hlock_id, chain_key);
- print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
- printk("\n");
- }
- }
- static void print_collision(struct task_struct *curr,
- struct held_lock *hlock_next,
- struct lock_chain *chain)
- {
- pr_warn("\n");
- pr_warn("============================\n");
- pr_warn("WARNING: chain_key collision\n");
- print_kernel_ident();
- pr_warn("----------------------------\n");
- pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
- pr_warn("Hash chain already cached but the contents don't match!\n");
- pr_warn("Held locks:");
- print_chain_keys_held_locks(curr, hlock_next);
- pr_warn("Locks in cached chain:");
- print_chain_keys_chain(chain);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- #endif
- /*
- * Checks whether the chain and the current held locks are consistent
- * in depth and also in content. If they are not it most likely means
- * that there was a collision during the calculation of the chain_key.
- * Returns: 0 not passed, 1 passed
- */
- static int check_no_collision(struct task_struct *curr,
- struct held_lock *hlock,
- struct lock_chain *chain)
- {
- #ifdef CONFIG_DEBUG_LOCKDEP
- int i, j, id;
- i = get_first_held_lock(curr, hlock);
- if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
- print_collision(curr, hlock, chain);
- return 0;
- }
- for (j = 0; j < chain->depth - 1; j++, i++) {
- id = hlock_id(&curr->held_locks[i]);
- if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
- print_collision(curr, hlock, chain);
- return 0;
- }
- }
- #endif
- return 1;
- }
- /*
- * Given an index that is >= -1, return the index of the next lock chain.
- * Return -2 if there is no next lock chain.
- */
- long lockdep_next_lockchain(long i)
- {
- i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
- return i < ARRAY_SIZE(lock_chains) ? i : -2;
- }
- unsigned long lock_chain_count(void)
- {
- return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
- }
- /* Must be called with the graph lock held. */
- static struct lock_chain *alloc_lock_chain(void)
- {
- int idx = find_first_zero_bit(lock_chains_in_use,
- ARRAY_SIZE(lock_chains));
- if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
- return NULL;
- __set_bit(idx, lock_chains_in_use);
- return lock_chains + idx;
- }
- /*
- * Adds a dependency chain into chain hashtable. And must be called with
- * graph_lock held.
- *
- * Return 0 if fail, and graph_lock is released.
- * Return 1 if succeed, with graph_lock held.
- */
- static inline int add_chain_cache(struct task_struct *curr,
- struct held_lock *hlock,
- u64 chain_key)
- {
- struct hlist_head *hash_head = chainhashentry(chain_key);
- struct lock_chain *chain;
- int i, j;
- /*
- * The caller must hold the graph lock, ensure we've got IRQs
- * disabled to make this an IRQ-safe lock.. for recursion reasons
- * lockdep won't complain about its own locking errors.
- */
- if (lockdep_assert_locked())
- return 0;
- chain = alloc_lock_chain();
- if (!chain) {
- if (!debug_locks_off_graph_unlock())
- return 0;
- print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
- dump_stack();
- return 0;
- }
- chain->chain_key = chain_key;
- chain->irq_context = hlock->irq_context;
- i = get_first_held_lock(curr, hlock);
- chain->depth = curr->lockdep_depth + 1 - i;
- BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
- BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
- BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
- j = alloc_chain_hlocks(chain->depth);
- if (j < 0) {
- if (!debug_locks_off_graph_unlock())
- return 0;
- print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
- dump_stack();
- return 0;
- }
- chain->base = j;
- for (j = 0; j < chain->depth - 1; j++, i++) {
- int lock_id = hlock_id(curr->held_locks + i);
- chain_hlocks[chain->base + j] = lock_id;
- }
- chain_hlocks[chain->base + j] = hlock_id(hlock);
- hlist_add_head_rcu(&chain->entry, hash_head);
- debug_atomic_inc(chain_lookup_misses);
- inc_chains(chain->irq_context);
- return 1;
- }
- /*
- * Look up a dependency chain. Must be called with either the graph lock or
- * the RCU read lock held.
- */
- static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
- {
- struct hlist_head *hash_head = chainhashentry(chain_key);
- struct lock_chain *chain;
- hlist_for_each_entry_rcu(chain, hash_head, entry) {
- if (READ_ONCE(chain->chain_key) == chain_key) {
- debug_atomic_inc(chain_lookup_hits);
- return chain;
- }
- }
- return NULL;
- }
- /*
- * If the key is not present yet in dependency chain cache then
- * add it and return 1 - in this case the new dependency chain is
- * validated. If the key is already hashed, return 0.
- * (On return with 1 graph_lock is held.)
- */
- static inline int lookup_chain_cache_add(struct task_struct *curr,
- struct held_lock *hlock,
- u64 chain_key)
- {
- struct lock_class *class = hlock_class(hlock);
- struct lock_chain *chain = lookup_chain_cache(chain_key);
- if (chain) {
- cache_hit:
- if (!check_no_collision(curr, hlock, chain))
- return 0;
- if (very_verbose(class)) {
- printk("\nhash chain already cached, key: "
- "%016Lx tail class: [%px] %s\n",
- (unsigned long long)chain_key,
- class->key, class->name);
- }
- return 0;
- }
- if (very_verbose(class)) {
- printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
- (unsigned long long)chain_key, class->key, class->name);
- }
- if (!graph_lock())
- return 0;
- /*
- * We have to walk the chain again locked - to avoid duplicates:
- */
- chain = lookup_chain_cache(chain_key);
- if (chain) {
- graph_unlock();
- goto cache_hit;
- }
- if (!add_chain_cache(curr, hlock, chain_key))
- return 0;
- return 1;
- }
- static int validate_chain(struct task_struct *curr,
- struct held_lock *hlock,
- int chain_head, u64 chain_key)
- {
- /*
- * Trylock needs to maintain the stack of held locks, but it
- * does not add new dependencies, because trylock can be done
- * in any order.
- *
- * We look up the chain_key and do the O(N^2) check and update of
- * the dependencies only if this is a new dependency chain.
- * (If lookup_chain_cache_add() return with 1 it acquires
- * graph_lock for us)
- */
- if (!hlock->trylock && hlock->check &&
- lookup_chain_cache_add(curr, hlock, chain_key)) {
- /*
- * Check whether last held lock:
- *
- * - is irq-safe, if this lock is irq-unsafe
- * - is softirq-safe, if this lock is hardirq-unsafe
- *
- * And check whether the new lock's dependency graph
- * could lead back to the previous lock:
- *
- * - within the current held-lock stack
- * - across our accumulated lock dependency records
- *
- * any of these scenarios could lead to a deadlock.
- */
- /*
- * The simple case: does the current hold the same lock
- * already?
- */
- int ret = check_deadlock(curr, hlock);
- if (!ret)
- return 0;
- /*
- * Add dependency only if this lock is not the head
- * of the chain, and if the new lock introduces no more
- * lock dependency (because we already hold a lock with the
- * same lock class) nor deadlock (because the nest_lock
- * serializes nesting locks), see the comments for
- * check_deadlock().
- */
- if (!chain_head && ret != 2) {
- if (!check_prevs_add(curr, hlock))
- return 0;
- }
- graph_unlock();
- } else {
- /* after lookup_chain_cache_add(): */
- if (unlikely(!debug_locks))
- return 0;
- }
- return 1;
- }
- #else
- static inline int validate_chain(struct task_struct *curr,
- struct held_lock *hlock,
- int chain_head, u64 chain_key)
- {
- return 1;
- }
- static void init_chain_block_buckets(void) { }
- #endif /* CONFIG_PROVE_LOCKING */
- /*
- * We are building curr_chain_key incrementally, so double-check
- * it from scratch, to make sure that it's done correctly:
- */
- static void check_chain_key(struct task_struct *curr)
- {
- #ifdef CONFIG_DEBUG_LOCKDEP
- struct held_lock *hlock, *prev_hlock = NULL;
- unsigned int i;
- u64 chain_key = INITIAL_CHAIN_KEY;
- for (i = 0; i < curr->lockdep_depth; i++) {
- hlock = curr->held_locks + i;
- if (chain_key != hlock->prev_chain_key) {
- debug_locks_off();
- /*
- * We got mighty confused, our chain keys don't match
- * with what we expect, someone trample on our task state?
- */
- WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
- curr->lockdep_depth, i,
- (unsigned long long)chain_key,
- (unsigned long long)hlock->prev_chain_key);
- return;
- }
- /*
- * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
- * it registered lock class index?
- */
- if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
- return;
- if (prev_hlock && (prev_hlock->irq_context !=
- hlock->irq_context))
- chain_key = INITIAL_CHAIN_KEY;
- chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
- prev_hlock = hlock;
- }
- if (chain_key != curr->curr_chain_key) {
- debug_locks_off();
- /*
- * More smoking hash instead of calculating it, damn see these
- * numbers float.. I bet that a pink elephant stepped on my memory.
- */
- WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
- curr->lockdep_depth, i,
- (unsigned long long)chain_key,
- (unsigned long long)curr->curr_chain_key);
- }
- #endif
- }
- #ifdef CONFIG_PROVE_LOCKING
- static int mark_lock(struct task_struct *curr, struct held_lock *this,
- enum lock_usage_bit new_bit);
- static void print_usage_bug_scenario(struct held_lock *lock)
- {
- struct lock_class *class = hlock_class(lock);
- printk(" Possible unsafe locking scenario:\n\n");
- printk(" CPU0\n");
- printk(" ----\n");
- printk(" lock(");
- __print_lock_name(class);
- printk(KERN_CONT ");\n");
- printk(" <Interrupt>\n");
- printk(" lock(");
- __print_lock_name(class);
- printk(KERN_CONT ");\n");
- printk("\n *** DEADLOCK ***\n\n");
- }
- static void
- print_usage_bug(struct task_struct *curr, struct held_lock *this,
- enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
- {
- if (!debug_locks_off() || debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("================================\n");
- pr_warn("WARNING: inconsistent lock state\n");
- print_kernel_ident();
- pr_warn("--------------------------------\n");
- pr_warn("inconsistent {%s} -> {%s} usage.\n",
- usage_str[prev_bit], usage_str[new_bit]);
- pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
- curr->comm, task_pid_nr(curr),
- lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
- lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
- lockdep_hardirqs_enabled(),
- lockdep_softirqs_enabled(curr));
- print_lock(this);
- pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
- print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
- print_irqtrace_events(curr);
- pr_warn("\nother info that might help us debug this:\n");
- print_usage_bug_scenario(this);
- lockdep_print_held_locks(curr);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- /*
- * Print out an error if an invalid bit is set:
- */
- static inline int
- valid_state(struct task_struct *curr, struct held_lock *this,
- enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
- {
- if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
- graph_unlock();
- print_usage_bug(curr, this, bad_bit, new_bit);
- return 0;
- }
- return 1;
- }
- /*
- * print irq inversion bug:
- */
- static void
- print_irq_inversion_bug(struct task_struct *curr,
- struct lock_list *root, struct lock_list *other,
- struct held_lock *this, int forwards,
- const char *irqclass)
- {
- struct lock_list *entry = other;
- struct lock_list *middle = NULL;
- int depth;
- if (!debug_locks_off_graph_unlock() || debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("========================================================\n");
- pr_warn("WARNING: possible irq lock inversion dependency detected\n");
- print_kernel_ident();
- pr_warn("--------------------------------------------------------\n");
- pr_warn("%s/%d just changed the state of lock:\n",
- curr->comm, task_pid_nr(curr));
- print_lock(this);
- if (forwards)
- pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
- else
- pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
- print_lock_name(other->class);
- pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
- pr_warn("\nother info that might help us debug this:\n");
- /* Find a middle lock (if one exists) */
- depth = get_lock_depth(other);
- do {
- if (depth == 0 && (entry != root)) {
- pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
- break;
- }
- middle = entry;
- entry = get_lock_parent(entry);
- depth--;
- } while (entry && entry != root && (depth >= 0));
- if (forwards)
- print_irq_lock_scenario(root, other,
- middle ? middle->class : root->class, other->class);
- else
- print_irq_lock_scenario(other, root,
- middle ? middle->class : other->class, root->class);
- lockdep_print_held_locks(curr);
- pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
- root->trace = save_trace();
- if (!root->trace)
- return;
- print_shortest_lock_dependencies(other, root);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- /*
- * Prove that in the forwards-direction subgraph starting at <this>
- * there is no lock matching <mask>:
- */
- static int
- check_usage_forwards(struct task_struct *curr, struct held_lock *this,
- enum lock_usage_bit bit)
- {
- enum bfs_result ret;
- struct lock_list root;
- struct lock_list *target_entry;
- enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
- unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
- bfs_init_root(&root, this);
- ret = find_usage_forwards(&root, usage_mask, &target_entry);
- if (bfs_error(ret)) {
- print_bfs_bug(ret);
- return 0;
- }
- if (ret == BFS_RNOMATCH)
- return 1;
- /* Check whether write or read usage is the match */
- if (target_entry->class->usage_mask & lock_flag(bit)) {
- print_irq_inversion_bug(curr, &root, target_entry,
- this, 1, state_name(bit));
- } else {
- print_irq_inversion_bug(curr, &root, target_entry,
- this, 1, state_name(read_bit));
- }
- return 0;
- }
- /*
- * Prove that in the backwards-direction subgraph starting at <this>
- * there is no lock matching <mask>:
- */
- static int
- check_usage_backwards(struct task_struct *curr, struct held_lock *this,
- enum lock_usage_bit bit)
- {
- enum bfs_result ret;
- struct lock_list root;
- struct lock_list *target_entry;
- enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
- unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
- bfs_init_rootb(&root, this);
- ret = find_usage_backwards(&root, usage_mask, &target_entry);
- if (bfs_error(ret)) {
- print_bfs_bug(ret);
- return 0;
- }
- if (ret == BFS_RNOMATCH)
- return 1;
- /* Check whether write or read usage is the match */
- if (target_entry->class->usage_mask & lock_flag(bit)) {
- print_irq_inversion_bug(curr, &root, target_entry,
- this, 0, state_name(bit));
- } else {
- print_irq_inversion_bug(curr, &root, target_entry,
- this, 0, state_name(read_bit));
- }
- return 0;
- }
- void print_irqtrace_events(struct task_struct *curr)
- {
- const struct irqtrace_events *trace = &curr->irqtrace;
- printk("irq event stamp: %u\n", trace->irq_events);
- printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
- trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
- (void *)trace->hardirq_enable_ip);
- printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
- trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
- (void *)trace->hardirq_disable_ip);
- printk("softirqs last enabled at (%u): [<%px>] %pS\n",
- trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
- (void *)trace->softirq_enable_ip);
- printk("softirqs last disabled at (%u): [<%px>] %pS\n",
- trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
- (void *)trace->softirq_disable_ip);
- }
- static int HARDIRQ_verbose(struct lock_class *class)
- {
- #if HARDIRQ_VERBOSE
- return class_filter(class);
- #endif
- return 0;
- }
- static int SOFTIRQ_verbose(struct lock_class *class)
- {
- #if SOFTIRQ_VERBOSE
- return class_filter(class);
- #endif
- return 0;
- }
- static int (*state_verbose_f[])(struct lock_class *class) = {
- #define LOCKDEP_STATE(__STATE) \
- __STATE##_verbose,
- #include "lockdep_states.h"
- #undef LOCKDEP_STATE
- };
- static inline int state_verbose(enum lock_usage_bit bit,
- struct lock_class *class)
- {
- return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
- }
- typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
- enum lock_usage_bit bit, const char *name);
- static int
- mark_lock_irq(struct task_struct *curr, struct held_lock *this,
- enum lock_usage_bit new_bit)
- {
- int excl_bit = exclusive_bit(new_bit);
- int read = new_bit & LOCK_USAGE_READ_MASK;
- int dir = new_bit & LOCK_USAGE_DIR_MASK;
- /*
- * Validate that this particular lock does not have conflicting
- * usage states.
- */
- if (!valid_state(curr, this, new_bit, excl_bit))
- return 0;
- /*
- * Check for read in write conflicts
- */
- if (!read && !valid_state(curr, this, new_bit,
- excl_bit + LOCK_USAGE_READ_MASK))
- return 0;
- /*
- * Validate that the lock dependencies don't have conflicting usage
- * states.
- */
- if (dir) {
- /*
- * mark ENABLED has to look backwards -- to ensure no dependee
- * has USED_IN state, which, again, would allow recursion deadlocks.
- */
- if (!check_usage_backwards(curr, this, excl_bit))
- return 0;
- } else {
- /*
- * mark USED_IN has to look forwards -- to ensure no dependency
- * has ENABLED state, which would allow recursion deadlocks.
- */
- if (!check_usage_forwards(curr, this, excl_bit))
- return 0;
- }
- if (state_verbose(new_bit, hlock_class(this)))
- return 2;
- return 1;
- }
- /*
- * Mark all held locks with a usage bit:
- */
- static int
- mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
- {
- struct held_lock *hlock;
- int i;
- for (i = 0; i < curr->lockdep_depth; i++) {
- enum lock_usage_bit hlock_bit = base_bit;
- hlock = curr->held_locks + i;
- if (hlock->read)
- hlock_bit += LOCK_USAGE_READ_MASK;
- BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
- if (!hlock->check)
- continue;
- if (!mark_lock(curr, hlock, hlock_bit))
- return 0;
- }
- return 1;
- }
- /*
- * Hardirqs will be enabled:
- */
- static void __trace_hardirqs_on_caller(void)
- {
- struct task_struct *curr = current;
- /*
- * We are going to turn hardirqs on, so set the
- * usage bit for all held locks:
- */
- if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
- return;
- /*
- * If we have softirqs enabled, then set the usage
- * bit for all held locks. (disabled hardirqs prevented
- * this bit from being set before)
- */
- if (curr->softirqs_enabled)
- mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
- }
- /**
- * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
- *
- * Invoked before a possible transition to RCU idle from exit to user or
- * guest mode. This ensures that all RCU operations are done before RCU
- * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
- * invoked to set the final state.
- */
- void lockdep_hardirqs_on_prepare(void)
- {
- if (unlikely(!debug_locks))
- return;
- /*
- * NMIs do not (and cannot) track lock dependencies, nothing to do.
- */
- if (unlikely(in_nmi()))
- return;
- if (unlikely(this_cpu_read(lockdep_recursion)))
- return;
- if (unlikely(lockdep_hardirqs_enabled())) {
- /*
- * Neither irq nor preemption are disabled here
- * so this is racy by nature but losing one hit
- * in a stat is not a big deal.
- */
- __debug_atomic_inc(redundant_hardirqs_on);
- return;
- }
- /*
- * We're enabling irqs and according to our state above irqs weren't
- * already enabled, yet we find the hardware thinks they are in fact
- * enabled.. someone messed up their IRQ state tracing.
- */
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return;
- /*
- * See the fine text that goes along with this variable definition.
- */
- if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
- return;
- /*
- * Can't allow enabling interrupts while in an interrupt handler,
- * that's general bad form and such. Recursion, limited stack etc..
- */
- if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
- return;
- current->hardirq_chain_key = current->curr_chain_key;
- lockdep_recursion_inc();
- __trace_hardirqs_on_caller();
- lockdep_recursion_finish();
- }
- EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
- void noinstr lockdep_hardirqs_on(unsigned long ip)
- {
- struct irqtrace_events *trace = ¤t->irqtrace;
- if (unlikely(!debug_locks))
- return;
- /*
- * NMIs can happen in the middle of local_irq_{en,dis}able() where the
- * tracking state and hardware state are out of sync.
- *
- * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
- * and not rely on hardware state like normal interrupts.
- */
- if (unlikely(in_nmi())) {
- if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
- return;
- /*
- * Skip:
- * - recursion check, because NMI can hit lockdep;
- * - hardware state check, because above;
- * - chain_key check, see lockdep_hardirqs_on_prepare().
- */
- goto skip_checks;
- }
- if (unlikely(this_cpu_read(lockdep_recursion)))
- return;
- if (lockdep_hardirqs_enabled()) {
- /*
- * Neither irq nor preemption are disabled here
- * so this is racy by nature but losing one hit
- * in a stat is not a big deal.
- */
- __debug_atomic_inc(redundant_hardirqs_on);
- return;
- }
- /*
- * We're enabling irqs and according to our state above irqs weren't
- * already enabled, yet we find the hardware thinks they are in fact
- * enabled.. someone messed up their IRQ state tracing.
- */
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return;
- /*
- * Ensure the lock stack remained unchanged between
- * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
- */
- DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
- current->curr_chain_key);
- skip_checks:
- /* we'll do an OFF -> ON transition: */
- __this_cpu_write(hardirqs_enabled, 1);
- trace->hardirq_enable_ip = ip;
- trace->hardirq_enable_event = ++trace->irq_events;
- debug_atomic_inc(hardirqs_on_events);
- }
- EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
- /*
- * Hardirqs were disabled:
- */
- void noinstr lockdep_hardirqs_off(unsigned long ip)
- {
- if (unlikely(!debug_locks))
- return;
- /*
- * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
- * they will restore the software state. This ensures the software
- * state is consistent inside NMIs as well.
- */
- if (in_nmi()) {
- if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
- return;
- } else if (__this_cpu_read(lockdep_recursion))
- return;
- /*
- * So we're supposed to get called after you mask local IRQs, but for
- * some reason the hardware doesn't quite think you did a proper job.
- */
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return;
- if (lockdep_hardirqs_enabled()) {
- struct irqtrace_events *trace = ¤t->irqtrace;
- /*
- * We have done an ON -> OFF transition:
- */
- __this_cpu_write(hardirqs_enabled, 0);
- trace->hardirq_disable_ip = ip;
- trace->hardirq_disable_event = ++trace->irq_events;
- debug_atomic_inc(hardirqs_off_events);
- } else {
- debug_atomic_inc(redundant_hardirqs_off);
- }
- }
- EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
- /*
- * Softirqs will be enabled:
- */
- void lockdep_softirqs_on(unsigned long ip)
- {
- struct irqtrace_events *trace = ¤t->irqtrace;
- if (unlikely(!lockdep_enabled()))
- return;
- /*
- * We fancy IRQs being disabled here, see softirq.c, avoids
- * funny state and nesting things.
- */
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return;
- if (current->softirqs_enabled) {
- debug_atomic_inc(redundant_softirqs_on);
- return;
- }
- lockdep_recursion_inc();
- /*
- * We'll do an OFF -> ON transition:
- */
- current->softirqs_enabled = 1;
- trace->softirq_enable_ip = ip;
- trace->softirq_enable_event = ++trace->irq_events;
- debug_atomic_inc(softirqs_on_events);
- /*
- * We are going to turn softirqs on, so set the
- * usage bit for all held locks, if hardirqs are
- * enabled too:
- */
- if (lockdep_hardirqs_enabled())
- mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
- lockdep_recursion_finish();
- }
- /*
- * Softirqs were disabled:
- */
- void lockdep_softirqs_off(unsigned long ip)
- {
- if (unlikely(!lockdep_enabled()))
- return;
- /*
- * We fancy IRQs being disabled here, see softirq.c
- */
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return;
- if (current->softirqs_enabled) {
- struct irqtrace_events *trace = ¤t->irqtrace;
- /*
- * We have done an ON -> OFF transition:
- */
- current->softirqs_enabled = 0;
- trace->softirq_disable_ip = ip;
- trace->softirq_disable_event = ++trace->irq_events;
- debug_atomic_inc(softirqs_off_events);
- /*
- * Whoops, we wanted softirqs off, so why aren't they?
- */
- DEBUG_LOCKS_WARN_ON(!softirq_count());
- } else
- debug_atomic_inc(redundant_softirqs_off);
- }
- static int
- mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
- {
- if (!check)
- goto lock_used;
- /*
- * If non-trylock use in a hardirq or softirq context, then
- * mark the lock as used in these contexts:
- */
- if (!hlock->trylock) {
- if (hlock->read) {
- if (lockdep_hardirq_context())
- if (!mark_lock(curr, hlock,
- LOCK_USED_IN_HARDIRQ_READ))
- return 0;
- if (curr->softirq_context)
- if (!mark_lock(curr, hlock,
- LOCK_USED_IN_SOFTIRQ_READ))
- return 0;
- } else {
- if (lockdep_hardirq_context())
- if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
- return 0;
- if (curr->softirq_context)
- if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
- return 0;
- }
- }
- if (!hlock->hardirqs_off) {
- if (hlock->read) {
- if (!mark_lock(curr, hlock,
- LOCK_ENABLED_HARDIRQ_READ))
- return 0;
- if (curr->softirqs_enabled)
- if (!mark_lock(curr, hlock,
- LOCK_ENABLED_SOFTIRQ_READ))
- return 0;
- } else {
- if (!mark_lock(curr, hlock,
- LOCK_ENABLED_HARDIRQ))
- return 0;
- if (curr->softirqs_enabled)
- if (!mark_lock(curr, hlock,
- LOCK_ENABLED_SOFTIRQ))
- return 0;
- }
- }
- lock_used:
- /* mark it as used: */
- if (!mark_lock(curr, hlock, LOCK_USED))
- return 0;
- return 1;
- }
- static inline unsigned int task_irq_context(struct task_struct *task)
- {
- return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
- LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
- }
- static int separate_irq_context(struct task_struct *curr,
- struct held_lock *hlock)
- {
- unsigned int depth = curr->lockdep_depth;
- /*
- * Keep track of points where we cross into an interrupt context:
- */
- if (depth) {
- struct held_lock *prev_hlock;
- prev_hlock = curr->held_locks + depth-1;
- /*
- * If we cross into another context, reset the
- * hash key (this also prevents the checking and the
- * adding of the dependency to 'prev'):
- */
- if (prev_hlock->irq_context != hlock->irq_context)
- return 1;
- }
- return 0;
- }
- /*
- * Mark a lock with a usage bit, and validate the state transition:
- */
- static int mark_lock(struct task_struct *curr, struct held_lock *this,
- enum lock_usage_bit new_bit)
- {
- unsigned int new_mask, ret = 1;
- if (new_bit >= LOCK_USAGE_STATES) {
- DEBUG_LOCKS_WARN_ON(1);
- return 0;
- }
- if (new_bit == LOCK_USED && this->read)
- new_bit = LOCK_USED_READ;
- new_mask = 1 << new_bit;
- /*
- * If already set then do not dirty the cacheline,
- * nor do any checks:
- */
- if (likely(hlock_class(this)->usage_mask & new_mask))
- return 1;
- if (!graph_lock())
- return 0;
- /*
- * Make sure we didn't race:
- */
- if (unlikely(hlock_class(this)->usage_mask & new_mask))
- goto unlock;
- if (!hlock_class(this)->usage_mask)
- debug_atomic_dec(nr_unused_locks);
- hlock_class(this)->usage_mask |= new_mask;
- if (new_bit < LOCK_TRACE_STATES) {
- if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
- return 0;
- }
- if (new_bit < LOCK_USED) {
- ret = mark_lock_irq(curr, this, new_bit);
- if (!ret)
- return 0;
- }
- unlock:
- graph_unlock();
- /*
- * We must printk outside of the graph_lock:
- */
- if (ret == 2) {
- printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
- print_lock(this);
- print_irqtrace_events(curr);
- dump_stack();
- }
- return ret;
- }
- static inline short task_wait_context(struct task_struct *curr)
- {
- /*
- * Set appropriate wait type for the context; for IRQs we have to take
- * into account force_irqthread as that is implied by PREEMPT_RT.
- */
- if (lockdep_hardirq_context()) {
- /*
- * Check if force_irqthreads will run us threaded.
- */
- if (curr->hardirq_threaded || curr->irq_config)
- return LD_WAIT_CONFIG;
- return LD_WAIT_SPIN;
- } else if (curr->softirq_context) {
- /*
- * Softirqs are always threaded.
- */
- return LD_WAIT_CONFIG;
- }
- return LD_WAIT_MAX;
- }
- static int
- print_lock_invalid_wait_context(struct task_struct *curr,
- struct held_lock *hlock)
- {
- short curr_inner;
- if (!debug_locks_off())
- return 0;
- if (debug_locks_silent)
- return 0;
- pr_warn("\n");
- pr_warn("=============================\n");
- pr_warn("[ BUG: Invalid wait context ]\n");
- print_kernel_ident();
- pr_warn("-----------------------------\n");
- pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
- print_lock(hlock);
- pr_warn("other info that might help us debug this:\n");
- curr_inner = task_wait_context(curr);
- pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
- lockdep_print_held_locks(curr);
- pr_warn("stack backtrace:\n");
- dump_stack();
- return 0;
- }
- /*
- * Verify the wait_type context.
- *
- * This check validates we take locks in the right wait-type order; that is it
- * ensures that we do not take mutexes inside spinlocks and do not attempt to
- * acquire spinlocks inside raw_spinlocks and the sort.
- *
- * The entire thing is slightly more complex because of RCU, RCU is a lock that
- * can be taken from (pretty much) any context but also has constraints.
- * However when taken in a stricter environment the RCU lock does not loosen
- * the constraints.
- *
- * Therefore we must look for the strictest environment in the lock stack and
- * compare that to the lock we're trying to acquire.
- */
- static int check_wait_context(struct task_struct *curr, struct held_lock *next)
- {
- u8 next_inner = hlock_class(next)->wait_type_inner;
- u8 next_outer = hlock_class(next)->wait_type_outer;
- u8 curr_inner;
- int depth;
- if (!next_inner || next->trylock)
- return 0;
- if (!next_outer)
- next_outer = next_inner;
- /*
- * Find start of current irq_context..
- */
- for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
- struct held_lock *prev = curr->held_locks + depth;
- if (prev->irq_context != next->irq_context)
- break;
- }
- depth++;
- curr_inner = task_wait_context(curr);
- for (; depth < curr->lockdep_depth; depth++) {
- struct held_lock *prev = curr->held_locks + depth;
- u8 prev_inner = hlock_class(prev)->wait_type_inner;
- if (prev_inner) {
- /*
- * We can have a bigger inner than a previous one
- * when outer is smaller than inner, as with RCU.
- *
- * Also due to trylocks.
- */
- curr_inner = min(curr_inner, prev_inner);
- }
- }
- if (next_outer > curr_inner)
- return print_lock_invalid_wait_context(curr, next);
- return 0;
- }
- #else /* CONFIG_PROVE_LOCKING */
- static inline int
- mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
- {
- return 1;
- }
- static inline unsigned int task_irq_context(struct task_struct *task)
- {
- return 0;
- }
- static inline int separate_irq_context(struct task_struct *curr,
- struct held_lock *hlock)
- {
- return 0;
- }
- static inline int check_wait_context(struct task_struct *curr,
- struct held_lock *next)
- {
- return 0;
- }
- #endif /* CONFIG_PROVE_LOCKING */
- /*
- * Initialize a lock instance's lock-class mapping info:
- */
- void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
- struct lock_class_key *key, int subclass,
- u8 inner, u8 outer, u8 lock_type)
- {
- int i;
- for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
- lock->class_cache[i] = NULL;
- #ifdef CONFIG_LOCK_STAT
- lock->cpu = raw_smp_processor_id();
- #endif
- /*
- * Can't be having no nameless bastards around this place!
- */
- if (DEBUG_LOCKS_WARN_ON(!name)) {
- lock->name = "NULL";
- return;
- }
- lock->name = name;
- lock->wait_type_outer = outer;
- lock->wait_type_inner = inner;
- lock->lock_type = lock_type;
- /*
- * No key, no joy, we need to hash something.
- */
- if (DEBUG_LOCKS_WARN_ON(!key))
- return;
- /*
- * Sanity check, the lock-class key must either have been allocated
- * statically or must have been registered as a dynamic key.
- */
- if (!static_obj(key) && !is_dynamic_key(key)) {
- if (debug_locks)
- printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
- DEBUG_LOCKS_WARN_ON(1);
- return;
- }
- lock->key = key;
- if (unlikely(!debug_locks))
- return;
- if (subclass) {
- unsigned long flags;
- if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
- return;
- raw_local_irq_save(flags);
- lockdep_recursion_inc();
- register_lock_class(lock, subclass, 1);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- }
- EXPORT_SYMBOL_GPL(lockdep_init_map_type);
- struct lock_class_key __lockdep_no_validate__;
- EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
- static void
- print_lock_nested_lock_not_held(struct task_struct *curr,
- struct held_lock *hlock)
- {
- if (!debug_locks_off())
- return;
- if (debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("==================================\n");
- pr_warn("WARNING: Nested lock was not taken\n");
- print_kernel_ident();
- pr_warn("----------------------------------\n");
- pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
- print_lock(hlock);
- pr_warn("\nbut this task is not holding:\n");
- pr_warn("%s\n", hlock->nest_lock->name);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- pr_warn("\nother info that might help us debug this:\n");
- lockdep_print_held_locks(curr);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- static int __lock_is_held(const struct lockdep_map *lock, int read);
- /*
- * This gets called for every mutex_lock*()/spin_lock*() operation.
- * We maintain the dependency maps and validate the locking attempt:
- *
- * The callers must make sure that IRQs are disabled before calling it,
- * otherwise we could get an interrupt which would want to take locks,
- * which would end up in lockdep again.
- */
- static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
- int trylock, int read, int check, int hardirqs_off,
- struct lockdep_map *nest_lock, unsigned long ip,
- int references, int pin_count)
- {
- struct task_struct *curr = current;
- struct lock_class *class = NULL;
- struct held_lock *hlock;
- unsigned int depth;
- int chain_head = 0;
- int class_idx;
- u64 chain_key;
- if (unlikely(!debug_locks))
- return 0;
- if (!prove_locking || lock->key == &__lockdep_no_validate__)
- check = 0;
- if (subclass < NR_LOCKDEP_CACHING_CLASSES)
- class = lock->class_cache[subclass];
- /*
- * Not cached?
- */
- if (unlikely(!class)) {
- class = register_lock_class(lock, subclass, 0);
- if (!class)
- return 0;
- }
- debug_class_ops_inc(class);
- if (very_verbose(class)) {
- printk("\nacquire class [%px] %s", class->key, class->name);
- if (class->name_version > 1)
- printk(KERN_CONT "#%d", class->name_version);
- printk(KERN_CONT "\n");
- dump_stack();
- }
- /*
- * Add the lock to the list of currently held locks.
- * (we dont increase the depth just yet, up until the
- * dependency checks are done)
- */
- depth = curr->lockdep_depth;
- /*
- * Ran out of static storage for our per-task lock stack again have we?
- */
- if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
- return 0;
- class_idx = class - lock_classes;
- if (depth) { /* we're holding locks */
- hlock = curr->held_locks + depth - 1;
- if (hlock->class_idx == class_idx && nest_lock) {
- if (!references)
- references++;
- if (!hlock->references)
- hlock->references++;
- hlock->references += references;
- /* Overflow */
- if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
- return 0;
- return 2;
- }
- }
- hlock = curr->held_locks + depth;
- /*
- * Plain impossible, we just registered it and checked it weren't no
- * NULL like.. I bet this mushroom I ate was good!
- */
- if (DEBUG_LOCKS_WARN_ON(!class))
- return 0;
- hlock->class_idx = class_idx;
- hlock->acquire_ip = ip;
- hlock->instance = lock;
- hlock->nest_lock = nest_lock;
- hlock->irq_context = task_irq_context(curr);
- hlock->trylock = trylock;
- hlock->read = read;
- hlock->check = check;
- hlock->hardirqs_off = !!hardirqs_off;
- hlock->references = references;
- #ifdef CONFIG_LOCK_STAT
- hlock->waittime_stamp = 0;
- hlock->holdtime_stamp = lockstat_clock();
- #endif
- hlock->pin_count = pin_count;
- if (check_wait_context(curr, hlock))
- return 0;
- /* Initialize the lock usage bit */
- if (!mark_usage(curr, hlock, check))
- return 0;
- /*
- * Calculate the chain hash: it's the combined hash of all the
- * lock keys along the dependency chain. We save the hash value
- * at every step so that we can get the current hash easily
- * after unlock. The chain hash is then used to cache dependency
- * results.
- *
- * The 'key ID' is what is the most compact key value to drive
- * the hash, not class->key.
- */
- /*
- * Whoops, we did it again.. class_idx is invalid.
- */
- if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
- return 0;
- chain_key = curr->curr_chain_key;
- if (!depth) {
- /*
- * How can we have a chain hash when we ain't got no keys?!
- */
- if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
- return 0;
- chain_head = 1;
- }
- hlock->prev_chain_key = chain_key;
- if (separate_irq_context(curr, hlock)) {
- chain_key = INITIAL_CHAIN_KEY;
- chain_head = 1;
- }
- chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
- if (nest_lock && !__lock_is_held(nest_lock, -1)) {
- print_lock_nested_lock_not_held(curr, hlock);
- return 0;
- }
- if (!debug_locks_silent) {
- WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
- WARN_ON_ONCE(!hlock_class(hlock)->key);
- }
- if (!validate_chain(curr, hlock, chain_head, chain_key))
- return 0;
- curr->curr_chain_key = chain_key;
- curr->lockdep_depth++;
- check_chain_key(curr);
- #ifdef CONFIG_DEBUG_LOCKDEP
- if (unlikely(!debug_locks))
- return 0;
- #endif
- if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
- debug_locks_off();
- print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
- printk(KERN_DEBUG "depth: %i max: %lu!\n",
- curr->lockdep_depth, MAX_LOCK_DEPTH);
- lockdep_print_held_locks(current);
- debug_show_all_locks();
- dump_stack();
- return 0;
- }
- if (unlikely(curr->lockdep_depth > max_lockdep_depth))
- max_lockdep_depth = curr->lockdep_depth;
- return 1;
- }
- static void print_unlock_imbalance_bug(struct task_struct *curr,
- struct lockdep_map *lock,
- unsigned long ip)
- {
- if (!debug_locks_off())
- return;
- if (debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("=====================================\n");
- pr_warn("WARNING: bad unlock balance detected!\n");
- print_kernel_ident();
- pr_warn("-------------------------------------\n");
- pr_warn("%s/%d is trying to release lock (",
- curr->comm, task_pid_nr(curr));
- print_lockdep_cache(lock);
- pr_cont(") at:\n");
- print_ip_sym(KERN_WARNING, ip);
- pr_warn("but there are no more locks to release!\n");
- pr_warn("\nother info that might help us debug this:\n");
- lockdep_print_held_locks(curr);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- static noinstr int match_held_lock(const struct held_lock *hlock,
- const struct lockdep_map *lock)
- {
- if (hlock->instance == lock)
- return 1;
- if (hlock->references) {
- const struct lock_class *class = lock->class_cache[0];
- if (!class)
- class = look_up_lock_class(lock, 0);
- /*
- * If look_up_lock_class() failed to find a class, we're trying
- * to test if we hold a lock that has never yet been acquired.
- * Clearly if the lock hasn't been acquired _ever_, we're not
- * holding it either, so report failure.
- */
- if (!class)
- return 0;
- /*
- * References, but not a lock we're actually ref-counting?
- * State got messed up, follow the sites that change ->references
- * and try to make sense of it.
- */
- if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
- return 0;
- if (hlock->class_idx == class - lock_classes)
- return 1;
- }
- return 0;
- }
- /* @depth must not be zero */
- static struct held_lock *find_held_lock(struct task_struct *curr,
- struct lockdep_map *lock,
- unsigned int depth, int *idx)
- {
- struct held_lock *ret, *hlock, *prev_hlock;
- int i;
- i = depth - 1;
- hlock = curr->held_locks + i;
- ret = hlock;
- if (match_held_lock(hlock, lock))
- goto out;
- ret = NULL;
- for (i--, prev_hlock = hlock--;
- i >= 0;
- i--, prev_hlock = hlock--) {
- /*
- * We must not cross into another context:
- */
- if (prev_hlock->irq_context != hlock->irq_context) {
- ret = NULL;
- break;
- }
- if (match_held_lock(hlock, lock)) {
- ret = hlock;
- break;
- }
- }
- out:
- *idx = i;
- return ret;
- }
- static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
- int idx, unsigned int *merged)
- {
- struct held_lock *hlock;
- int first_idx = idx;
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return 0;
- for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
- switch (__lock_acquire(hlock->instance,
- hlock_class(hlock)->subclass,
- hlock->trylock,
- hlock->read, hlock->check,
- hlock->hardirqs_off,
- hlock->nest_lock, hlock->acquire_ip,
- hlock->references, hlock->pin_count)) {
- case 0:
- return 1;
- case 1:
- break;
- case 2:
- *merged += (idx == first_idx);
- break;
- default:
- WARN_ON(1);
- return 0;
- }
- }
- return 0;
- }
- static int
- __lock_set_class(struct lockdep_map *lock, const char *name,
- struct lock_class_key *key, unsigned int subclass,
- unsigned long ip)
- {
- struct task_struct *curr = current;
- unsigned int depth, merged = 0;
- struct held_lock *hlock;
- struct lock_class *class;
- int i;
- if (unlikely(!debug_locks))
- return 0;
- depth = curr->lockdep_depth;
- /*
- * This function is about (re)setting the class of a held lock,
- * yet we're not actually holding any locks. Naughty user!
- */
- if (DEBUG_LOCKS_WARN_ON(!depth))
- return 0;
- hlock = find_held_lock(curr, lock, depth, &i);
- if (!hlock) {
- print_unlock_imbalance_bug(curr, lock, ip);
- return 0;
- }
- lockdep_init_map_type(lock, name, key, 0,
- lock->wait_type_inner,
- lock->wait_type_outer,
- lock->lock_type);
- class = register_lock_class(lock, subclass, 0);
- hlock->class_idx = class - lock_classes;
- curr->lockdep_depth = i;
- curr->curr_chain_key = hlock->prev_chain_key;
- if (reacquire_held_locks(curr, depth, i, &merged))
- return 0;
- /*
- * I took it apart and put it back together again, except now I have
- * these 'spare' parts.. where shall I put them.
- */
- if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
- return 0;
- return 1;
- }
- static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
- {
- struct task_struct *curr = current;
- unsigned int depth, merged = 0;
- struct held_lock *hlock;
- int i;
- if (unlikely(!debug_locks))
- return 0;
- depth = curr->lockdep_depth;
- /*
- * This function is about (re)setting the class of a held lock,
- * yet we're not actually holding any locks. Naughty user!
- */
- if (DEBUG_LOCKS_WARN_ON(!depth))
- return 0;
- hlock = find_held_lock(curr, lock, depth, &i);
- if (!hlock) {
- print_unlock_imbalance_bug(curr, lock, ip);
- return 0;
- }
- curr->lockdep_depth = i;
- curr->curr_chain_key = hlock->prev_chain_key;
- WARN(hlock->read, "downgrading a read lock");
- hlock->read = 1;
- hlock->acquire_ip = ip;
- if (reacquire_held_locks(curr, depth, i, &merged))
- return 0;
- /* Merging can't happen with unchanged classes.. */
- if (DEBUG_LOCKS_WARN_ON(merged))
- return 0;
- /*
- * I took it apart and put it back together again, except now I have
- * these 'spare' parts.. where shall I put them.
- */
- if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
- return 0;
- return 1;
- }
- /*
- * Remove the lock from the list of currently held locks - this gets
- * called on mutex_unlock()/spin_unlock*() (or on a failed
- * mutex_lock_interruptible()).
- */
- static int
- __lock_release(struct lockdep_map *lock, unsigned long ip)
- {
- struct task_struct *curr = current;
- unsigned int depth, merged = 1;
- struct held_lock *hlock;
- int i;
- if (unlikely(!debug_locks))
- return 0;
- depth = curr->lockdep_depth;
- /*
- * So we're all set to release this lock.. wait what lock? We don't
- * own any locks, you've been drinking again?
- */
- if (depth <= 0) {
- print_unlock_imbalance_bug(curr, lock, ip);
- return 0;
- }
- /*
- * Check whether the lock exists in the current stack
- * of held locks:
- */
- hlock = find_held_lock(curr, lock, depth, &i);
- if (!hlock) {
- print_unlock_imbalance_bug(curr, lock, ip);
- return 0;
- }
- if (hlock->instance == lock)
- lock_release_holdtime(hlock);
- WARN(hlock->pin_count, "releasing a pinned lock\n");
- if (hlock->references) {
- hlock->references--;
- if (hlock->references) {
- /*
- * We had, and after removing one, still have
- * references, the current lock stack is still
- * valid. We're done!
- */
- return 1;
- }
- }
- /*
- * We have the right lock to unlock, 'hlock' points to it.
- * Now we remove it from the stack, and add back the other
- * entries (if any), recalculating the hash along the way:
- */
- curr->lockdep_depth = i;
- curr->curr_chain_key = hlock->prev_chain_key;
- /*
- * The most likely case is when the unlock is on the innermost
- * lock. In this case, we are done!
- */
- if (i == depth-1)
- return 1;
- if (reacquire_held_locks(curr, depth, i + 1, &merged))
- return 0;
- /*
- * We had N bottles of beer on the wall, we drank one, but now
- * there's not N-1 bottles of beer left on the wall...
- * Pouring two of the bottles together is acceptable.
- */
- DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
- /*
- * Since reacquire_held_locks() would have called check_chain_key()
- * indirectly via __lock_acquire(), we don't need to do it again
- * on return.
- */
- return 0;
- }
- static __always_inline
- int __lock_is_held(const struct lockdep_map *lock, int read)
- {
- struct task_struct *curr = current;
- int i;
- for (i = 0; i < curr->lockdep_depth; i++) {
- struct held_lock *hlock = curr->held_locks + i;
- if (match_held_lock(hlock, lock)) {
- if (read == -1 || !!hlock->read == read)
- return LOCK_STATE_HELD;
- return LOCK_STATE_NOT_HELD;
- }
- }
- return LOCK_STATE_NOT_HELD;
- }
- static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
- {
- struct pin_cookie cookie = NIL_COOKIE;
- struct task_struct *curr = current;
- int i;
- if (unlikely(!debug_locks))
- return cookie;
- for (i = 0; i < curr->lockdep_depth; i++) {
- struct held_lock *hlock = curr->held_locks + i;
- if (match_held_lock(hlock, lock)) {
- /*
- * Grab 16bits of randomness; this is sufficient to not
- * be guessable and still allows some pin nesting in
- * our u32 pin_count.
- */
- cookie.val = 1 + (sched_clock() & 0xffff);
- hlock->pin_count += cookie.val;
- return cookie;
- }
- }
- WARN(1, "pinning an unheld lock\n");
- return cookie;
- }
- static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
- {
- struct task_struct *curr = current;
- int i;
- if (unlikely(!debug_locks))
- return;
- for (i = 0; i < curr->lockdep_depth; i++) {
- struct held_lock *hlock = curr->held_locks + i;
- if (match_held_lock(hlock, lock)) {
- hlock->pin_count += cookie.val;
- return;
- }
- }
- WARN(1, "pinning an unheld lock\n");
- }
- static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
- {
- struct task_struct *curr = current;
- int i;
- if (unlikely(!debug_locks))
- return;
- for (i = 0; i < curr->lockdep_depth; i++) {
- struct held_lock *hlock = curr->held_locks + i;
- if (match_held_lock(hlock, lock)) {
- if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
- return;
- hlock->pin_count -= cookie.val;
- if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
- hlock->pin_count = 0;
- return;
- }
- }
- WARN(1, "unpinning an unheld lock\n");
- }
- /*
- * Check whether we follow the irq-flags state precisely:
- */
- static noinstr void check_flags(unsigned long flags)
- {
- #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
- if (!debug_locks)
- return;
- /* Get the warning out.. */
- instrumentation_begin();
- if (irqs_disabled_flags(flags)) {
- if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
- printk("possible reason: unannotated irqs-off.\n");
- }
- } else {
- if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
- printk("possible reason: unannotated irqs-on.\n");
- }
- }
- #ifndef CONFIG_PREEMPT_RT
- /*
- * We dont accurately track softirq state in e.g.
- * hardirq contexts (such as on 4KSTACKS), so only
- * check if not in hardirq contexts:
- */
- if (!hardirq_count()) {
- if (softirq_count()) {
- /* like the above, but with softirqs */
- DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
- } else {
- /* lick the above, does it taste good? */
- DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
- }
- }
- #endif
- if (!debug_locks)
- print_irqtrace_events(current);
- instrumentation_end();
- #endif
- }
- void lock_set_class(struct lockdep_map *lock, const char *name,
- struct lock_class_key *key, unsigned int subclass,
- unsigned long ip)
- {
- unsigned long flags;
- if (unlikely(!lockdep_enabled()))
- return;
- raw_local_irq_save(flags);
- lockdep_recursion_inc();
- check_flags(flags);
- if (__lock_set_class(lock, name, key, subclass, ip))
- check_chain_key(current);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lock_set_class);
- void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
- {
- unsigned long flags;
- if (unlikely(!lockdep_enabled()))
- return;
- raw_local_irq_save(flags);
- lockdep_recursion_inc();
- check_flags(flags);
- if (__lock_downgrade(lock, ip))
- check_chain_key(current);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lock_downgrade);
- /* NMI context !!! */
- static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
- {
- #ifdef CONFIG_PROVE_LOCKING
- struct lock_class *class = look_up_lock_class(lock, subclass);
- unsigned long mask = LOCKF_USED;
- /* if it doesn't have a class (yet), it certainly hasn't been used yet */
- if (!class)
- return;
- /*
- * READ locks only conflict with USED, such that if we only ever use
- * READ locks, there is no deadlock possible -- RCU.
- */
- if (!hlock->read)
- mask |= LOCKF_USED_READ;
- if (!(class->usage_mask & mask))
- return;
- hlock->class_idx = class - lock_classes;
- print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
- #endif
- }
- static bool lockdep_nmi(void)
- {
- if (raw_cpu_read(lockdep_recursion))
- return false;
- if (!in_nmi())
- return false;
- return true;
- }
- /*
- * read_lock() is recursive if:
- * 1. We force lockdep think this way in selftests or
- * 2. The implementation is not queued read/write lock or
- * 3. The locker is at an in_interrupt() context.
- */
- bool read_lock_is_recursive(void)
- {
- return force_read_lock_recursive ||
- !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
- in_interrupt();
- }
- EXPORT_SYMBOL_GPL(read_lock_is_recursive);
- /*
- * We are not always called with irqs disabled - do that here,
- * and also avoid lockdep recursion:
- */
- void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
- int trylock, int read, int check,
- struct lockdep_map *nest_lock, unsigned long ip)
- {
- unsigned long flags;
- trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
- if (!debug_locks)
- return;
- if (unlikely(!lockdep_enabled())) {
- /* XXX allow trylock from NMI ?!? */
- if (lockdep_nmi() && !trylock) {
- struct held_lock hlock;
- hlock.acquire_ip = ip;
- hlock.instance = lock;
- hlock.nest_lock = nest_lock;
- hlock.irq_context = 2; // XXX
- hlock.trylock = trylock;
- hlock.read = read;
- hlock.check = check;
- hlock.hardirqs_off = true;
- hlock.references = 0;
- verify_lock_unused(lock, &hlock, subclass);
- }
- return;
- }
- raw_local_irq_save(flags);
- check_flags(flags);
- lockdep_recursion_inc();
- __lock_acquire(lock, subclass, trylock, read, check,
- irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lock_acquire);
- void lock_release(struct lockdep_map *lock, unsigned long ip)
- {
- unsigned long flags;
- trace_lock_release(lock, ip);
- if (unlikely(!lockdep_enabled()))
- return;
- raw_local_irq_save(flags);
- check_flags(flags);
- lockdep_recursion_inc();
- if (__lock_release(lock, ip))
- check_chain_key(current);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lock_release);
- noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
- {
- unsigned long flags;
- int ret = LOCK_STATE_NOT_HELD;
- /*
- * Avoid false negative lockdep_assert_held() and
- * lockdep_assert_not_held().
- */
- if (unlikely(!lockdep_enabled()))
- return LOCK_STATE_UNKNOWN;
- raw_local_irq_save(flags);
- check_flags(flags);
- lockdep_recursion_inc();
- ret = __lock_is_held(lock, read);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- return ret;
- }
- EXPORT_SYMBOL_GPL(lock_is_held_type);
- NOKPROBE_SYMBOL(lock_is_held_type);
- struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
- {
- struct pin_cookie cookie = NIL_COOKIE;
- unsigned long flags;
- if (unlikely(!lockdep_enabled()))
- return cookie;
- raw_local_irq_save(flags);
- check_flags(flags);
- lockdep_recursion_inc();
- cookie = __lock_pin_lock(lock);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- return cookie;
- }
- EXPORT_SYMBOL_GPL(lock_pin_lock);
- void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
- {
- unsigned long flags;
- if (unlikely(!lockdep_enabled()))
- return;
- raw_local_irq_save(flags);
- check_flags(flags);
- lockdep_recursion_inc();
- __lock_repin_lock(lock, cookie);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lock_repin_lock);
- void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
- {
- unsigned long flags;
- if (unlikely(!lockdep_enabled()))
- return;
- raw_local_irq_save(flags);
- check_flags(flags);
- lockdep_recursion_inc();
- __lock_unpin_lock(lock, cookie);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lock_unpin_lock);
- #ifdef CONFIG_LOCK_STAT
- static void print_lock_contention_bug(struct task_struct *curr,
- struct lockdep_map *lock,
- unsigned long ip)
- {
- if (!debug_locks_off())
- return;
- if (debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("=================================\n");
- pr_warn("WARNING: bad contention detected!\n");
- print_kernel_ident();
- pr_warn("---------------------------------\n");
- pr_warn("%s/%d is trying to contend lock (",
- curr->comm, task_pid_nr(curr));
- print_lockdep_cache(lock);
- pr_cont(") at:\n");
- print_ip_sym(KERN_WARNING, ip);
- pr_warn("but there are no locks held!\n");
- pr_warn("\nother info that might help us debug this:\n");
- lockdep_print_held_locks(curr);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- static void
- __lock_contended(struct lockdep_map *lock, unsigned long ip)
- {
- struct task_struct *curr = current;
- struct held_lock *hlock;
- struct lock_class_stats *stats;
- unsigned int depth;
- int i, contention_point, contending_point;
- depth = curr->lockdep_depth;
- /*
- * Whee, we contended on this lock, except it seems we're not
- * actually trying to acquire anything much at all..
- */
- if (DEBUG_LOCKS_WARN_ON(!depth))
- return;
- hlock = find_held_lock(curr, lock, depth, &i);
- if (!hlock) {
- print_lock_contention_bug(curr, lock, ip);
- return;
- }
- if (hlock->instance != lock)
- return;
- hlock->waittime_stamp = lockstat_clock();
- contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
- contending_point = lock_point(hlock_class(hlock)->contending_point,
- lock->ip);
- stats = get_lock_stats(hlock_class(hlock));
- if (contention_point < LOCKSTAT_POINTS)
- stats->contention_point[contention_point]++;
- if (contending_point < LOCKSTAT_POINTS)
- stats->contending_point[contending_point]++;
- if (lock->cpu != smp_processor_id())
- stats->bounces[bounce_contended + !!hlock->read]++;
- }
- static void
- __lock_acquired(struct lockdep_map *lock, unsigned long ip)
- {
- struct task_struct *curr = current;
- struct held_lock *hlock;
- struct lock_class_stats *stats;
- unsigned int depth;
- u64 now, waittime = 0;
- int i, cpu;
- depth = curr->lockdep_depth;
- /*
- * Yay, we acquired ownership of this lock we didn't try to
- * acquire, how the heck did that happen?
- */
- if (DEBUG_LOCKS_WARN_ON(!depth))
- return;
- hlock = find_held_lock(curr, lock, depth, &i);
- if (!hlock) {
- print_lock_contention_bug(curr, lock, _RET_IP_);
- return;
- }
- if (hlock->instance != lock)
- return;
- cpu = smp_processor_id();
- if (hlock->waittime_stamp) {
- now = lockstat_clock();
- waittime = now - hlock->waittime_stamp;
- hlock->holdtime_stamp = now;
- }
- stats = get_lock_stats(hlock_class(hlock));
- if (waittime) {
- if (hlock->read)
- lock_time_inc(&stats->read_waittime, waittime);
- else
- lock_time_inc(&stats->write_waittime, waittime);
- }
- if (lock->cpu != cpu)
- stats->bounces[bounce_acquired + !!hlock->read]++;
- lock->cpu = cpu;
- lock->ip = ip;
- }
- void lock_contended(struct lockdep_map *lock, unsigned long ip)
- {
- unsigned long flags;
- trace_lock_contended(lock, ip);
- if (unlikely(!lock_stat || !lockdep_enabled()))
- return;
- raw_local_irq_save(flags);
- check_flags(flags);
- lockdep_recursion_inc();
- __lock_contended(lock, ip);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lock_contended);
- void lock_acquired(struct lockdep_map *lock, unsigned long ip)
- {
- unsigned long flags;
- trace_lock_acquired(lock, ip);
- if (unlikely(!lock_stat || !lockdep_enabled()))
- return;
- raw_local_irq_save(flags);
- check_flags(flags);
- lockdep_recursion_inc();
- __lock_acquired(lock, ip);
- lockdep_recursion_finish();
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(lock_acquired);
- #endif
- /*
- * Used by the testsuite, sanitize the validator state
- * after a simulated failure:
- */
- void lockdep_reset(void)
- {
- unsigned long flags;
- int i;
- raw_local_irq_save(flags);
- lockdep_init_task(current);
- memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
- nr_hardirq_chains = 0;
- nr_softirq_chains = 0;
- nr_process_chains = 0;
- debug_locks = 1;
- for (i = 0; i < CHAINHASH_SIZE; i++)
- INIT_HLIST_HEAD(chainhash_table + i);
- raw_local_irq_restore(flags);
- }
- /* Remove a class from a lock chain. Must be called with the graph lock held. */
- static void remove_class_from_lock_chain(struct pending_free *pf,
- struct lock_chain *chain,
- struct lock_class *class)
- {
- #ifdef CONFIG_PROVE_LOCKING
- int i;
- for (i = chain->base; i < chain->base + chain->depth; i++) {
- if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
- continue;
- /*
- * Each lock class occurs at most once in a lock chain so once
- * we found a match we can break out of this loop.
- */
- goto free_lock_chain;
- }
- /* Since the chain has not been modified, return. */
- return;
- free_lock_chain:
- free_chain_hlocks(chain->base, chain->depth);
- /* Overwrite the chain key for concurrent RCU readers. */
- WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
- dec_chains(chain->irq_context);
- /*
- * Note: calling hlist_del_rcu() from inside a
- * hlist_for_each_entry_rcu() loop is safe.
- */
- hlist_del_rcu(&chain->entry);
- __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
- nr_zapped_lock_chains++;
- #endif
- }
- /* Must be called with the graph lock held. */
- static void remove_class_from_lock_chains(struct pending_free *pf,
- struct lock_class *class)
- {
- struct lock_chain *chain;
- struct hlist_head *head;
- int i;
- for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
- head = chainhash_table + i;
- hlist_for_each_entry_rcu(chain, head, entry) {
- remove_class_from_lock_chain(pf, chain, class);
- }
- }
- }
- /*
- * Remove all references to a lock class. The caller must hold the graph lock.
- */
- static void zap_class(struct pending_free *pf, struct lock_class *class)
- {
- struct lock_list *entry;
- int i;
- WARN_ON_ONCE(!class->key);
- /*
- * Remove all dependencies this lock is
- * involved in:
- */
- for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
- entry = list_entries + i;
- if (entry->class != class && entry->links_to != class)
- continue;
- __clear_bit(i, list_entries_in_use);
- nr_list_entries--;
- list_del_rcu(&entry->entry);
- }
- if (list_empty(&class->locks_after) &&
- list_empty(&class->locks_before)) {
- list_move_tail(&class->lock_entry, &pf->zapped);
- hlist_del_rcu(&class->hash_entry);
- WRITE_ONCE(class->key, NULL);
- WRITE_ONCE(class->name, NULL);
- nr_lock_classes--;
- __clear_bit(class - lock_classes, lock_classes_in_use);
- if (class - lock_classes == max_lock_class_idx)
- max_lock_class_idx--;
- } else {
- WARN_ONCE(true, "%s() failed for class %s\n", __func__,
- class->name);
- }
- remove_class_from_lock_chains(pf, class);
- nr_zapped_classes++;
- }
- static void reinit_class(struct lock_class *class)
- {
- WARN_ON_ONCE(!class->lock_entry.next);
- WARN_ON_ONCE(!list_empty(&class->locks_after));
- WARN_ON_ONCE(!list_empty(&class->locks_before));
- memset_startat(class, 0, key);
- WARN_ON_ONCE(!class->lock_entry.next);
- WARN_ON_ONCE(!list_empty(&class->locks_after));
- WARN_ON_ONCE(!list_empty(&class->locks_before));
- }
- static inline int within(const void *addr, void *start, unsigned long size)
- {
- return addr >= start && addr < start + size;
- }
- static bool inside_selftest(void)
- {
- return current == lockdep_selftest_task_struct;
- }
- /* The caller must hold the graph lock. */
- static struct pending_free *get_pending_free(void)
- {
- return delayed_free.pf + delayed_free.index;
- }
- static void free_zapped_rcu(struct rcu_head *cb);
- /*
- * Schedule an RCU callback if no RCU callback is pending. Must be called with
- * the graph lock held.
- */
- static void call_rcu_zapped(struct pending_free *pf)
- {
- WARN_ON_ONCE(inside_selftest());
- if (list_empty(&pf->zapped))
- return;
- if (delayed_free.scheduled)
- return;
- delayed_free.scheduled = true;
- WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
- delayed_free.index ^= 1;
- call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
- }
- /* The caller must hold the graph lock. May be called from RCU context. */
- static void __free_zapped_classes(struct pending_free *pf)
- {
- struct lock_class *class;
- check_data_structures();
- list_for_each_entry(class, &pf->zapped, lock_entry)
- reinit_class(class);
- list_splice_init(&pf->zapped, &free_lock_classes);
- #ifdef CONFIG_PROVE_LOCKING
- bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
- pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
- bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
- #endif
- }
- static void free_zapped_rcu(struct rcu_head *ch)
- {
- struct pending_free *pf;
- unsigned long flags;
- if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
- return;
- raw_local_irq_save(flags);
- lockdep_lock();
- /* closed head */
- pf = delayed_free.pf + (delayed_free.index ^ 1);
- __free_zapped_classes(pf);
- delayed_free.scheduled = false;
- /*
- * If there's anything on the open list, close and start a new callback.
- */
- call_rcu_zapped(delayed_free.pf + delayed_free.index);
- lockdep_unlock();
- raw_local_irq_restore(flags);
- }
- /*
- * Remove all lock classes from the class hash table and from the
- * all_lock_classes list whose key or name is in the address range [start,
- * start + size). Move these lock classes to the zapped_classes list. Must
- * be called with the graph lock held.
- */
- static void __lockdep_free_key_range(struct pending_free *pf, void *start,
- unsigned long size)
- {
- struct lock_class *class;
- struct hlist_head *head;
- int i;
- /* Unhash all classes that were created by a module. */
- for (i = 0; i < CLASSHASH_SIZE; i++) {
- head = classhash_table + i;
- hlist_for_each_entry_rcu(class, head, hash_entry) {
- if (!within(class->key, start, size) &&
- !within(class->name, start, size))
- continue;
- zap_class(pf, class);
- }
- }
- }
- /*
- * Used in module.c to remove lock classes from memory that is going to be
- * freed; and possibly re-used by other modules.
- *
- * We will have had one synchronize_rcu() before getting here, so we're
- * guaranteed nobody will look up these exact classes -- they're properly dead
- * but still allocated.
- */
- static void lockdep_free_key_range_reg(void *start, unsigned long size)
- {
- struct pending_free *pf;
- unsigned long flags;
- init_data_structures_once();
- raw_local_irq_save(flags);
- lockdep_lock();
- pf = get_pending_free();
- __lockdep_free_key_range(pf, start, size);
- call_rcu_zapped(pf);
- lockdep_unlock();
- raw_local_irq_restore(flags);
- /*
- * Wait for any possible iterators from look_up_lock_class() to pass
- * before continuing to free the memory they refer to.
- */
- synchronize_rcu();
- }
- /*
- * Free all lockdep keys in the range [start, start+size). Does not sleep.
- * Ignores debug_locks. Must only be used by the lockdep selftests.
- */
- static void lockdep_free_key_range_imm(void *start, unsigned long size)
- {
- struct pending_free *pf = delayed_free.pf;
- unsigned long flags;
- init_data_structures_once();
- raw_local_irq_save(flags);
- lockdep_lock();
- __lockdep_free_key_range(pf, start, size);
- __free_zapped_classes(pf);
- lockdep_unlock();
- raw_local_irq_restore(flags);
- }
- void lockdep_free_key_range(void *start, unsigned long size)
- {
- init_data_structures_once();
- if (inside_selftest())
- lockdep_free_key_range_imm(start, size);
- else
- lockdep_free_key_range_reg(start, size);
- }
- /*
- * Check whether any element of the @lock->class_cache[] array refers to a
- * registered lock class. The caller must hold either the graph lock or the
- * RCU read lock.
- */
- static bool lock_class_cache_is_registered(struct lockdep_map *lock)
- {
- struct lock_class *class;
- struct hlist_head *head;
- int i, j;
- for (i = 0; i < CLASSHASH_SIZE; i++) {
- head = classhash_table + i;
- hlist_for_each_entry_rcu(class, head, hash_entry) {
- for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
- if (lock->class_cache[j] == class)
- return true;
- }
- }
- return false;
- }
- /* The caller must hold the graph lock. Does not sleep. */
- static void __lockdep_reset_lock(struct pending_free *pf,
- struct lockdep_map *lock)
- {
- struct lock_class *class;
- int j;
- /*
- * Remove all classes this lock might have:
- */
- for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
- /*
- * If the class exists we look it up and zap it:
- */
- class = look_up_lock_class(lock, j);
- if (class)
- zap_class(pf, class);
- }
- /*
- * Debug check: in the end all mapped classes should
- * be gone.
- */
- if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
- debug_locks_off();
- }
- /*
- * Remove all information lockdep has about a lock if debug_locks == 1. Free
- * released data structures from RCU context.
- */
- static void lockdep_reset_lock_reg(struct lockdep_map *lock)
- {
- struct pending_free *pf;
- unsigned long flags;
- int locked;
- raw_local_irq_save(flags);
- locked = graph_lock();
- if (!locked)
- goto out_irq;
- pf = get_pending_free();
- __lockdep_reset_lock(pf, lock);
- call_rcu_zapped(pf);
- graph_unlock();
- out_irq:
- raw_local_irq_restore(flags);
- }
- /*
- * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
- * lockdep selftests.
- */
- static void lockdep_reset_lock_imm(struct lockdep_map *lock)
- {
- struct pending_free *pf = delayed_free.pf;
- unsigned long flags;
- raw_local_irq_save(flags);
- lockdep_lock();
- __lockdep_reset_lock(pf, lock);
- __free_zapped_classes(pf);
- lockdep_unlock();
- raw_local_irq_restore(flags);
- }
- void lockdep_reset_lock(struct lockdep_map *lock)
- {
- init_data_structures_once();
- if (inside_selftest())
- lockdep_reset_lock_imm(lock);
- else
- lockdep_reset_lock_reg(lock);
- }
- /*
- * Unregister a dynamically allocated key.
- *
- * Unlike lockdep_register_key(), a search is always done to find a matching
- * key irrespective of debug_locks to avoid potential invalid access to freed
- * memory in lock_class entry.
- */
- void lockdep_unregister_key(struct lock_class_key *key)
- {
- struct hlist_head *hash_head = keyhashentry(key);
- struct lock_class_key *k;
- struct pending_free *pf;
- unsigned long flags;
- bool found = false;
- might_sleep();
- if (WARN_ON_ONCE(static_obj(key)))
- return;
- raw_local_irq_save(flags);
- lockdep_lock();
- hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
- if (k == key) {
- hlist_del_rcu(&k->hash_entry);
- found = true;
- break;
- }
- }
- WARN_ON_ONCE(!found && debug_locks);
- if (found) {
- pf = get_pending_free();
- __lockdep_free_key_range(pf, key, 1);
- call_rcu_zapped(pf);
- }
- lockdep_unlock();
- raw_local_irq_restore(flags);
- /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
- synchronize_rcu();
- }
- EXPORT_SYMBOL_GPL(lockdep_unregister_key);
- void __init lockdep_init(void)
- {
- printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
- printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
- printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
- printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
- printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
- printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
- printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
- printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
- printk(" memory used by lock dependency info: %zu kB\n",
- (sizeof(lock_classes) +
- sizeof(lock_classes_in_use) +
- sizeof(classhash_table) +
- sizeof(list_entries) +
- sizeof(list_entries_in_use) +
- sizeof(chainhash_table) +
- sizeof(delayed_free)
- #ifdef CONFIG_PROVE_LOCKING
- + sizeof(lock_cq)
- + sizeof(lock_chains)
- + sizeof(lock_chains_in_use)
- + sizeof(chain_hlocks)
- #endif
- ) / 1024
- );
- #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
- printk(" memory used for stack traces: %zu kB\n",
- (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
- );
- #endif
- printk(" per task-struct memory footprint: %zu bytes\n",
- sizeof(((struct task_struct *)NULL)->held_locks));
- }
- static void
- print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
- const void *mem_to, struct held_lock *hlock)
- {
- if (!debug_locks_off())
- return;
- if (debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("=========================\n");
- pr_warn("WARNING: held lock freed!\n");
- print_kernel_ident();
- pr_warn("-------------------------\n");
- pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
- curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
- print_lock(hlock);
- lockdep_print_held_locks(curr);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- static inline int not_in_range(const void* mem_from, unsigned long mem_len,
- const void* lock_from, unsigned long lock_len)
- {
- return lock_from + lock_len <= mem_from ||
- mem_from + mem_len <= lock_from;
- }
- /*
- * Called when kernel memory is freed (or unmapped), or if a lock
- * is destroyed or reinitialized - this code checks whether there is
- * any held lock in the memory range of <from> to <to>:
- */
- void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
- {
- struct task_struct *curr = current;
- struct held_lock *hlock;
- unsigned long flags;
- int i;
- if (unlikely(!debug_locks))
- return;
- raw_local_irq_save(flags);
- for (i = 0; i < curr->lockdep_depth; i++) {
- hlock = curr->held_locks + i;
- if (not_in_range(mem_from, mem_len, hlock->instance,
- sizeof(*hlock->instance)))
- continue;
- print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
- break;
- }
- raw_local_irq_restore(flags);
- }
- EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
- static void print_held_locks_bug(void)
- {
- if (!debug_locks_off())
- return;
- if (debug_locks_silent)
- return;
- pr_warn("\n");
- pr_warn("====================================\n");
- pr_warn("WARNING: %s/%d still has locks held!\n",
- current->comm, task_pid_nr(current));
- print_kernel_ident();
- pr_warn("------------------------------------\n");
- lockdep_print_held_locks(current);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- }
- void debug_check_no_locks_held(void)
- {
- if (unlikely(current->lockdep_depth > 0))
- print_held_locks_bug();
- }
- EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
- #ifdef __KERNEL__
- void debug_show_all_locks(void)
- {
- struct task_struct *g, *p;
- if (unlikely(!debug_locks)) {
- pr_warn("INFO: lockdep is turned off.\n");
- return;
- }
- pr_warn("\nShowing all locks held in the system:\n");
- rcu_read_lock();
- for_each_process_thread(g, p) {
- if (!p->lockdep_depth)
- continue;
- lockdep_print_held_locks(p);
- touch_nmi_watchdog();
- touch_all_softlockup_watchdogs();
- }
- rcu_read_unlock();
- pr_warn("\n");
- pr_warn("=============================================\n\n");
- }
- EXPORT_SYMBOL_GPL(debug_show_all_locks);
- #endif
- /*
- * Careful: only use this function if you are sure that
- * the task cannot run in parallel!
- */
- void debug_show_held_locks(struct task_struct *task)
- {
- if (unlikely(!debug_locks)) {
- printk("INFO: lockdep is turned off.\n");
- return;
- }
- lockdep_print_held_locks(task);
- }
- EXPORT_SYMBOL_GPL(debug_show_held_locks);
- asmlinkage __visible void lockdep_sys_exit(void)
- {
- struct task_struct *curr = current;
- if (unlikely(curr->lockdep_depth)) {
- if (!debug_locks_off())
- return;
- pr_warn("\n");
- pr_warn("================================================\n");
- pr_warn("WARNING: lock held when returning to user space!\n");
- print_kernel_ident();
- pr_warn("------------------------------------------------\n");
- pr_warn("%s/%d is leaving the kernel with locks still held!\n",
- curr->comm, curr->pid);
- lockdep_print_held_locks(curr);
- }
- /*
- * The lock history for each syscall should be independent. So wipe the
- * slate clean on return to userspace.
- */
- lockdep_invariant_state(false);
- }
- void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
- {
- struct task_struct *curr = current;
- int dl = READ_ONCE(debug_locks);
- bool rcu = warn_rcu_enter();
- /* Note: the following can be executed concurrently, so be careful. */
- pr_warn("\n");
- pr_warn("=============================\n");
- pr_warn("WARNING: suspicious RCU usage\n");
- print_kernel_ident();
- pr_warn("-----------------------------\n");
- pr_warn("%s:%d %s!\n", file, line, s);
- pr_warn("\nother info that might help us debug this:\n\n");
- pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s",
- !rcu_lockdep_current_cpu_online()
- ? "RCU used illegally from offline CPU!\n"
- : "",
- rcu_scheduler_active, dl,
- dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
- /*
- * If a CPU is in the RCU-free window in idle (ie: in the section
- * between ct_idle_enter() and ct_idle_exit(), then RCU
- * considers that CPU to be in an "extended quiescent state",
- * which means that RCU will be completely ignoring that CPU.
- * Therefore, rcu_read_lock() and friends have absolutely no
- * effect on a CPU running in that state. In other words, even if
- * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
- * delete data structures out from under it. RCU really has no
- * choice here: we need to keep an RCU-free window in idle where
- * the CPU may possibly enter into low power mode. This way we can
- * notice an extended quiescent state to other CPUs that started a grace
- * period. Otherwise we would delay any grace period as long as we run
- * in the idle task.
- *
- * So complain bitterly if someone does call rcu_read_lock(),
- * rcu_read_lock_bh() and so on from extended quiescent states.
- */
- if (!rcu_is_watching())
- pr_warn("RCU used illegally from extended quiescent state!\n");
- lockdep_print_held_locks(curr);
- pr_warn("\nstack backtrace:\n");
- dump_stack();
- warn_rcu_exit(rcu);
- }
- EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
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