tree/tiny rcu: Add debug RCU head objects
Helps finding racy users of call_rcu(), which results in hangs because list entries are overwritten and/or skipped. Changelog since v4: - Bissectability is now OK - Now generate a WARN_ON_ONCE() for non-initialized rcu_head passed to call_rcu(). Statically initialized objects are detected with object_is_static(). - Rename rcu_head_init_on_stack to init_rcu_head_on_stack. - Remove init_rcu_head() completely. Changelog since v3: - Include comments from Lai Jiangshan This new patch version is based on the debugobjects with the newly introduced "active state" tracker. Non-initialized entries are all considered as "statically initialized". An activation fixup (triggered by call_rcu()) takes care of performing the debug object initialization without issuing any warning. Since we cannot increase the size of struct rcu_head, I don't see much room to put an identifier for statically initialized rcu_head structures. So for now, we have to live without "activation without explicit init" detection. But the main purpose of this debug option is to detect double-activations (double call_rcu() use of a rcu_head before the callback is executed), which is correctly addressed here. This also detects potential internal RCU callback corruption, which would cause the callbacks to be executed twice. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> CC: David S. Miller <davem@davemloft.net> CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: tglx@linutronix.de CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
This commit is contained in:
Mathieu Desnoyers
committed by
Paul E. McKenney
Paul E. McKenney
parent
875352c942
commit
551d55a944
@@ -114,3 +114,163 @@ int rcu_my_thread_group_empty(void)
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}
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EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
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#endif /* #ifdef CONFIG_PROVE_RCU */
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#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
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static inline void debug_init_rcu_head(struct rcu_head *head)
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{
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debug_object_init(head, &rcuhead_debug_descr);
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}
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static inline void debug_rcu_head_free(struct rcu_head *head)
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{
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debug_object_free(head, &rcuhead_debug_descr);
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}
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/*
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* fixup_init is called when:
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* - an active object is initialized
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*/
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static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
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{
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struct rcu_head *head = addr;
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switch (state) {
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case ODEBUG_STATE_ACTIVE:
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/*
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* Ensure that queued callbacks are all executed.
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* If we detect that we are nested in a RCU read-side critical
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* section, we should simply fail, otherwise we would deadlock.
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*/
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if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
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irqs_disabled()) {
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WARN_ON(1);
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return 0;
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}
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rcu_barrier();
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rcu_barrier_sched();
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rcu_barrier_bh();
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debug_object_init(head, &rcuhead_debug_descr);
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return 1;
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default:
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return 0;
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}
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}
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/*
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* fixup_activate is called when:
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* - an active object is activated
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* - an unknown object is activated (might be a statically initialized object)
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* Activation is performed internally by call_rcu().
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*/
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static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
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{
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struct rcu_head *head = addr;
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switch (state) {
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case ODEBUG_STATE_NOTAVAILABLE:
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/*
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* This is not really a fixup. We just make sure that it is
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* tracked in the object tracker.
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*/
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debug_object_init(head, &rcuhead_debug_descr);
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debug_object_activate(head, &rcuhead_debug_descr);
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return 0;
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case ODEBUG_STATE_ACTIVE:
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/*
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* Ensure that queued callbacks are all executed.
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* If we detect that we are nested in a RCU read-side critical
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* section, we should simply fail, otherwise we would deadlock.
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*/
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if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
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irqs_disabled()) {
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WARN_ON(1);
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return 0;
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}
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rcu_barrier();
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rcu_barrier_sched();
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rcu_barrier_bh();
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debug_object_activate(head, &rcuhead_debug_descr);
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return 1;
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default:
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return 0;
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}
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}
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/*
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* fixup_free is called when:
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* - an active object is freed
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*/
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static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
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{
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struct rcu_head *head = addr;
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switch (state) {
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case ODEBUG_STATE_ACTIVE:
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/*
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* Ensure that queued callbacks are all executed.
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* If we detect that we are nested in a RCU read-side critical
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* section, we should simply fail, otherwise we would deadlock.
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*/
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#ifndef CONFIG_PREEMPT
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WARN_ON(1);
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return 0;
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#else
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if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
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irqs_disabled()) {
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WARN_ON(1);
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return 0;
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}
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rcu_barrier();
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rcu_barrier_sched();
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rcu_barrier_bh();
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debug_object_free(head, &rcuhead_debug_descr);
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return 1;
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#endif
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default:
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return 0;
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}
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}
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/**
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* init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
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* @head: pointer to rcu_head structure to be initialized
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*
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* This function informs debugobjects of a new rcu_head structure that
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* has been allocated as an auto variable on the stack. This function
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* is not required for rcu_head structures that are statically defined or
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* that are dynamically allocated on the heap. This function has no
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* effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
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*/
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void init_rcu_head_on_stack(struct rcu_head *head)
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{
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debug_object_init_on_stack(head, &rcuhead_debug_descr);
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}
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EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
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/**
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* destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
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* @head: pointer to rcu_head structure to be initialized
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*
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* This function informs debugobjects that an on-stack rcu_head structure
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* is about to go out of scope. As with init_rcu_head_on_stack(), this
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* function is not required for rcu_head structures that are statically
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* defined or that are dynamically allocated on the heap. Also as with
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* init_rcu_head_on_stack(), this function has no effect for
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* !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
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*/
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void destroy_rcu_head_on_stack(struct rcu_head *head)
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{
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debug_object_free(head, &rcuhead_debug_descr);
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}
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EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
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struct debug_obj_descr rcuhead_debug_descr = {
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.name = "rcu_head",
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.fixup_init = rcuhead_fixup_init,
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.fixup_activate = rcuhead_fixup_activate,
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.fixup_free = rcuhead_fixup_free,
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};
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EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
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#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
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