Merge branches 'consolidate.2019.08.01b', 'fixes.2019.08.12a', 'lists.2019.08.13a' and 'torture.2019.08.01b' into HEAD

consolidate.2019.08.01b: Further consolidation cleanups
fixes.2019.08.12a: Miscellaneous fixes
lists.2019.08.13a: Optional lockdep arguments for RCU list macros
torture.2019.08.01b: Torture-test updates

kernel/rcu/Kconfig.debug

@@ -8,6 +8,17 @@ menu "RCU Debugging"
 config PROVE_RCU
 	def_bool PROVE_LOCKING
 
+config PROVE_RCU_LIST
+	bool "RCU list lockdep debugging"
+	depends on PROVE_RCU && RCU_EXPERT
+	default n
+	help
+	  Enable RCU lockdep checking for list usages. By default it is
+	  turned off since there are several list RCU users that still
+	  need to be converted to pass a lockdep expression. To prevent
+	  false-positive splats, we keep it default disabled but once all
+	  users are converted, we can remove this config option.
+
 config TORTURE_TEST
 	tristate
 	default n

kernel/rcu/rcu.h

@@ -227,6 +227,7 @@ static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 
 #ifdef CONFIG_RCU_STALL_COMMON
 
+extern int rcu_cpu_stall_ftrace_dump;
 extern int rcu_cpu_stall_suppress;
 extern int rcu_cpu_stall_timeout;
 int rcu_jiffies_till_stall_check(void);

kernel/rcu/rcu_segcblist.h

@@ -76,27 +76,6 @@ static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
 	return !*rsclp->tails[seg];
 }
 
-/*
- * Interim function to return rcu_segcblist head pointer.  Longer term, the
- * rcu_segcblist will be used more pervasively, removing the need for this
- * function.
- */
-static inline struct rcu_head *rcu_segcblist_head(struct rcu_segcblist *rsclp)
-{
-	return rsclp->head;
-}
-
-/*
- * Interim function to return rcu_segcblist head pointer.  Longer term, the
- * rcu_segcblist will be used more pervasively, removing the need for this
- * function.
- */
-static inline struct rcu_head **rcu_segcblist_tail(struct rcu_segcblist *rsclp)
-{
-	WARN_ON_ONCE(rcu_segcblist_empty(rsclp));
-	return rsclp->tails[RCU_NEXT_TAIL];
-}
-
 void rcu_segcblist_init(struct rcu_segcblist *rsclp);
 void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
 bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);

kernel/rcu/rcuperf.c

@@ -89,7 +89,7 @@ torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable
 
 static char *perf_type = "rcu";
 module_param(perf_type, charp, 0444);
-MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, rcu_bh, ...)");
+MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, srcu, ...)");
 
 static int nrealreaders;
 static int nrealwriters;
@@ -375,6 +375,14 @@ rcu_perf_writer(void *arg)
 	if (holdoff)
 		schedule_timeout_uninterruptible(holdoff * HZ);
 
+	/*
+	 * Wait until rcu_end_inkernel_boot() is called for normal GP tests
+	 * so that RCU is not always expedited for normal GP tests.
+	 * The system_state test is approximate, but works well in practice.
+	 */
+	while (!gp_exp && system_state != SYSTEM_RUNNING)
+		schedule_timeout_uninterruptible(1);
+
 	t = ktime_get_mono_fast_ns();
 	if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {
 		t_rcu_perf_writer_started = t;

kernel/rcu/rcutorture.c

@@ -161,6 +161,7 @@ static atomic_long_t n_rcu_torture_timers;
 static long n_barrier_attempts;
 static long n_barrier_successes; /* did rcu_barrier test succeed? */
 static struct list_head rcu_torture_removed;
+static unsigned long shutdown_jiffies;
 
 static int rcu_torture_writer_state;
 #define RTWS_FIXED_DELAY	0
@@ -228,6 +229,15 @@ static u64 notrace rcu_trace_clock_local(void)
 }
 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 
+/*
+ * Stop aggressive CPU-hog tests a bit before the end of the test in order
+ * to avoid interfering with test shutdown.
+ */
+static bool shutdown_time_arrived(void)
+{
+	return shutdown_secs && time_after(jiffies, shutdown_jiffies - 30 * HZ);
+}
+
 static unsigned long boost_starttime;	/* jiffies of next boost test start. */
 static DEFINE_MUTEX(boost_mutex);	/* protect setting boost_starttime */
 					/*  and boost task create/destroy. */
@@ -1713,12 +1723,14 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
 }
 
 // Give the scheduler a chance, even on nohz_full CPUs.
-static void rcu_torture_fwd_prog_cond_resched(void)
+static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)
 {
 	if (IS_ENABLED(CONFIG_PREEMPT) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
-		if (need_resched())
+		// Real call_rcu() floods hit userspace, so emulate that.
+		if (need_resched() || (iter & 0xfff))
 			schedule();
 	} else {
+		// No userspace emulation: CB invocation throttles call_rcu()
 		cond_resched();
 	}
 }
@@ -1746,7 +1758,7 @@ static unsigned long rcu_torture_fwd_prog_cbfree(void)
 		spin_unlock_irqrestore(&rcu_fwd_lock, flags);
 		kfree(rfcp);
 		freed++;
-		rcu_torture_fwd_prog_cond_resched();
+		rcu_torture_fwd_prog_cond_resched(freed);
 	}
 	return freed;
 }
@@ -1785,15 +1797,17 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
 	WRITE_ONCE(rcu_fwd_startat, jiffies);
 	stopat = rcu_fwd_startat + dur;
 	while (time_before(jiffies, stopat) &&
+	       !shutdown_time_arrived() &&
 	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
 		idx = cur_ops->readlock();
 		udelay(10);
 		cur_ops->readunlock(idx);
 		if (!fwd_progress_need_resched || need_resched())
-			rcu_torture_fwd_prog_cond_resched();
+			rcu_torture_fwd_prog_cond_resched(1);
 	}
 	(*tested_tries)++;
 	if (!time_before(jiffies, stopat) &&
+	    !shutdown_time_arrived() &&
 	    !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
 		(*tested)++;
 		cver = READ_ONCE(rcu_torture_current_version) - cver;
@@ -1852,6 +1866,7 @@ static void rcu_torture_fwd_prog_cr(void)
 	gps = cur_ops->get_gp_seq();
 	rcu_launder_gp_seq_start = gps;
 	while (time_before(jiffies, stopat) &&
+	       !shutdown_time_arrived() &&
 	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
 		rfcp = READ_ONCE(rcu_fwd_cb_head);
 		rfcpn = NULL;
@@ -1875,7 +1890,7 @@ static void rcu_torture_fwd_prog_cr(void)
 			rfcp->rfc_gps = 0;
 		}
 		cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
-		rcu_torture_fwd_prog_cond_resched();
+		rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
 	}
 	stoppedat = jiffies;
 	n_launders_cb_snap = READ_ONCE(n_launders_cb);
@@ -1884,7 +1899,8 @@ static void rcu_torture_fwd_prog_cr(void)
 	cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
 	(void)rcu_torture_fwd_prog_cbfree();
 
-	if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop)) {
+	if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop) &&
+	    !shutdown_time_arrived()) {
 		WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
 		pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n",
 			 __func__,
@@ -2465,6 +2481,7 @@ rcu_torture_init(void)
 			goto unwind;
 		rcutor_hp = firsterr;
 	}
+	shutdown_jiffies = jiffies + shutdown_secs * HZ;
 	firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
 	if (firsterr)
 		goto unwind;

kernel/rcu/srcutree.c

@@ -1279,8 +1279,9 @@ void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
 
 		c0 = l0 - u0;
 		c1 = l1 - u1;
-		pr_cont(" %d(%ld,%ld %1p)",
-			cpu, c0, c1, rcu_segcblist_head(&sdp->srcu_cblist));
+		pr_cont(" %d(%ld,%ld %c)",
+			cpu, c0, c1,
+			"C."[rcu_segcblist_empty(&sdp->srcu_cblist)]);
 		s0 += c0;
 		s1 += c1;
 	}

kernel/rcu/tree_exp.h

@@ -781,7 +781,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
  * other hand, if the CPU is not in an RCU read-side critical section,
  * the IPI handler reports the quiescent state immediately.
  *
- * Although this is a greate improvement over previous expedited
+ * Although this is a great improvement over previous expedited
  * implementations, it is still unfriendly to real-time workloads, so is
  * thus not recommended for any sort of common-case code.  In fact, if
  * you are using synchronize_rcu_expedited() in a loop, please restructure
@@ -792,6 +792,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
  */
 void synchronize_rcu_expedited(void)
 {
+	bool boottime = (rcu_scheduler_active == RCU_SCHEDULER_INIT);
 	struct rcu_exp_work rew;
 	struct rcu_node *rnp;
 	unsigned long s;
@@ -817,7 +818,7 @@ void synchronize_rcu_expedited(void)
 		return;  /* Someone else did our work for us. */
 
 	/* Ensure that load happens before action based on it. */
-	if (unlikely(rcu_scheduler_active == RCU_SCHEDULER_INIT)) {
+	if (unlikely(boottime)) {
 		/* Direct call during scheduler init and early_initcalls(). */
 		rcu_exp_sel_wait_wake(s);
 	} else {
@@ -835,5 +836,8 @@ void synchronize_rcu_expedited(void)
 
 	/* Let the next expedited grace period start. */
 	mutex_unlock(&rcu_state.exp_mutex);
+
+	if (likely(!boottime))
+		destroy_work_on_stack(&rew.rew_work);
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);

kernel/rcu/tree_plugin.h

@@ -288,7 +288,6 @@ void rcu_note_context_switch(bool preempt)
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 	struct rcu_node *rnp;
 
-	barrier(); /* Avoid RCU read-side critical sections leaking down. */
 	trace_rcu_utilization(TPS("Start context switch"));
 	lockdep_assert_irqs_disabled();
 	WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0);
@@ -331,7 +330,6 @@ void rcu_note_context_switch(bool preempt)
 	if (rdp->exp_deferred_qs)
 		rcu_report_exp_rdp(rdp);
 	trace_rcu_utilization(TPS("End context switch"));
-	barrier(); /* Avoid RCU read-side critical sections leaking up. */
 }
 EXPORT_SYMBOL_GPL(rcu_note_context_switch);
 
@@ -815,11 +813,6 @@ static void rcu_qs(void)
  * dyntick-idle quiescent state visible to other CPUs, which will in
  * some cases serve for expedited as well as normal grace periods.
  * Either way, register a lightweight quiescent state.
- *
- * The barrier() calls are redundant in the common case when this is
- * called externally, but just in case this is called from within this
- * file.
- *
  */
 void rcu_all_qs(void)
 {
@@ -834,14 +827,12 @@ void rcu_all_qs(void)
 		return;
 	}
 	this_cpu_write(rcu_data.rcu_urgent_qs, false);
-	barrier(); /* Avoid RCU read-side critical sections leaking down. */
 	if (unlikely(raw_cpu_read(rcu_data.rcu_need_heavy_qs))) {
 		local_irq_save(flags);
 		rcu_momentary_dyntick_idle();
 		local_irq_restore(flags);
 	}
 	rcu_qs();
-	barrier(); /* Avoid RCU read-side critical sections leaking up. */
 	preempt_enable();
 }
 EXPORT_SYMBOL_GPL(rcu_all_qs);
@@ -851,7 +842,6 @@ EXPORT_SYMBOL_GPL(rcu_all_qs);
  */
 void rcu_note_context_switch(bool preempt)
 {
-	barrier(); /* Avoid RCU read-side critical sections leaking down. */
 	trace_rcu_utilization(TPS("Start context switch"));
 	rcu_qs();
 	/* Load rcu_urgent_qs before other flags. */
@@ -864,7 +854,6 @@ void rcu_note_context_switch(bool preempt)
 		rcu_tasks_qs(current);
 out:
 	trace_rcu_utilization(TPS("End context switch"));
-	barrier(); /* Avoid RCU read-side critical sections leaking up. */
 }
 EXPORT_SYMBOL_GPL(rcu_note_context_switch);
 
@@ -1121,7 +1110,7 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
  * already exist.  We only create this kthread for preemptible RCU.
  * Returns zero if all is well, a negated errno otherwise.
  */
-static int rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
+static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
 {
 	int rnp_index = rnp - rcu_get_root();
 	unsigned long flags;
@@ -1129,25 +1118,27 @@ static int rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
 	struct task_struct *t;
 
 	if (!IS_ENABLED(CONFIG_PREEMPT_RCU))
-		return 0;
+		return;
 
 	if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0)
-		return 0;
+		return;
 
 	rcu_state.boost = 1;
+
 	if (rnp->boost_kthread_task != NULL)
-		return 0;
+		return;
+
 	t = kthread_create(rcu_boost_kthread, (void *)rnp,
 			   "rcub/%d", rnp_index);
-	if (IS_ERR(t))
-		return PTR_ERR(t);
+	if (WARN_ON_ONCE(IS_ERR(t)))
+		return;
+
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
 	rnp->boost_kthread_task = t;
 	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	sp.sched_priority = kthread_prio;
 	sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
 	wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
-	return 0;
 }
 
 /*
@@ -1188,7 +1179,7 @@ static void __init rcu_spawn_boost_kthreads(void)
 	struct rcu_node *rnp;
 
 	rcu_for_each_leaf_node(rnp)
-		(void)rcu_spawn_one_boost_kthread(rnp);
+		rcu_spawn_one_boost_kthread(rnp);
 }
 
 static void rcu_prepare_kthreads(int cpu)
@@ -1198,7 +1189,7 @@ static void rcu_prepare_kthreads(int cpu)
 
 	/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
 	if (rcu_scheduler_fully_active)
-		(void)rcu_spawn_one_boost_kthread(rnp);
+		rcu_spawn_one_boost_kthread(rnp);
 }
 
 #else /* #ifdef CONFIG_RCU_BOOST */

kernel/rcu/tree_stall.h

@@ -527,6 +527,8 @@ static void check_cpu_stall(struct rcu_data *rdp)
 
 		/* We haven't checked in, so go dump stack. */
 		print_cpu_stall();
+		if (rcu_cpu_stall_ftrace_dump)
+			rcu_ftrace_dump(DUMP_ALL);
 
 	} else if (rcu_gp_in_progress() &&
 		   ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) &&
@@ -534,6 +536,8 @@ static void check_cpu_stall(struct rcu_data *rdp)
 
 		/* They had a few time units to dump stack, so complain. */
 		print_other_cpu_stall(gs2);
+		if (rcu_cpu_stall_ftrace_dump)
+			rcu_ftrace_dump(DUMP_ALL);
 	}
 }
 

kernel/rcu/update.c

@@ -61,9 +61,15 @@ module_param(rcu_normal_after_boot, int, 0);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 /**
- * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
+ * rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section?
+ * @ret:	Best guess answer if lockdep cannot be relied on
  *
- * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an
+ * Returns true if lockdep must be ignored, in which case *ret contains
+ * the best guess described below.  Otherwise returns false, in which
+ * case *ret tells the caller nothing and the caller should instead
+ * consult lockdep.
+ *
+ * If CONFIG_DEBUG_LOCK_ALLOC is selected, set *ret to nonzero iff in an
  * RCU-sched read-side critical section.  In absence of
  * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
  * critical section unless it can prove otherwise.  Note that disabling
@@ -75,35 +81,45 @@ module_param(rcu_normal_after_boot, int, 0);
  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot
  * and while lockdep is disabled.
  *
- * Note that if the CPU is in the idle loop from an RCU point of
- * view (ie: that we are in the section between rcu_idle_enter() and
- * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU
- * did an rcu_read_lock().  The reason for this is that RCU ignores CPUs
- * that are in such a section, considering these as in extended quiescent
- * state, so such a CPU is effectively never in an RCU read-side critical
- * section regardless of what RCU primitives it invokes.  This state of
- * affairs is required --- 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.
+ * Note that if the CPU is in the idle loop from an RCU point of view (ie:
+ * that we are in the section between rcu_idle_enter() and rcu_idle_exit())
+ * then rcu_read_lock_held() sets *ret to false even if the CPU did an
+ * rcu_read_lock().  The reason for this is that RCU ignores CPUs that are
+ * in such a section, considering these as in extended quiescent state,
+ * so such a CPU is effectively never in an RCU read-side critical section
+ * regardless of what RCU primitives it invokes.  This state of affairs is
+ * required --- 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.
  *
- * Similarly, we avoid claiming an SRCU read lock held if the current
+ * Similarly, we avoid claiming an RCU read lock held if the current
  * CPU is offline.
  */
+static bool rcu_read_lock_held_common(bool *ret)
+{
+	if (!debug_lockdep_rcu_enabled()) {
+		*ret = 1;
+		return true;
+	}
+	if (!rcu_is_watching()) {
+		*ret = 0;
+		return true;
+	}
+	if (!rcu_lockdep_current_cpu_online()) {
+		*ret = 0;
+		return true;
+	}
+	return false;
+}
+
 int rcu_read_lock_sched_held(void)
 {
-	int lockdep_opinion = 0;
+	bool ret;
 
-	if (!debug_lockdep_rcu_enabled())
-		return 1;
-	if (!rcu_is_watching())
-		return 0;
-	if (!rcu_lockdep_current_cpu_online())
-		return 0;
-	if (debug_locks)
-		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
-	return lockdep_opinion || !preemptible();
+	if (rcu_read_lock_held_common(&ret))
+		return ret;
+	return lock_is_held(&rcu_sched_lock_map) || !preemptible();
 }
 EXPORT_SYMBOL(rcu_read_lock_sched_held);
 #endif
@@ -136,8 +152,7 @@ static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1);
  */
 bool rcu_gp_is_expedited(void)
 {
-	return rcu_expedited || atomic_read(&rcu_expedited_nesting) ||
-	       rcu_scheduler_active == RCU_SCHEDULER_INIT;
+	return rcu_expedited || atomic_read(&rcu_expedited_nesting);
 }
 EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
 
@@ -261,12 +276,10 @@ NOKPROBE_SYMBOL(debug_lockdep_rcu_enabled);
  */
 int rcu_read_lock_held(void)
 {
-	if (!debug_lockdep_rcu_enabled())
-		return 1;
-	if (!rcu_is_watching())
-		return 0;
-	if (!rcu_lockdep_current_cpu_online())
-		return 0;
+	bool ret;
+
+	if (rcu_read_lock_held_common(&ret))
+		return ret;
 	return lock_is_held(&rcu_lock_map);
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_held);
@@ -288,16 +301,28 @@ EXPORT_SYMBOL_GPL(rcu_read_lock_held);
  */
 int rcu_read_lock_bh_held(void)
 {
-	if (!debug_lockdep_rcu_enabled())
-		return 1;
-	if (!rcu_is_watching())
-		return 0;
-	if (!rcu_lockdep_current_cpu_online())
-		return 0;
+	bool ret;
+
+	if (rcu_read_lock_held_common(&ret))
+		return ret;
 	return in_softirq() || irqs_disabled();
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
 
+int rcu_read_lock_any_held(void)
+{
+	bool ret;
+
+	if (rcu_read_lock_held_common(&ret))
+		return ret;
+	if (lock_is_held(&rcu_lock_map) ||
+	    lock_is_held(&rcu_bh_lock_map) ||
+	    lock_is_held(&rcu_sched_lock_map))
+		return 1;
+	return !preemptible();
+}
+EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);
+
 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 /**
@@ -437,6 +462,8 @@ EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity);
 #endif
 
 #ifdef CONFIG_RCU_STALL_COMMON
+int rcu_cpu_stall_ftrace_dump __read_mostly;
+module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
 int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
 module_param(rcu_cpu_stall_suppress, int, 0644);