Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits)
  cpu: Export cpu_up()
  rcu: Apply ACCESS_ONCE() to rcu_boost() return value
  Revert "rcu: Permit rt_mutex_unlock() with irqs disabled"
  docs: Additional LWN links to RCU API
  rcu: Augment rcu_batch_end tracing for idle and callback state
  rcu: Add rcutorture tests for srcu_read_lock_raw()
  rcu: Make rcutorture test for hotpluggability before offlining CPUs
  driver-core/cpu: Expose hotpluggability to the rest of the kernel
  rcu: Remove redundant rcu_cpu_stall_suppress declaration
  rcu: Adaptive dyntick-idle preparation
  rcu: Keep invoking callbacks if CPU otherwise idle
  rcu: Irq nesting is always 0 on rcu_enter_idle_common
  rcu: Don't check irq nesting from rcu idle entry/exit
  rcu: Permit dyntick-idle with callbacks pending
  rcu: Document same-context read-side constraints
  rcu: Identify dyntick-idle CPUs on first force_quiescent_state() pass
  rcu: Remove dynticks false positives and RCU failures
  rcu: Reduce latency of rcu_prepare_for_idle()
  rcu: Eliminate RCU_FAST_NO_HZ grace-period hang
  rcu: Avoid needlessly IPIing CPUs at GP end
  ...

17 files changed, 933 insertions, 243 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 563f1360947..9d448ddb224 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -380,6 +380,7 @@ out:
 	cpu_maps_update_done();
 	return err;
 }
+EXPORT_SYMBOL_GPL(cpu_up);
 
 #ifdef CONFIG_PM_SLEEP_SMP
 static cpumask_var_t frozen_cpus;
diff --git a/kernel/debug/kdb/kdb_support.c b/kernel/debug/kdb/kdb_support.c
index 5532dd37aa8..7d6fb40d218 100644
--- a/kernel/debug/kdb/kdb_support.c
+++ b/kernel/debug/kdb/kdb_support.c
@@ -636,7 +636,7 @@ char kdb_task_state_char (const struct task_struct *p)
 		(p->exit_state & EXIT_ZOMBIE) ? 'Z' :
 		(p->exit_state & EXIT_DEAD) ? 'E' :
 		(p->state & TASK_INTERRUPTIBLE) ? 'S' : '?';
-	if (p->pid == 0) {
+	if (is_idle_task(p)) {
 		/* Idle task.  Is it really idle, apart from the kdb
 		 * interrupt? */
 		if (!kdb_task_has_cpu(p) || kgdb_info[cpu].irq_depth == 1) {
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 58690af323e..fc0e7ff11dd 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5366,7 +5366,7 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
 	regs = get_irq_regs();
 
 	if (regs && !perf_exclude_event(event, regs)) {
-		if (!(event->attr.exclude_idle && current->pid == 0))
+		if (!(event->attr.exclude_idle && is_idle_task(current)))
 			if (perf_event_overflow(event, &data, regs))
 				ret = HRTIMER_NORESTART;
 	}
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index e69d633d6aa..8fb75513232 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -4181,6 +4181,28 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
 	printk("%s:%d %s!\n", file, line, s);
 	printk("\nother info that might help us debug this:\n\n");
 	printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
+
+	/*
+	 * If a CPU is in the RCU-free window in idle (ie: in the section
+	 * between rcu_idle_enter() and rcu_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_cpu_idle())
+		printk("RCU used illegally from extended quiescent state!\n");
+
 	lockdep_print_held_locks(curr);
 	printk("\nstack backtrace:\n");
 	dump_stack();
diff --git a/kernel/rcu.h b/kernel/rcu.h
index f600868d550..aa88baab5f7 100644
--- a/kernel/rcu.h
+++ b/kernel/rcu.h
@@ -30,6 +30,13 @@
 #endif /* #else #ifdef CONFIG_RCU_TRACE */
 
 /*
+ * Process-level increment to ->dynticks_nesting field.  This allows for
+ * architectures that use half-interrupts and half-exceptions from
+ * process context.
+ */
+#define DYNTICK_TASK_NESTING (LLONG_MAX / 2 - 1)
+
+/*
  * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
  * by call_rcu() and rcu callback execution, and are therefore not part of the
  * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index c5b98e565ae..2bc4e135ff2 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -93,6 +93,8 @@ int rcu_read_lock_bh_held(void)
 {
 	if (!debug_lockdep_rcu_enabled())
 		return 1;
+	if (rcu_is_cpu_idle())
+		return 0;
 	return in_softirq() || irqs_disabled();
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
@@ -316,3 +318,13 @@ struct debug_obj_descr rcuhead_debug_descr = {
 };
 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
+void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp)
+{
+	trace_rcu_torture_read(rcutorturename, rhp);
+}
+EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
+#else
+#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
+#endif
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 636af6d9c6e..977296dca0a 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -53,31 +53,137 @@ static void __call_rcu(struct rcu_head *head,
 
 #include "rcutiny_plugin.h"
 
-#ifdef CONFIG_NO_HZ
+static long long rcu_dynticks_nesting = DYNTICK_TASK_NESTING;
 
-static long rcu_dynticks_nesting = 1;
+/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
+static void rcu_idle_enter_common(long long oldval)
+{
+	if (rcu_dynticks_nesting) {
+		RCU_TRACE(trace_rcu_dyntick("--=",
+					    oldval, rcu_dynticks_nesting));
+		return;
+	}
+	RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
+	if (!is_idle_task(current)) {
+		struct task_struct *idle = idle_task(smp_processor_id());
+
+		RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
+					    oldval, rcu_dynticks_nesting));
+		ftrace_dump(DUMP_ALL);
+		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+			  current->pid, current->comm,
+			  idle->pid, idle->comm); /* must be idle task! */
+	}
+	rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+}
 
 /*
- * Enter dynticks-idle mode, which is an extended quiescent state
- * if we have fully entered that mode (i.e., if the new value of
- * dynticks_nesting is zero).
+ * Enter idle, which is an extended quiescent state if we have fully
+ * entered that mode (i.e., if the new value of dynticks_nesting is zero).
  */
-void rcu_enter_nohz(void)
+void rcu_idle_enter(void)
 {
-	if (--rcu_dynticks_nesting == 0)
-		rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+	unsigned long flags;
+	long long oldval;
+
+	local_irq_save(flags);
+	oldval = rcu_dynticks_nesting;
+	rcu_dynticks_nesting = 0;
+	rcu_idle_enter_common(oldval);
+	local_irq_restore(flags);
 }
 
 /*
- * Exit dynticks-idle mode, so that we are no longer in an extended
- * quiescent state.
+ * Exit an interrupt handler towards idle.
  */
-void rcu_exit_nohz(void)
+void rcu_irq_exit(void)
+{
+	unsigned long flags;
+	long long oldval;
+
+	local_irq_save(flags);
+	oldval = rcu_dynticks_nesting;
+	rcu_dynticks_nesting--;
+	WARN_ON_ONCE(rcu_dynticks_nesting < 0);
+	rcu_idle_enter_common(oldval);
+	local_irq_restore(flags);
+}
+
+/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
+static void rcu_idle_exit_common(long long oldval)
 {
+	if (oldval) {
+		RCU_TRACE(trace_rcu_dyntick("++=",
+					    oldval, rcu_dynticks_nesting));
+		return;
+	}
+	RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
+	if (!is_idle_task(current)) {
+		struct task_struct *idle = idle_task(smp_processor_id());
+
+		RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
+			  oldval, rcu_dynticks_nesting));
+		ftrace_dump(DUMP_ALL);
+		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+			  current->pid, current->comm,
+			  idle->pid, idle->comm); /* must be idle task! */
+	}
+}
+
+/*
+ * Exit idle, so that we are no longer in an extended quiescent state.
+ */
+void rcu_idle_exit(void)
+{
+	unsigned long flags;
+	long long oldval;
+
+	local_irq_save(flags);
+	oldval = rcu_dynticks_nesting;
+	WARN_ON_ONCE(oldval != 0);
+	rcu_dynticks_nesting = DYNTICK_TASK_NESTING;
+	rcu_idle_exit_common(oldval);
+	local_irq_restore(flags);
+}
+
+/*
+ * Enter an interrupt handler, moving away from idle.
+ */
+void rcu_irq_enter(void)
+{
+	unsigned long flags;
+	long long oldval;
+
+	local_irq_save(flags);
+	oldval = rcu_dynticks_nesting;
 	rcu_dynticks_nesting++;
+	WARN_ON_ONCE(rcu_dynticks_nesting == 0);
+	rcu_idle_exit_common(oldval);
+	local_irq_restore(flags);
+}
+
+#ifdef CONFIG_PROVE_RCU
+
+/*
+ * Test whether RCU thinks that the current CPU is idle.
+ */
+int rcu_is_cpu_idle(void)
+{
+	return !rcu_dynticks_nesting;
 }
+EXPORT_SYMBOL(rcu_is_cpu_idle);
+
+#endif /* #ifdef CONFIG_PROVE_RCU */
 
-#endif /* #ifdef CONFIG_NO_HZ */
+/*
+ * Test whether the current CPU was interrupted from idle.  Nested
+ * interrupts don't count, we must be running at the first interrupt
+ * level.
+ */
+int rcu_is_cpu_rrupt_from_idle(void)
+{
+	return rcu_dynticks_nesting <= 0;
+}
 
 /*
  * Helper function for rcu_sched_qs() and rcu_bh_qs().
@@ -126,14 +232,13 @@ void rcu_bh_qs(int cpu)
 
 /*
  * Check to see if the scheduling-clock interrupt came from an extended
- * quiescent state, and, if so, tell RCU about it.
+ * quiescent state, and, if so, tell RCU about it.  This function must
+ * be called from hardirq context.  It is normally called from the
+ * scheduling-clock interrupt.
  */
 void rcu_check_callbacks(int cpu, int user)
 {
-	if (user ||
-	    (idle_cpu(cpu) &&
-	     !in_softirq() &&
-	     hardirq_count() <= (1 << HARDIRQ_SHIFT)))
+	if (user || rcu_is_cpu_rrupt_from_idle())
 		rcu_sched_qs(cpu);
 	else if (!in_softirq())
 		rcu_bh_qs(cpu);
@@ -154,7 +259,11 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 	/* If no RCU callbacks ready to invoke, just return. */
 	if (&rcp->rcucblist == rcp->donetail) {
 		RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1));
-		RCU_TRACE(trace_rcu_batch_end(rcp->name, 0));
+		RCU_TRACE(trace_rcu_batch_end(rcp->name, 0,
+					      ACCESS_ONCE(rcp->rcucblist),
+					      need_resched(),
+					      is_idle_task(current),
+					      rcu_is_callbacks_kthread()));
 		return;
 	}
 
@@ -183,7 +292,9 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 		RCU_TRACE(cb_count++);
 	}
 	RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
-	RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count));
+	RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count, 0, need_resched(),
+				      is_idle_task(current),
+				      rcu_is_callbacks_kthread()));
 }
 
 static void rcu_process_callbacks(struct softirq_action *unused)
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 2b0484a5dc2..9cb1ae4aabd 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -312,8 +312,8 @@ static int rcu_boost(void)
 	rt_mutex_lock(&mtx);
 	rt_mutex_unlock(&mtx);  /* Keep lockdep happy. */
 
-	return rcu_preempt_ctrlblk.boost_tasks != NULL ||
-	       rcu_preempt_ctrlblk.exp_tasks != NULL;
+	return ACCESS_ONCE(rcu_preempt_ctrlblk.boost_tasks) != NULL ||
+	       ACCESS_ONCE(rcu_preempt_ctrlblk.exp_tasks) != NULL;
 }
 
 /*
@@ -885,6 +885,19 @@ static void invoke_rcu_callbacks(void)
 	wake_up(&rcu_kthread_wq);
 }
 
+#ifdef CONFIG_RCU_TRACE
+
+/*
+ * Is the current CPU running the RCU-callbacks kthread?
+ * Caller must have preemption disabled.
+ */
+static bool rcu_is_callbacks_kthread(void)
+{
+	return rcu_kthread_task == current;
+}
+
+#endif /* #ifdef CONFIG_RCU_TRACE */
+
 /*
  * This kthread invokes RCU callbacks whose grace periods have
  * elapsed.  It is awakened as needed, and takes the place of the
@@ -938,6 +951,18 @@ void invoke_rcu_callbacks(void)
 	raise_softirq(RCU_SOFTIRQ);
 }
 
+#ifdef CONFIG_RCU_TRACE
+
+/*
+ * There is no callback kthread, so this thread is never it.
+ */
+static bool rcu_is_callbacks_kthread(void)
+{
+	return false;
+}
+
+#endif /* #ifdef CONFIG_RCU_TRACE */
+
 void rcu_init(void)
 {
 	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 764825c2685..88f17b8a3b1 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -61,9 +61,11 @@ static int test_no_idle_hz;	/* Test RCU's support for tickless idle CPUs. */
 static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
 static int stutter = 5;		/* Start/stop testing interval (in sec) */
 static int irqreader = 1;	/* RCU readers from irq (timers). */
-static int fqs_duration = 0;	/* Duration of bursts (us), 0 to disable. */
-static int fqs_holdoff = 0;	/* Hold time within burst (us). */
+static int fqs_duration;	/* Duration of bursts (us), 0 to disable. */
+static int fqs_holdoff;		/* Hold time within burst (us). */
 static int fqs_stutter = 3;	/* Wait time between bursts (s). */
+static int onoff_interval;	/* Wait time between CPU hotplugs, 0=disable. */
+static int shutdown_secs;	/* Shutdown time (s).  <=0 for no shutdown. */
 static int test_boost = 1;	/* Test RCU prio boost: 0=no, 1=maybe, 2=yes. */
 static int test_boost_interval = 7; /* Interval between boost tests, seconds. */
 static int test_boost_duration = 4; /* Duration of each boost test, seconds. */
@@ -91,6 +93,10 @@ module_param(fqs_holdoff, int, 0444);
 MODULE_PARM_DESC(fqs_holdoff, "Holdoff time within fqs bursts (us)");
 module_param(fqs_stutter, int, 0444);
 MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
+module_param(onoff_interval, int, 0444);
+MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
+module_param(shutdown_secs, int, 0444);
+MODULE_PARM_DESC(shutdown_secs, "Shutdown time (s), zero to disable.");
 module_param(test_boost, int, 0444);
 MODULE_PARM_DESC(test_boost, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
 module_param(test_boost_interval, int, 0444);
@@ -119,6 +125,10 @@ static struct task_struct *shuffler_task;
 static struct task_struct *stutter_task;
 static struct task_struct *fqs_task;
 static struct task_struct *boost_tasks[NR_CPUS];
+static struct task_struct *shutdown_task;
+#ifdef CONFIG_HOTPLUG_CPU
+static struct task_struct *onoff_task;
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
 
 #define RCU_TORTURE_PIPE_LEN 10
 
@@ -149,6 +159,10 @@ static long n_rcu_torture_boost_rterror;
 static long n_rcu_torture_boost_failure;
 static long n_rcu_torture_boosts;
 static long n_rcu_torture_timers;
+static long n_offline_attempts;
+static long n_offline_successes;
+static long n_online_attempts;
+static long n_online_successes;
 static struct list_head rcu_torture_removed;
 static cpumask_var_t shuffle_tmp_mask;
 
@@ -160,6 +174,8 @@ static int stutter_pause_test;
 #define RCUTORTURE_RUNNABLE_INIT 0
 #endif
 int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
+module_param(rcutorture_runnable, int, 0444);
+MODULE_PARM_DESC(rcutorture_runnable, "Start rcutorture at boot");
 
 #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU)
 #define rcu_can_boost() 1
@@ -167,6 +183,7 @@ int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
 #define rcu_can_boost() 0
 #endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
 
+static unsigned long shutdown_time;	/* jiffies to system shutdown. */
 static unsigned long boost_starttime;	/* jiffies of next boost test start. */
 DEFINE_MUTEX(boost_mutex);		/* protect setting boost_starttime */
 					/*  and boost task create/destroy. */
@@ -182,6 +199,9 @@ static int fullstop = FULLSTOP_RMMOD;
  */
 static DEFINE_MUTEX(fullstop_mutex);
 
+/* Forward reference. */
+static void rcu_torture_cleanup(void);
+
 /*
  * Detect and respond to a system shutdown.
  */
@@ -612,6 +632,30 @@ static struct rcu_torture_ops srcu_ops = {
 	.name		= "srcu"
 };
 
+static int srcu_torture_read_lock_raw(void) __acquires(&srcu_ctl)
+{
+	return srcu_read_lock_raw(&srcu_ctl);
+}
+
+static void srcu_torture_read_unlock_raw(int idx) __releases(&srcu_ctl)
+{
+	srcu_read_unlock_raw(&srcu_ctl, idx);
+}
+
+static struct rcu_torture_ops srcu_raw_ops = {
+	.init		= srcu_torture_init,
+	.cleanup	= srcu_torture_cleanup,
+	.readlock	= srcu_torture_read_lock_raw,
+	.read_delay	= srcu_read_delay,
+	.readunlock	= srcu_torture_read_unlock_raw,
+	.completed	= srcu_torture_completed,
+	.deferred_free	= rcu_sync_torture_deferred_free,
+	.sync		= srcu_torture_synchronize,
+	.cb_barrier	= NULL,
+	.stats		= srcu_torture_stats,
+	.name		= "srcu_raw"
+};
+
 static void srcu_torture_synchronize_expedited(void)
 {
 	synchronize_srcu_expedited(&srcu_ctl);
@@ -913,6 +957,18 @@ rcu_torture_fakewriter(void *arg)
 	return 0;
 }
 
+void rcutorture_trace_dump(void)
+{
+	static atomic_t beenhere = ATOMIC_INIT(0);
+
+	if (atomic_read(&beenhere))
+		return;
+	if (atomic_xchg(&beenhere, 1) != 0)
+		return;
+	do_trace_rcu_torture_read(cur_ops->name, (struct rcu_head *)~0UL);
+	ftrace_dump(DUMP_ALL);
+}
+
 /*
  * RCU torture reader from timer handler.  Dereferences rcu_torture_current,
  * incrementing the corresponding element of the pipeline array.  The
@@ -934,6 +990,7 @@ static void rcu_torture_timer(unsigned long unused)
 				  rcu_read_lock_bh_held() ||
 				  rcu_read_lock_sched_held() ||
 				  srcu_read_lock_held(&srcu_ctl));
+	do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 	if (p == NULL) {
 		/* Leave because rcu_torture_writer is not yet underway */
 		cur_ops->readunlock(idx);
@@ -951,6 +1008,8 @@ static void rcu_torture_timer(unsigned long unused)
 		/* Should not happen, but... */
 		pipe_count = RCU_TORTURE_PIPE_LEN;
 	}
+	if (pipe_count > 1)
+		rcutorture_trace_dump();
 	__this_cpu_inc(rcu_torture_count[pipe_count]);
 	completed = cur_ops->completed() - completed;
 	if (completed > RCU_TORTURE_PIPE_LEN) {
@@ -994,6 +1053,7 @@ rcu_torture_reader(void *arg)
 					  rcu_read_lock_bh_held() ||
 					  rcu_read_lock_sched_held() ||
 					  srcu_read_lock_held(&srcu_ctl));
+		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 		if (p == NULL) {
 			/* Wait for rcu_torture_writer to get underway */
 			cur_ops->readunlock(idx);
@@ -1009,6 +1069,8 @@ rcu_torture_reader(void *arg)
 			/* Should not happen, but... */
 			pipe_count = RCU_TORTURE_PIPE_LEN;
 		}
+		if (pipe_count > 1)
+			rcutorture_trace_dump();
 		__this_cpu_inc(rcu_torture_count[pipe_count]);
 		completed = cur_ops->completed() - completed;
 		if (completed > RCU_TORTURE_PIPE_LEN) {
@@ -1056,7 +1118,8 @@ rcu_torture_printk(char *page)
 	cnt += sprintf(&page[cnt],
 		       "rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d "
 		       "rtmbe: %d rtbke: %ld rtbre: %ld "
-		       "rtbf: %ld rtb: %ld nt: %ld",
+		       "rtbf: %ld rtb: %ld nt: %ld "
+		       "onoff: %ld/%ld:%ld/%ld",
 		       rcu_torture_current,
 		       rcu_torture_current_version,
 		       list_empty(&rcu_torture_freelist),
@@ -1068,7 +1131,11 @@ rcu_torture_printk(char *page)
 		       n_rcu_torture_boost_rterror,
 		       n_rcu_torture_boost_failure,
 		       n_rcu_torture_boosts,
-		       n_rcu_torture_timers);
+		       n_rcu_torture_timers,
+		       n_online_successes,
+		       n_online_attempts,
+		       n_offline_successes,
+		       n_offline_attempts);
 	if (atomic_read(&n_rcu_torture_mberror) != 0 ||
 	    n_rcu_torture_boost_ktrerror != 0 ||
 	    n_rcu_torture_boost_rterror != 0 ||
@@ -1232,12 +1299,14 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
 		"shuffle_interval=%d stutter=%d irqreader=%d "
 		"fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
 		"test_boost=%d/%d test_boost_interval=%d "
-		"test_boost_duration=%d\n",
+		"test_boost_duration=%d shutdown_secs=%d "
+		"onoff_interval=%d\n",
 		torture_type, tag, nrealreaders, nfakewriters,
 		stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 		stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
 		test_boost, cur_ops->can_boost,
-		test_boost_interval, test_boost_duration);
+		test_boost_interval, test_boost_duration, shutdown_secs,
+		onoff_interval);
 }
 
 static struct notifier_block rcutorture_shutdown_nb = {
@@ -1287,6 +1356,131 @@ static int rcutorture_booster_init(int cpu)
 	return 0;
 }
 
+/*
+ * Cause the rcutorture test to shutdown the system after the test has
+ * run for the time specified by the shutdown_secs module parameter.
+ */
+static int
+rcu_torture_shutdown(void *arg)
+{
+	long delta;
+	unsigned long jiffies_snap;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_shutdown task started");
+	jiffies_snap = ACCESS_ONCE(jiffies);
+	while (ULONG_CMP_LT(jiffies_snap, shutdown_time) &&
+	       !kthread_should_stop()) {
+		delta = shutdown_time - jiffies_snap;
+		if (verbose)
+			printk(KERN_ALERT "%s" TORTURE_FLAG
+			       "rcu_torture_shutdown task: %lu "
+			       "jiffies remaining\n",
+			       torture_type, delta);
+		schedule_timeout_interruptible(delta);
+		jiffies_snap = ACCESS_ONCE(jiffies);
+	}
+	if (kthread_should_stop()) {
+		VERBOSE_PRINTK_STRING("rcu_torture_shutdown task stopping");
+		return 0;
+	}
+
+	/* OK, shut down the system. */
+
+	VERBOSE_PRINTK_STRING("rcu_torture_shutdown task shutting down system");
+	shutdown_task = NULL;	/* Avoid self-kill deadlock. */
+	rcu_torture_cleanup();	/* Get the success/failure message. */
+	kernel_power_off();	/* Shut down the system. */
+	return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Execute random CPU-hotplug operations at the interval specified
+ * by the onoff_interval.
+ */
+static int
+rcu_torture_onoff(void *arg)
+{
+	int cpu;
+	int maxcpu = -1;
+	DEFINE_RCU_RANDOM(rand);
+
+	VERBOSE_PRINTK_STRING("rcu_torture_onoff task started");
+	for_each_online_cpu(cpu)
+		maxcpu = cpu;
+	WARN_ON(maxcpu < 0);
+	while (!kthread_should_stop()) {
+		cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1);
+		if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {
+			if (verbose)
+				printk(KERN_ALERT "%s" TORTURE_FLAG
+				       "rcu_torture_onoff task: offlining %d\n",
+				       torture_type, cpu);
+			n_offline_attempts++;
+			if (cpu_down(cpu) == 0) {
+				if (verbose)
+					printk(KERN_ALERT "%s" TORTURE_FLAG
+					       "rcu_torture_onoff task: "
+					       "offlined %d\n",
+					       torture_type, cpu);
+				n_offline_successes++;
+			}
+		} else if (cpu_is_hotpluggable(cpu)) {
+			if (verbose)
+				printk(KERN_ALERT "%s" TORTURE_FLAG
+				       "rcu_torture_onoff task: onlining %d\n",
+				       torture_type, cpu);
+			n_online_attempts++;
+			if (cpu_up(cpu) == 0) {
+				if (verbose)
+					printk(KERN_ALERT "%s" TORTURE_FLAG
+					       "rcu_torture_onoff task: "
+					       "onlined %d\n",
+					       torture_type, cpu);
+				n_online_successes++;
+			}
+		}
+		schedule_timeout_interruptible(onoff_interval * HZ);
+	}
+	VERBOSE_PRINTK_STRING("rcu_torture_onoff task stopping");
+	return 0;
+}
+
+static int
+rcu_torture_onoff_init(void)
+{
+	if (onoff_interval <= 0)
+		return 0;
+	onoff_task = kthread_run(rcu_torture_onoff, NULL, "rcu_torture_onoff");
+	if (IS_ERR(onoff_task)) {
+		onoff_task = NULL;
+		return PTR_ERR(onoff_task);
+	}
+	return 0;
+}
+
+static void rcu_torture_onoff_cleanup(void)
+{
+	if (onoff_task == NULL)
+		return;
+	VERBOSE_PRINTK_STRING("Stopping rcu_torture_onoff task");
+	kthread_stop(onoff_task);
+}
+
+#else /* #ifdef CONFIG_HOTPLUG_CPU */
+
+static void
+rcu_torture_onoff_init(void)
+{
+}
+
+static void rcu_torture_onoff_cleanup(void)
+{
+}
+
+#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
+
 static int rcutorture_cpu_notify(struct notifier_block *self,
 				 unsigned long action, void *hcpu)
 {
@@ -1391,6 +1585,11 @@ rcu_torture_cleanup(void)
 		for_each_possible_cpu(i)
 			rcutorture_booster_cleanup(i);
 	}
+	if (shutdown_task != NULL) {
+		VERBOSE_PRINTK_STRING("Stopping rcu_torture_shutdown task");
+		kthread_stop(shutdown_task);
+	}
+	rcu_torture_onoff_cleanup();
 
 	/* Wait for all RCU callbacks to fire.  */
 
@@ -1416,7 +1615,7 @@ rcu_torture_init(void)
 	static struct rcu_torture_ops *torture_ops[] =
 		{ &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
 		  &rcu_bh_ops, &rcu_bh_sync_ops, &rcu_bh_expedited_ops,
-		  &srcu_ops, &srcu_expedited_ops,
+		  &srcu_ops, &srcu_raw_ops, &srcu_expedited_ops,
 		  &sched_ops, &sched_sync_ops, &sched_expedited_ops, };
 
 	mutex_lock(&fullstop_mutex);
@@ -1607,6 +1806,18 @@ rcu_torture_init(void)
 			}
 		}
 	}
+	if (shutdown_secs > 0) {
+		shutdown_time = jiffies + shutdown_secs * HZ;
+		shutdown_task = kthread_run(rcu_torture_shutdown, NULL,
+					    "rcu_torture_shutdown");
+		if (IS_ERR(shutdown_task)) {
+			firsterr = PTR_ERR(shutdown_task);
+			VERBOSE_PRINTK_ERRSTRING("Failed to create shutdown");
+			shutdown_task = NULL;
+			goto unwind;
+		}
+	}
+	rcu_torture_onoff_init();
 	register_reboot_notifier(&rcutorture_shutdown_nb);
 	rcutorture_record_test_transition();
 	mutex_unlock(&fullstop_mutex);
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 6b76d812740..6c4a6722abf 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -69,7 +69,7 @@ static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
 		NUM_RCU_LVL_3, \
 		NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \
 	}, \
-	.signaled = RCU_GP_IDLE, \
+	.fqs_state = RCU_GP_IDLE, \
 	.gpnum = -300, \
 	.completed = -300, \
 	.onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.onofflock), \
@@ -195,12 +195,10 @@ void rcu_note_context_switch(int cpu)
 }
 EXPORT_SYMBOL_GPL(rcu_note_context_switch);
 
-#ifdef CONFIG_NO_HZ
 DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
-	.dynticks_nesting = 1,
+	.dynticks_nesting = DYNTICK_TASK_NESTING,
 	.dynticks = ATOMIC_INIT(1),
 };
-#endif /* #ifdef CONFIG_NO_HZ */
 
 static int blimit = 10;		/* Maximum callbacks per rcu_do_batch. */
 static int qhimark = 10000;	/* If this many pending, ignore blimit. */
@@ -328,11 +326,11 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
 		return 1;
 	}
 
-	/* If preemptible RCU, no point in sending reschedule IPI. */
-	if (rdp->preemptible)
-		return 0;
-
-	/* The CPU is online, so send it a reschedule IPI. */
+	/*
+	 * The CPU is online, so send it a reschedule IPI.  This forces
+	 * it through the scheduler, and (inefficiently) also handles cases
+	 * where idle loops fail to inform RCU about the CPU being idle.
+	 */
 	if (rdp->cpu != smp_processor_id())
 		smp_send_reschedule(rdp->cpu);
 	else
@@ -343,59 +341,181 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
 
 #endif /* #ifdef CONFIG_SMP */
 
-#ifdef CONFIG_NO_HZ
+/*
+ * rcu_idle_enter_common - inform RCU that current CPU is moving towards idle
+ *
+ * If the new value of the ->dynticks_nesting counter now is zero,
+ * we really have entered idle, and must do the appropriate accounting.
+ * The caller must have disabled interrupts.
+ */
+static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
+{
+	trace_rcu_dyntick("Start", oldval, 0);
+	if (!is_idle_task(current)) {
+		struct task_struct *idle = idle_task(smp_processor_id());
+
+		trace_rcu_dyntick("Error on entry: not idle task", oldval, 0);
+		ftrace_dump(DUMP_ALL);
+		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+			  current->pid, current->comm,
+			  idle->pid, idle->comm); /* must be idle task! */
+	}
+	rcu_prepare_for_idle(smp_processor_id());
+	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
+	smp_mb__before_atomic_inc();  /* See above. */
+	atomic_inc(&rdtp->dynticks);
+	smp_mb__after_atomic_inc();  /* Force ordering with next sojourn. */
+	WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
+}
 
 /**
- * rcu_enter_nohz - inform RCU that current CPU is entering nohz
+ * rcu_idle_enter - inform RCU that current CPU is entering idle
  *
- * Enter nohz mode, in other words, -leave- the mode in which RCU
+ * Enter idle mode, in other words, -leave- the mode in which RCU
  * read-side critical sections can occur.  (Though RCU read-side
- * critical sections can occur in irq handlers in nohz mode, a possibility
- * handled by rcu_irq_enter() and rcu_irq_exit()).
+ * critical sections can occur in irq handlers in idle, a possibility
+ * handled by irq_enter() and irq_exit().)
+ *
+ * We crowbar the ->dynticks_nesting field to zero to allow for
+ * the possibility of usermode upcalls having messed up our count
+ * of interrupt nesting level during the prior busy period.
  */
-void rcu_enter_nohz(void)
+void rcu_idle_enter(void)
 {
 	unsigned long flags;
+	long long oldval;
 	struct rcu_dynticks *rdtp;
 
 	local_irq_save(flags);
 	rdtp = &__get_cpu_var(rcu_dynticks);
-	if (--rdtp->dynticks_nesting) {
-		local_irq_restore(flags);
-		return;
-	}
-	trace_rcu_dyntick("Start");
-	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
-	smp_mb__before_atomic_inc();  /* See above. */
-	atomic_inc(&rdtp->dynticks);
-	smp_mb__after_atomic_inc();  /* Force ordering with next sojourn. */
-	WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
+	oldval = rdtp->dynticks_nesting;
+	rdtp->dynticks_nesting = 0;
+	rcu_idle_enter_common(rdtp, oldval);
 	local_irq_restore(flags);
 }
 
-/*
- * rcu_exit_nohz - inform RCU that current CPU is leaving nohz
+/**
+ * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
+ *
+ * Exit from an interrupt handler, which might possibly result in entering
+ * idle mode, in other words, leaving the mode in which read-side critical
+ * sections can occur.
  *
- * Exit nohz mode, in other words, -enter- the mode in which RCU
- * read-side critical sections normally occur.
+ * This code assumes that the idle loop never does anything that might
+ * result in unbalanced calls to irq_enter() and irq_exit().  If your
+ * architecture violates this assumption, RCU will give you what you
+ * deserve, good and hard.  But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
+ *
+ * You have been warned.
  */
-void rcu_exit_nohz(void)
+void rcu_irq_exit(void)
 {
 	unsigned long flags;
+	long long oldval;
 	struct rcu_dynticks *rdtp;
 
 	local_irq_save(flags);
 	rdtp = &__get_cpu_var(rcu_dynticks);
-	if (rdtp->dynticks_nesting++) {
-		local_irq_restore(flags);
-		return;
-	}
+	oldval =