Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull v3.7 RCU commits from Paul E. McKenney:

"
0.	A fix for a latent bug that has been in RCU ever since the
        addition of CPU stall warnings.  This bug results in
        false-positive stall warnings, but thus far only on embedded
        systems with severely cut-down userspace configurations.
        This fix is located on an rcu/urgent branch, with the rest
        of the commits based on top of it.  This commit CCs stable.
        Given that the merge window is coming quite soon and given
        the small number of affected users, I do -not- recommend
        pushing it to 3.6, but the separate branch makes it easy to
        find if someone needs it.

1.	Further reductions in latency spikes for huge systems, along
        with additional boot-time adaptation to the actual hardware.
        This is a large change, as it moves RCU grace-period
        initialization and cleanup, along with quiescent-state forcing,
        from softirq to a kthread.  However, it appears to be in
        quite good shape (famous last words).  Posted to LKML at
        https://lkml.org/lkml/2012/9/20/427.
2.	Updates to documentation and rcutorture, the latter category
        including keeping statistics on CPU-hotplug latencies and
        fixing some initialization-time races.  Posted to LKML at
        https://lkml.org/lkml/2012/8/30/193.

3.	Miscellaneous fixes and improvements, posted to LKML at
        https://lkml.org/lkml/2012/8/30/199.

4.	CPU-hotplug fixes and improvements, posted to LKML at
        https://lkml.org/lkml/2012/8/30/292 for first three and at
        https://lkml.org/lkml/2012/8/3/416.

5.	Idle-loop fixes that were omitted on an earlier submission,
        posted to LKML at https://lkml.org/lkml/2012/8/30/251.
"

Signed-off-by: Ingo Molnar <mingo@kernel.org>

17 files changed, 1248 insertions, 1123 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index c0cc67ad764c..e5602d32acb3 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -10,7 +10,7 @@ obj-y     = fork.o exec_domain.o panic.o printk.o \
 	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
 	    hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
 	    notifier.o ksysfs.o cred.o \
-	    async.o range.o groups.o lglock.o
+	    async.o range.o groups.o lglock.o smpboot.o
 
 ifdef CONFIG_FUNCTION_TRACER
 # Do not trace debug files and internal ftrace files
@@ -46,7 +46,6 @@ obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o
 obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o
 obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
 obj-$(CONFIG_SMP) += smp.o
-obj-$(CONFIG_SMP) += smpboot.o
 ifneq ($(CONFIG_SMP),y)
 obj-y += up.o
 endif
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 14d32588cccd..e615dfbcf794 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -280,12 +280,13 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 				__func__, cpu);
 		goto out_release;
 	}
+	smpboot_park_threads(cpu);
 
 	err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
 	if (err) {
 		/* CPU didn't die: tell everyone.  Can't complain. */
+		smpboot_unpark_threads(cpu);
 		cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
-
 		goto out_release;
 	}
 	BUG_ON(cpu_online(cpu));
@@ -354,6 +355,10 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
 		goto out;
 	}
 
+	ret = smpboot_create_threads(cpu);
+	if (ret)
+		goto out;
+
 	ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
 	if (ret) {
 		nr_calls--;
@@ -368,6 +373,9 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
 		goto out_notify;
 	BUG_ON(!cpu_online(cpu));
 
+	/* Wake the per cpu threads */
+	smpboot_unpark_threads(cpu);
+
 	/* Now call notifier in preparation. */
 	cpu_notify(CPU_ONLINE | mod, hcpu);
 
diff --git a/kernel/kthread.c b/kernel/kthread.c
index b579af57ea10..146a6fa96825 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -37,11 +37,20 @@ struct kthread_create_info
 };
 
 struct kthread {
-	int should_stop;
+	unsigned long flags;
+	unsigned int cpu;
 	void *data;
+	struct completion parked;
 	struct completion exited;
 };
 
+enum KTHREAD_BITS {
+	KTHREAD_IS_PER_CPU = 0,
+	KTHREAD_SHOULD_STOP,
+	KTHREAD_SHOULD_PARK,
+	KTHREAD_IS_PARKED,
+};
+
 #define to_kthread(tsk)	\
 	container_of((tsk)->vfork_done, struct kthread, exited)
 
@@ -52,13 +61,29 @@ struct kthread {
  * and this will return true.  You should then return, and your return
  * value will be passed through to kthread_stop().
  */
-int kthread_should_stop(void)
+bool kthread_should_stop(void)
 {
-	return to_kthread(current)->should_stop;
+	return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
 }
 EXPORT_SYMBOL(kthread_should_stop);
 
 /**
+ * kthread_should_park - should this kthread park now?
+ *
+ * When someone calls kthread_park() on your kthread, it will be woken
+ * and this will return true.  You should then do the necessary
+ * cleanup and call kthread_parkme()
+ *
+ * Similar to kthread_should_stop(), but this keeps the thread alive
+ * and in a park position. kthread_unpark() "restarts" the thread and
+ * calls the thread function again.
+ */
+bool kthread_should_park(void)
+{
+	return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
+}
+
+/**
  * kthread_freezable_should_stop - should this freezable kthread return now?
  * @was_frozen: optional out parameter, indicates whether %current was frozen
  *
@@ -96,6 +121,24 @@ void *kthread_data(struct task_struct *task)
 	return to_kthread(task)->data;
 }
 
+static void __kthread_parkme(struct kthread *self)
+{
+	__set_current_state(TASK_INTERRUPTIBLE);
+	while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
+		if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
+			complete(&self->parked);
+		schedule();
+		__set_current_state(TASK_INTERRUPTIBLE);
+	}
+	clear_bit(KTHREAD_IS_PARKED, &self->flags);
+	__set_current_state(TASK_RUNNING);
+}
+
+void kthread_parkme(void)
+{
+	__kthread_parkme(to_kthread(current));
+}
+
 static int kthread(void *_create)
 {
 	/* Copy data: it's on kthread's stack */
@@ -105,9 +148,10 @@ static int kthread(void *_create)
 	struct kthread self;
 	int ret;
 
-	self.should_stop = 0;
+	self.flags = 0;
 	self.data = data;
 	init_completion(&self.exited);
+	init_completion(&self.parked);
 	current->vfork_done = &self.exited;
 
 	/* OK, tell user we're spawned, wait for stop or wakeup */
@@ -117,9 +161,11 @@ static int kthread(void *_create)
 	schedule();
 
 	ret = -EINTR;
-	if (!self.should_stop)
-		ret = threadfn(data);
 
+	if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) {
+		__kthread_parkme(&self);
+		ret = threadfn(data);
+	}
 	/* we can't just return, we must preserve "self" on stack */
 	do_exit(ret);
 }
@@ -172,8 +218,7 @@ static void create_kthread(struct kthread_create_info *create)
  * Returns a task_struct or ERR_PTR(-ENOMEM).
  */
 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
-					   void *data,
-					   int node,
+					   void *data, int node,
 					   const char namefmt[],
 					   ...)
 {
@@ -210,6 +255,13 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
 }
 EXPORT_SYMBOL(kthread_create_on_node);
 
+static void __kthread_bind(struct task_struct *p, unsigned int cpu)
+{
+	/* It's safe because the task is inactive. */
+	do_set_cpus_allowed(p, cpumask_of(cpu));
+	p->flags |= PF_THREAD_BOUND;
+}
+
 /**
  * kthread_bind - bind a just-created kthread to a cpu.
  * @p: thread created by kthread_create().
@@ -226,14 +278,112 @@ void kthread_bind(struct task_struct *p, unsigned int cpu)
 		WARN_ON(1);
 		return;
 	}
-
-	/* It's safe because the task is inactive. */
-	do_set_cpus_allowed(p, cpumask_of(cpu));
-	p->flags |= PF_THREAD_BOUND;
+	__kthread_bind(p, cpu);
 }
 EXPORT_SYMBOL(kthread_bind);
 
 /**
+ * kthread_create_on_cpu - Create a cpu bound kthread
+ * @threadfn: the function to run until signal_pending(current).
+ * @data: data ptr for @threadfn.
+ * @cpu: The cpu on which the thread should be bound,
+ * @namefmt: printf-style name for the thread. Format is restricted
+ *	     to "name.*%u". Code fills in cpu number.
+ *
+ * Description: This helper function creates and names a kernel thread
+ * The thread will be woken and put into park mode.
+ */
+struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
+					  void *data, unsigned int cpu,
+					  const char *namefmt)
+{
+	struct task_struct *p;
+
+	p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
+				   cpu);
+	if (IS_ERR(p))
+		return p;
+	set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
+	to_kthread(p)->cpu = cpu;
+	/* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */
+	kthread_park(p);
+	return p;
+}
+
+static struct kthread *task_get_live_kthread(struct task_struct *k)
+{
+	struct kthread *kthread;
+
+	get_task_struct(k);
+	kthread = to_kthread(k);
+	/* It might have exited */
+	barrier();
+	if (k->vfork_done != NULL)
+		return kthread;
+	return NULL;
+}
+
+/**
+ * kthread_unpark - unpark a thread created by kthread_create().
+ * @k:		thread created by kthread_create().
+ *
+ * Sets kthread_should_park() for @k to return false, wakes it, and
+ * waits for it to return. If the thread is marked percpu then its
+ * bound to the cpu again.
+ */
+void kthread_unpark(struct task_struct *k)
+{
+	struct kthread *kthread = task_get_live_kthread(k);
+
+	if (kthread) {
+		clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
+		/*
+		 * We clear the IS_PARKED bit here as we don't wait
+		 * until the task has left the park code. So if we'd
+		 * park before that happens we'd see the IS_PARKED bit
+		 * which might be about to be cleared.
+		 */
+		if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
+			if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
+				__kthread_bind(k, kthread->cpu);
+			wake_up_process(k);
+		}
+	}
+	put_task_struct(k);
+}
+
+/**
+ * kthread_park - park a thread created by kthread_create().
+ * @k: thread created by kthread_create().
+ *
+ * Sets kthread_should_park() for @k to return true, wakes it, and
+ * waits for it to return. This can also be called after kthread_create()
+ * instead of calling wake_up_process(): the thread will park without
+ * calling threadfn().
+ *
+ * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
+ * If called by the kthread itself just the park bit is set.
+ */
+int kthread_park(struct task_struct *k)
+{
+	struct kthread *kthread = task_get_live_kthread(k);
+	int ret = -ENOSYS;
+
+	if (kthread) {
+		if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
+			set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
+			if (k != current) {
+				wake_up_process(k);
+				wait_for_completion(&kthread->parked);
+			}
+		}
+		ret = 0;
+	}
+	put_task_struct(k);
+	return ret;
+}
+
+/**
  * kthread_stop - stop a thread created by kthread_create().
  * @k: thread created by kthread_create().
  *
@@ -250,16 +400,13 @@ EXPORT_SYMBOL(kthread_bind);
  */
 int kthread_stop(struct task_struct *k)
 {
-	struct kthread *kthread;
+	struct kthread *kthread = task_get_live_kthread(k);
 	int ret;
 
 	trace_sched_kthread_stop(k);
-	get_task_struct(k);
-
-	kthread = to_kthread(k);
-	barrier(); /* it might have exited */
-	if (k->vfork_done != NULL) {
-		kthread->should_stop = 1;
+	if (kthread) {
+		set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
+		clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
 		wake_up_process(k);
 		wait_for_completion(&kthread->exited);
 	}
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 4e6a61b15e86..29ca1c6da594 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -45,6 +45,7 @@
 #include <linux/mutex.h>
 #include <linux/export.h>
 #include <linux/hardirq.h>
+#include <linux/delay.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/rcu.h>
@@ -81,6 +82,9 @@ void __rcu_read_unlock(void)
 	} else {
 		barrier();  /* critical section before exit code. */
 		t->rcu_read_lock_nesting = INT_MIN;
+#ifdef CONFIG_PROVE_RCU_DELAY
+		udelay(10); /* Make preemption more probable. */
+#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
 		barrier();  /* assign before ->rcu_read_unlock_special load */
 		if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
 			rcu_read_unlock_special(t);
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 547b1fe5b052..e4c6a598d6f7 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -56,25 +56,28 @@ static void __call_rcu(struct rcu_head *head,
 static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
 
 /* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
-static void rcu_idle_enter_common(long long oldval)
+static void rcu_idle_enter_common(long long newval)
 {
-	if (rcu_dynticks_nesting) {
+	if (newval) {
 		RCU_TRACE(trace_rcu_dyntick("--=",
-					    oldval, rcu_dynticks_nesting));
+					    rcu_dynticks_nesting, newval));
+		rcu_dynticks_nesting = newval;
 		return;
 	}
-	RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
+	RCU_TRACE(trace_rcu_dyntick("Start", rcu_dynticks_nesting, newval));
 	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));
+					    rcu_dynticks_nesting, newval));
 		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) */
+	barrier();
+	rcu_dynticks_nesting = newval;
 }
 
 /*
@@ -84,17 +87,16 @@ static void rcu_idle_enter_common(long long oldval)
 void rcu_idle_enter(void)
 {
 	unsigned long flags;
-	long long oldval;
+	long long newval;
 
 	local_irq_save(flags);
-	oldval = rcu_dynticks_nesting;
 	WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0);
 	if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) ==
 	    DYNTICK_TASK_NEST_VALUE)
-		rcu_dynticks_nesting = 0;
+		newval = 0;
 	else
-		rcu_dynticks_nesting  -= DYNTICK_TASK_NEST_VALUE;
-	rcu_idle_enter_common(oldval);
+		newval = rcu_dynticks_nesting - DYNTICK_TASK_NEST_VALUE;
+	rcu_idle_enter_common(newval);
 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_enter);
@@ -105,15 +107,15 @@ EXPORT_SYMBOL_GPL(rcu_idle_enter);
 void rcu_irq_exit(void)
 {
 	unsigned long flags;
-	long long oldval;
+	long long newval;
 
 	local_irq_save(flags);
-	oldval = rcu_dynticks_nesting;
-	rcu_dynticks_nesting--;
-	WARN_ON_ONCE(rcu_dynticks_nesting < 0);
-	rcu_idle_enter_common(oldval);
+	newval = rcu_dynticks_nesting - 1;
+	WARN_ON_ONCE(newval < 0);
+	rcu_idle_enter_common(newval);
 	local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_irq_exit);
 
 /* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
 static void rcu_idle_exit_common(long long oldval)
@@ -171,6 +173,7 @@ void rcu_irq_enter(void)
 	rcu_idle_exit_common(oldval);
 	local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_irq_enter);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 918fd1e8509c..3d0190282204 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -278,7 +278,7 @@ static int rcu_boost(void)
 	    rcu_preempt_ctrlblk.exp_tasks == NULL)
 		return 0;  /* Nothing to boost. */
 
-	raw_local_irq_save(flags);
+	local_irq_save(flags);
 
 	/*
 	 * Recheck with irqs disabled: all tasks in need of boosting
@@ -287,7 +287,7 @@ static int rcu_boost(void)
 	 */
 	if (rcu_preempt_ctrlblk.boost_tasks == NULL &&
 	    rcu_preempt_ctrlblk.exp_tasks == NULL) {
-		raw_local_irq_restore(flags);
+		local_irq_restore(flags);
 		return 0;
 	}
 
@@ -317,7 +317,7 @@ static int rcu_boost(void)
 	t = container_of(tb, struct task_struct, rcu_node_entry);
 	rt_mutex_init_proxy_locked(&mtx, t);
 	t->rcu_boost_mutex = &mtx;
-	raw_local_irq_restore(flags);
+	local_irq_restore(flags);
 	rt_mutex_lock(&mtx);
 	rt_mutex_unlock(&mtx);  /* Keep lockdep happy. */
 
@@ -991,9 +991,9 @@ static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
 {
 	unsigned long flags;
 
-	raw_local_irq_save(flags);
+	local_irq_save(flags);
 	rcp->qlen -= n;
-	raw_local_irq_restore(flags);
+	local_irq_restore(flags);
 }
 
 /*
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 25b15033c61f..aaa7b9f3532a 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -53,10 +53,11 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@fre
 
 static int nreaders = -1;	/* # reader threads, defaults to 2*ncpus */
 static int nfakewriters = 4;	/* # fake writer threads */
-static int stat_interval;	/* Interval between stats, in seconds. */
-				/*  Defaults to "only at end of test". */
+static int stat_interval = 60;	/* Interval between stats, in seconds. */
+				/*  Zero means "only at end of test". */
 static bool verbose;		/* Print more debug info. */
-static bool test_no_idle_hz;	/* Test RCU's support for tickless idle CPUs. */
+static bool test_no_idle_hz = true;
+				/* Test RCU 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). */
@@ -119,11 +120,11 @@ MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
 
 #define TORTURE_FLAG "-torture:"
 #define PRINTK_STRING(s) \
-	do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
+	do { pr_alert("%s" TORTURE_FLAG s "\n", torture_type); } while (0)
 #define VERBOSE_PRINTK_STRING(s) \
-	do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
+	do { if (verbose) pr_alert("%s" TORTURE_FLAG s "\n", torture_type); } while (0)
 #define VERBOSE_PRINTK_ERRSTRING(s) \
-	do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
+	do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
 
 static char printk_buf[4096];
 
@@ -176,8 +177,14 @@ static long n_rcu_torture_boosts;
 static long n_rcu_torture_timers;
 static long n_offline_attempts;
 static long n_offline_successes;
+static unsigned long sum_offline;
+static int min_offline = -1;
+static int max_offline;
 static long n_online_attempts;
 static long n_online_successes;
+static unsigned long sum_online;
+static int min_online = -1;
+static int max_online;
 static long n_barrier_attempts;
 static long n_barrier_successes;
 static struct list_head rcu_torture_removed;
@@ -235,7 +242,7 @@ rcutorture_shutdown_notify(struct notifier_block *unused1,
 	if (fullstop == FULLSTOP_DONTSTOP)
 		fullstop = FULLSTOP_SHUTDOWN;
 	else
-		printk(KERN_WARNING /* but going down anyway, so... */
+		pr_warn(/* but going down anyway, so... */
 		       "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
 	mutex_unlock(&fullstop_mutex);
 	return NOTIFY_DONE;
@@ -248,7 +255,7 @@ rcutorture_shutdown_notify(struct notifier_block *unused1,
 static void rcutorture_shutdown_absorb(char *title)
 {
 	if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
-		printk(KERN_NOTICE
+		pr_notice(
 		       "rcutorture thread %s parking due to system shutdown\n",
 		       title);
 		schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
@@ -1214,11 +1221,13 @@ rcu_torture_printk(char *page)
 		       n_rcu_torture_boost_failure,
 		       n_rcu_torture_boosts,
 		       n_rcu_torture_timers);
-	cnt += sprintf(&page[cnt], "onoff: %ld/%ld:%ld/%ld ",
-		       n_online_successes,
-		       n_online_attempts,
-		       n_offline_successes,
-		       n_offline_attempts);
+	cnt += sprintf(&page[cnt],
+		       "onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
+		       n_online_successes, n_online_attempts,
+		       n_offline_successes, n_offline_attempts,
+		       min_online, max_online,
+		       min_offline, max_offline,
+		       sum_online, sum_offline, HZ);
 	cnt += sprintf(&page[cnt], "barrier: %ld/%ld:%ld",
 		       n_barrier_successes,
 		       n_barrier_attempts,
@@ -1267,7 +1276,7 @@ rcu_torture_stats_print(void)
 	int cnt;
 
 	cnt = rcu_torture_printk(printk_buf);
-	printk(KERN_ALERT "%s", printk_buf);
+	pr_alert("%s", printk_buf);
 }
 
 /*
@@ -1380,20 +1389,20 @@ rcu_torture_stutter(void *arg)
 static inline void
 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
 {
-	printk(KERN_ALERT "%s" TORTURE_FLAG
-		"--- %s: nreaders=%d nfakewriters=%d "
-		"stat_interval=%d verbose=%d test_no_idle_hz=%d "
-		"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 shutdown_secs=%d "
-		"onoff_interval=%d onoff_holdoff=%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, shutdown_secs,
-		onoff_interval, onoff_holdoff);
+	pr_alert("%s" TORTURE_FLAG
+		 "--- %s: nreaders=%d nfakewriters=%d "
+		 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
+		 "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 shutdown_secs=%d "
+		 "onoff_interval=%d onoff_holdoff=%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, shutdown_secs,
+		 onoff_interval, onoff_holdoff);
 }
 
 static struct notifier_block rcutorture_shutdown_nb = {
@@ -1460,9 +1469,9 @@ rcu_torture_shutdown(void *arg)
 	       !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);
+			pr_alert("%s" TORTURE_FLAG
+				 "rcu_torture_shutdown task: %lu jiffies remaining\n",
+				 torture_type, delta);
 		schedule_timeout_interruptible(delta);
 		jiffies_snap = ACCESS_ONCE(jiffies);
 	}
@@ -1490,8 +1499,10 @@ static int __cpuinit
 rcu_torture_onoff(void *arg)
 {
 	int cpu;
+	unsigned long delta;
 	int maxcpu = -1;
 	DEFINE_RCU_RANDOM(rand);
+	unsigned long starttime;
 
 	VERBOSE_PRINTK_STRING("rcu_torture_onoff task started");
 	for_each_online_cpu(cpu)
@@ -1506,29 +1517,51 @@ rcu_torture_onoff(void *arg)
 		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);
+				pr_alert("%s" TORTURE_FLAG
+					 "rcu_torture_onoff task: offlining %d\n",
+					 torture_type, cpu);
+			starttime = jiffies;
 			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);
+					pr_alert("%s" TORTURE_FLAG
+						 "rcu_torture_onoff task: offlined %d\n",
+						 torture_type, cpu);
 				n_offline_successes++;
+				delta = jiffies - starttime;
+				sum_offline += delta;
+				if (min_offline < 0) {
+					min_offline = delta;
+					max_offline = delta;
+				}
+				if (min_offline > delta)
+					min_offline = delta;
+				if (max_offline < delta)
+					max_offline = delta;
 			}
 		} else if (cpu_is_hotpluggable(cpu)) {
 			if (verbose)
-				printk(KERN_ALERT "%s" TORTURE_FLAG
-				       "rcu_torture_onoff task: onlining %d\n",
-				       torture_type, cpu);
+				pr_alert("%s" TORTURE_FLAG
+					 "rcu_torture_onoff task: onlining %d\n",
+					 torture_type, cpu);
+			starttime = jiffies;
 			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);
+					pr_alert("%s" TORTURE_FLAG
+						 "rcu_torture_onoff task: onlined %d\n",
+						 torture_type, cpu);
 				n_online_successes++;
+				delta = jiffies - starttime;
+				sum_online += delta;
+				if (min_online < 0) {
+					min_online = delta;
+					max_online = delta;
+				}
+				if (min_online > delta)
+					min_online = delta;
+				if (max_online < delta)
+					max_online = delta;
 			}
 		}
 		schedule_timeout_interruptible(onoff_interval * HZ);
@@ -1593,14 +1626,14 @@ static int __cpuinit rcu_torture_stall(void *args)
 	if (!kthread_should_stop()) {
 		stop_at = get_seconds() + stall_cpu;
 		/* RCU CPU stall is expected behavior in following code. */
-		printk(KERN_ALERT "rcu_torture_stall start.\n");
+		pr_alert("rcu_torture_stall start.\n");
 		rcu_read_lock();
 		preempt_disable();
 		while (ULONG_CMP_LT(get_seconds(), stop_at))
 			continue;  /* Induce RCU CPU stall warning. */
 		preempt_enable();
 		rcu_read_unlock();
-		printk(KERN_ALERT "rcu_torture_stall end.\n");
+		pr_alert("rcu_torture_stall end.\n");
 	}
 	rcutorture_shutdown_absorb("rcu_torture_stall");
 	while (!kthread_should_stop())
@@ -1716,12 +1749,12 @@ static int rcu_torture_barrier_init(void)
 	if (n_barrier_cbs == 0)
 		return 0;
 	if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
-		printk(KERN_ALERT "%s" TORTURE_FLAG
-		       " Call or barrier ops missing for %s,\n",
-		       torture_type, cur_ops->name);
-		printk(KERN_ALERT "%s" TORTURE_FLAG
-		       " RCU barrier testing omitted from run.\n",
-		       torture_type);
+		pr_alert("%s" TORTURE_FLAG
+			 " Call or barrier ops missing for %s,\n",
+			 torture_type, cur_ops->name);
+		pr_alert("%s" TORTURE_FLAG
+			 " RCU barrier testing omitted from run.\n",
+			 torture_type);
 		return 0;
 	}
 	atomic_set(&barrier_cbs_count, 0);
@@ -1814,7 +1847,7 @@ rcu_torture_cleanup(void)
 	mutex_lock(&fullstop_mutex);
 	rcutorture_record_test_transition();
 	if (fullstop == FULLSTOP_SHUTDOWN) {
-		printk(KERN_WARNING /* but going down anyway, so... */
+		pr_warn(/* but going down anyway, so... */
 		       "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
 		mutex_unlock(&fullstop_mutex);
 		schedule_timeout_uninterruptible(10);
@@ -1938,17 +1971,17 @@ rcu_torture_init(void)
 			break;
 	}
 	if (i == ARRAY_SIZE(torture_ops)) {
-		printk(KERN_ALERT "rcu-torture: invalid torture type: \"%s\"\n",
-		       torture_type);
-		printk(KERN_ALERT "rcu-torture types:");
+		pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
+			 torture_type);
+		pr_alert("rcu-torture types:");
 		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
-			printk(KERN_ALERT " %s", torture_ops[i]->name);
-		printk(KERN_ALERT "\n");
+			pr_alert(" %s", torture_ops[i]->name);
+		pr_alert("\n");
 		mutex_unlock(&fullstop_mutex);
 		return -EINVAL;
 	}
 	if (cur_ops->fqs == NULL && fqs_duration != 0) {
-		printk(KERN_ALERT "rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
+		pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
 		fqs_duration = 0;
 	}
 	if (cur_ops->init)
@@ -1996,14 +2029,15 @@ rcu_torture_init(void)
 	/* Start up the kthreads. */
 
 	VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
-	writer_task = kthread_run(rcu_torture_writer, NULL,
-				  "rcu_torture_writer");
+	writer_task = kthread_create(rcu_torture_writer, NULL,
+				     "rcu_torture_writer");
 	if (IS_ERR(writer_task)) {
 		firsterr = PTR_ERR(writer_task);
 		VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
 		writer_task = NULL;
 		goto unwind;
 	}
+	wake_up_process(writer_task);
 	fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
 				   GFP_KERNEL);
 	if (fakewriter_tasks == NULL) {
@@ -2118,14 +2152,15 @@ 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");
+		shutdown_task = kthread_create(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;
 		}
+		wake_up_process(shutdown_task);
 	}
 	i = rcu_torture_onoff_init();
 	if (i != 0) {
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f280e542e3e9..7387e46009d9 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -52,6 +52,7 @@
 #include <linux/prefetch.h>
 #include <linux/delay.h>
 #include <linux/stop_machine.h>
+#include <linux/random.h>
 
 #include "rcutree.h"
 #include <trace/events/rcu.h>
@@ -61,6 +62,7 @@
 /* Data structures. */
 
 static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
+static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
 
 #define RCU_STATE_INITIALIZER(sname, cr) { \
 	.level = { &sname##_state.node[0] }, \
@@ -72,7 +74,6 @@ static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
 	.orphan_nxttail = &sname##_state.orphan_nxtlist, \
 	.orphan_donetail = &sname##_state.orphan_donelist, \
 	.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
-	.fqslock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.fqslock), \
 	.name = #sname, \
 }
 
@@ -88,7 +89,7 @@ LIST_HEAD(rcu_struct_flavors);
 
 /* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
 static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF;
-module_param(rcu_fanout_leaf, int, 0);
+module_param(rcu_fanout_leaf, int, 0444);
 int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
 static int num_rcu_lvl[] = {  /* Number of rcu_nodes at specified level. */
 	NUM_RCU_LVL_0,
@@ -133,13 +134,12 @@ static int rcu_scheduler_fully_active __read_mostly;
  */
 static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
-DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
 DEFINE_PER_CPU(char, rcu_cpu_has_work);
 
 #endif /* #ifdef CONFIG_RCU_BOOST */