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

Pull RCU updates from Ingo Molnar:
 "The major changes:

  - Simplify RCU's grace-period and callback processing based on the new
    numbering for callbacks.

  - Removal of TINY_PREEMPT_RCU in favor of TREE_PREEMPT_RCU for
    single-CPU low-latency systems.

  - SRCU-related changes and fixes.

  - Miscellaneous fixes, including converting a few remaining printk()
    calls to pr_*().

  - Documentation updates"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
  rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs
  rcu: Shrink TINY_RCU by moving exit_rcu()
  rcu: Remove TINY_PREEMPT_RCU tracing documentation
  rcu: Consolidate rcutiny_plugin.h ifdefs
  rcu: Remove rcu_preempt_note_context_switch()
  rcu: Remove the CONFIG_TINY_RCU ifdefs in rcutiny.h
  rcu: Remove check_cpu_stall_preempt()
  rcu: Simplify RCU_TINY RCU callback invocation
  rcu: Remove rcu_preempt_process_callbacks()
  rcu: Remove rcu_preempt_remove_callbacks()
  rcu: Remove rcu_preempt_check_callbacks()
  rcu: Remove show_tiny_preempt_stats()
  rcu: Remove TINY_PREEMPT_RCU
  powerpc,kvm: fix imbalance srcu_read_[un]lock()
  rcu: Remove srcu_read_lock_raw() and srcu_read_unlock_raw().
  rcu: Apply Dave Jones's NOCB Kconfig help feedback
  rcu: Merge adjacent identical ifdefs
  rcu: Drive quiescent-state-forcing delay from HZ
  rcu: Remove "Experimental" flags
  kthread: Add kworker kthreads to OS-jitter documentation
  ...

7 files changed, 154 insertions, 1208 deletions

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 48ab70384a4c..cce6ba8bbace 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -104,31 +104,7 @@ void __rcu_read_unlock(void)
 }
 EXPORT_SYMBOL_GPL(__rcu_read_unlock);
 
-/*
- * Check for a task exiting while in a preemptible-RCU read-side
- * critical section, clean up if so.  No need to issue warnings,
- * as debug_check_no_locks_held() already does this if lockdep
- * is enabled.
- */
-void exit_rcu(void)
-{
-	struct task_struct *t = current;
-
-	if (likely(list_empty(&current->rcu_node_entry)))
-		return;
-	t->rcu_read_lock_nesting = 1;
-	barrier();
-	t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
-	__rcu_read_unlock();
-}
-
-#else /* #ifdef CONFIG_PREEMPT_RCU */
-
-void exit_rcu(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 static struct lock_class_key rcu_lock_key;
@@ -145,9 +121,6 @@ static struct lock_class_key rcu_sched_lock_key;
 struct lockdep_map rcu_sched_lock_map =
 	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
 EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
-#endif
-
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
 
 int debug_lockdep_rcu_enabled(void)
 {
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index a0714a51b6d7..aa344111de3e 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -44,7 +44,6 @@
 
 /* Forward declarations for rcutiny_plugin.h. */
 struct rcu_ctrlblk;
-static void invoke_rcu_callbacks(void);
 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
 static void rcu_process_callbacks(struct softirq_action *unused);
 static void __call_rcu(struct rcu_head *head,
@@ -205,7 +204,7 @@ static int rcu_is_cpu_rrupt_from_idle(void)
  */
 static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
 {
-	reset_cpu_stall_ticks(rcp);
+	RCU_TRACE(reset_cpu_stall_ticks(rcp));
 	if (rcp->rcucblist != NULL &&
 	    rcp->donetail != rcp->curtail) {
 		rcp->donetail = rcp->curtail;
@@ -227,7 +226,7 @@ void rcu_sched_qs(int cpu)
 	local_irq_save(flags);
 	if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
 	    rcu_qsctr_help(&rcu_bh_ctrlblk))
-		invoke_rcu_callbacks();
+		raise_softirq(RCU_SOFTIRQ);
 	local_irq_restore(flags);
 }
 
@@ -240,7 +239,7 @@ void rcu_bh_qs(int cpu)
 
 	local_irq_save(flags);
 	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
-		invoke_rcu_callbacks();
+		raise_softirq(RCU_SOFTIRQ);
 	local_irq_restore(flags);
 }
 
@@ -252,12 +251,11 @@ void rcu_bh_qs(int cpu)
  */
 void rcu_check_callbacks(int cpu, int user)
 {
-	check_cpu_stalls();
+	RCU_TRACE(check_cpu_stalls());
 	if (user || rcu_is_cpu_rrupt_from_idle())
 		rcu_sched_qs(cpu);
 	else if (!in_softirq())
 		rcu_bh_qs(cpu);
-	rcu_preempt_check_callbacks();
 }
 
 /*
@@ -278,7 +276,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 					      ACCESS_ONCE(rcp->rcucblist),
 					      need_resched(),
 					      is_idle_task(current),
-					      rcu_is_callbacks_kthread()));
+					      false));
 		return;
 	}
 
@@ -290,7 +288,6 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 	*rcp->donetail = NULL;
 	if (rcp->curtail == rcp->donetail)
 		rcp->curtail = &rcp->rcucblist;
-	rcu_preempt_remove_callbacks(rcp);
 	rcp->donetail = &rcp->rcucblist;
 	local_irq_restore(flags);
 
@@ -309,14 +306,13 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 	RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
 	RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count, 0, need_resched(),
 				      is_idle_task(current),
-				      rcu_is_callbacks_kthread()));
+				      false));
 }
 
 static void rcu_process_callbacks(struct softirq_action *unused)
 {
 	__rcu_process_callbacks(&rcu_sched_ctrlblk);
 	__rcu_process_callbacks(&rcu_bh_ctrlblk);
-	rcu_preempt_process_callbacks();
 }
 
 /*
@@ -382,3 +378,8 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 	__call_rcu(head, func, &rcu_bh_ctrlblk);
 }
 EXPORT_SYMBOL_GPL(call_rcu_bh);
+
+void rcu_init(void)
+{
+	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+}
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 8a233002faeb..0cd385acccfa 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -53,958 +53,10 @@ static struct rcu_ctrlblk rcu_bh_ctrlblk = {
 };
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
+#include <linux/kernel_stat.h>
+
 int rcu_scheduler_active __read_mostly;
 EXPORT_SYMBOL_GPL(rcu_scheduler_active);
-#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
-
-#ifdef CONFIG_RCU_TRACE
-
-static void check_cpu_stall(struct rcu_ctrlblk *rcp)
-{
-	unsigned long j;
-	unsigned long js;
-
-	if (rcu_cpu_stall_suppress)
-		return;
-	rcp->ticks_this_gp++;
-	j = jiffies;
-	js = rcp->jiffies_stall;
-	if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
-		pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
-		       rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
-		       jiffies - rcp->gp_start, rcp->qlen);
-		dump_stack();
-	}
-	if (*rcp->curtail && ULONG_CMP_GE(j, js))
-		rcp->jiffies_stall = jiffies +
-			3 * rcu_jiffies_till_stall_check() + 3;
-	else if (ULONG_CMP_GE(j, js))
-		rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
-}
-
-static void check_cpu_stall_preempt(void);
-
-#endif /* #ifdef CONFIG_RCU_TRACE */
-
-static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
-{
-#ifdef CONFIG_RCU_TRACE
-	rcp->ticks_this_gp = 0;
-	rcp->gp_start = jiffies;
-	rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
-#endif /* #ifdef CONFIG_RCU_TRACE */
-}
-
-static void check_cpu_stalls(void)
-{
-	RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
-	RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
-	RCU_TRACE(check_cpu_stall_preempt());
-}
-
-#ifdef CONFIG_TINY_PREEMPT_RCU
-
-#include <linux/delay.h>
-
-/* Global control variables for preemptible RCU. */
-struct rcu_preempt_ctrlblk {
-	struct rcu_ctrlblk rcb;	/* curtail: ->next ptr of last CB for GP. */
-	struct rcu_head **nexttail;
-				/* Tasks blocked in a preemptible RCU */
-				/*  read-side critical section while an */
-				/*  preemptible-RCU grace period is in */
-				/*  progress must wait for a later grace */
-				/*  period.  This pointer points to the */
-				/*  ->next pointer of the last task that */
-				/*  must wait for a later grace period, or */
-				/*  to &->rcb.rcucblist if there is no */
-				/*  such task. */
-	struct list_head blkd_tasks;
-				/* Tasks blocked in RCU read-side critical */
-				/*  section.  Tasks are placed at the head */
-				/*  of this list and age towards the tail. */
-	struct list_head *gp_tasks;
-				/* Pointer to the first task blocking the */
-				/*  current grace period, or NULL if there */
-				/*  is no such task. */
-	struct list_head *exp_tasks;
-				/* Pointer to first task blocking the */
-				/*  current expedited grace period, or NULL */
-				/*  if there is no such task.  If there */
-				/*  is no current expedited grace period, */
-				/*  then there cannot be any such task. */
-#ifdef CONFIG_RCU_BOOST
-	struct list_head *boost_tasks;
-				/* Pointer to first task that needs to be */
-				/*  priority-boosted, or NULL if no priority */
-				/*  boosting is needed.  If there is no */
-				/*  current or expedited grace period, there */
-				/*  can be no such task. */
-#endif /* #ifdef CONFIG_RCU_BOOST */
-	u8 gpnum;		/* Current grace period. */
-	u8 gpcpu;		/* Last grace period blocked by the CPU. */
-	u8 completed;		/* Last grace period completed. */
-				/*  If all three are equal, RCU is idle. */
-#ifdef CONFIG_RCU_BOOST
-	unsigned long boost_time; /* When to start boosting (jiffies) */
-#endif /* #ifdef CONFIG_RCU_BOOST */
-#ifdef CONFIG_RCU_TRACE
-	unsigned long n_grace_periods;
-#ifdef CONFIG_RCU_BOOST
-	unsigned long n_tasks_boosted;
-				/* Total number of tasks boosted. */
-	unsigned long n_exp_boosts;
-				/* Number of tasks boosted for expedited GP. */
-	unsigned long n_normal_boosts;
-				/* Number of tasks boosted for normal GP. */
-	unsigned long n_balk_blkd_tasks;
-				/* Refused to boost: no blocked tasks. */
-	unsigned long n_balk_exp_gp_tasks;
-				/* Refused to boost: nothing blocking GP. */
-	unsigned long n_balk_boost_tasks;
-				/* Refused to boost: already boosting. */
-	unsigned long n_balk_notyet;
-				/* Refused to boost: not yet time. */
-	unsigned long n_balk_nos;
-				/* Refused to boost: not sure why, though. */
-				/*  This can happen due to race conditions. */
-#endif /* #ifdef CONFIG_RCU_BOOST */
-#endif /* #ifdef CONFIG_RCU_TRACE */
-};
-
-static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = {
-	.rcb.donetail = &rcu_preempt_ctrlblk.rcb.rcucblist,
-	.rcb.curtail = &rcu_preempt_ctrlblk.rcb.rcucblist,
-	.nexttail = &rcu_preempt_ctrlblk.rcb.rcucblist,
-	.blkd_tasks = LIST_HEAD_INIT(rcu_preempt_ctrlblk.blkd_tasks),
-	RCU_TRACE(.rcb.name = "rcu_preempt")
-};
-
-static int rcu_preempted_readers_exp(void);
-static void rcu_report_exp_done(void);
-
-/*
- * Return true if the CPU has not yet responded to the current grace period.
- */
-static int rcu_cpu_blocking_cur_gp(void)
-{
-	return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum;
-}
-
-/*
- * Check for a running RCU reader.  Because there is only one CPU,
- * there can be but one running RCU reader at a time.  ;-)
- *
- * Returns zero if there are no running readers.  Returns a positive
- * number if there is at least one reader within its RCU read-side
- * critical section.  Returns a negative number if an outermost reader
- * is in the midst of exiting from its RCU read-side critical section
- *
- * Returns zero if there are no running readers.  Returns a positive
- * number if there is at least one reader within its RCU read-side
- * critical section.  Returns a negative number if an outermost reader
- * is in the midst of exiting from its RCU read-side critical section.
- */
-static int rcu_preempt_running_reader(void)
-{
-	return current->rcu_read_lock_nesting;
-}
-
-/*
- * Check for preempted RCU readers blocking any grace period.
- * If the caller needs a reliable answer, it must disable hard irqs.
- */
-static int rcu_preempt_blocked_readers_any(void)
-{
-	return !list_empty(&rcu_preempt_ctrlblk.blkd_tasks);
-}
-
-/*
- * Check for preempted RCU readers blocking the current grace period.
- * If the caller needs a reliable answer, it must disable hard irqs.
- */
-static int rcu_preempt_blocked_readers_cgp(void)
-{
-	return rcu_preempt_ctrlblk.gp_tasks != NULL;
-}
-
-/*
- * Return true if another preemptible-RCU grace period is needed.
- */
-static int rcu_preempt_needs_another_gp(void)
-{
-	return *rcu_preempt_ctrlblk.rcb.curtail != NULL;
-}
-
-/*
- * Return true if a preemptible-RCU grace period is in progress.
- * The caller must disable hardirqs.
- */
-static int rcu_preempt_gp_in_progress(void)
-{
-	return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum;
-}
-
-/*
- * Advance a ->blkd_tasks-list pointer to the next entry, instead
- * returning NULL if at the end of the list.
- */
-static struct list_head *rcu_next_node_entry(struct task_struct *t)
-{
-	struct list_head *np;
-
-	np = t->rcu_node_entry.next;
-	if (np == &rcu_preempt_ctrlblk.blkd_tasks)
-		np = NULL;
-	return np;
-}
-
-#ifdef CONFIG_RCU_TRACE
-
-#ifdef CONFIG_RCU_BOOST
-static void rcu_initiate_boost_trace(void);
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
-/*
- * Dump additional statistice for TINY_PREEMPT_RCU.
- */
-static void show_tiny_preempt_stats(struct seq_file *m)
-{
-	seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n",
-		   rcu_preempt_ctrlblk.rcb.qlen,
-		   rcu_preempt_ctrlblk.n_grace_periods,
-		   rcu_preempt_ctrlblk.gpnum,
-		   rcu_preempt_ctrlblk.gpcpu,
-		   rcu_preempt_ctrlblk.completed,
-		   "T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)],
-		   "N."[!rcu_preempt_ctrlblk.gp_tasks],
-		   "E."[!rcu_preempt_ctrlblk.exp_tasks]);
-#ifdef CONFIG_RCU_BOOST
-	seq_printf(m, "%sttb=%c ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n",
-		   "             ",
-		   "B."[!rcu_preempt_ctrlblk.boost_tasks],
-		   rcu_preempt_ctrlblk.n_tasks_boosted,
-		   rcu_preempt_ctrlblk.n_exp_boosts,
-		   rcu_preempt_ctrlblk.n_normal_boosts,
-		   (int)(jiffies & 0xffff),
-		   (int)(rcu_preempt_ctrlblk.boost_time & 0xffff));
-	seq_printf(m, "%s: nt=%lu egt=%lu bt=%lu ny=%lu nos=%lu\n",
-		   "             balk",
-		   rcu_preempt_ctrlblk.n_balk_blkd_tasks,
-		   rcu_preempt_ctrlblk.n_balk_exp_gp_tasks,
-		   rcu_preempt_ctrlblk.n_balk_boost_tasks,
-		   rcu_preempt_ctrlblk.n_balk_notyet,
-		   rcu_preempt_ctrlblk.n_balk_nos);
-#endif /* #ifdef CONFIG_RCU_BOOST */
-}
-
-#endif /* #ifdef CONFIG_RCU_TRACE */
-
-#ifdef CONFIG_RCU_BOOST
-
-#include "rtmutex_common.h"
-
-#define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO
-
-/* Controls for rcu_kthread() kthread. */
-static struct task_struct *rcu_kthread_task;
-static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
-static unsigned long have_rcu_kthread_work;
-
-/*
- * Carry out RCU priority boosting on the task indicated by ->boost_tasks,
- * and advance ->boost_tasks to the next task in the ->blkd_tasks list.
- */
-static int rcu_boost(void)
-{
-	unsigned long flags;
-	struct rt_mutex mtx;
-	struct task_struct *t;
-	struct list_head *tb;
-
-	if (rcu_preempt_ctrlblk.boost_tasks == NULL &&
-	    rcu_preempt_ctrlblk.exp_tasks == NULL)
-		return 0;  /* Nothing to boost. */
-
-	local_irq_save(flags);
-
-	/*
-	 * Recheck with irqs disabled: all tasks in need of boosting
-	 * might exit their RCU read-side critical sections on their own
-	 * if we are preempted just before disabling irqs.
-	 */
-	if (rcu_preempt_ctrlblk.boost_tasks == NULL &&
-	    rcu_preempt_ctrlblk.exp_tasks == NULL) {
-		local_irq_restore(flags);
-		return 0;
-	}
-
-	/*
-	 * Preferentially boost tasks blocking expedited grace periods.
-	 * This cannot starve the normal grace periods because a second
-	 * expedited grace period must boost all blocked tasks, including
-	 * those blocking the pre-existing normal grace period.
-	 */
-	if (rcu_preempt_ctrlblk.exp_tasks != NULL) {
-		tb = rcu_preempt_ctrlblk.exp_tasks;
-		RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++);
-	} else {
-		tb = rcu_preempt_ctrlblk.boost_tasks;
-		RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++);
-	}
-	RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++);
-
-	/*
-	 * We boost task t by manufacturing an rt_mutex that appears to
-	 * be held by task t.  We leave a pointer to that rt_mutex where
-	 * task t can find it, and task t will release the mutex when it
-	 * exits its outermost RCU read-side critical section.  Then
-	 * simply acquiring this artificial rt_mutex will boost task
-	 * t's priority.  (Thanks to tglx for suggesting this approach!)
-	 */
-	t = container_of(tb, struct task_struct, rcu_node_entry);
-	rt_mutex_init_proxy_locked(&mtx, t);
-	t->rcu_boost_mutex = &mtx;
-	local_irq_restore(flags);
-	rt_mutex_lock(&mtx);
-	rt_mutex_unlock(&mtx);  /* Keep lockdep happy. */
-
-	return ACCESS_ONCE(rcu_preempt_ctrlblk.boost_tasks) != NULL ||
-	       ACCESS_ONCE(rcu_preempt_ctrlblk.exp_tasks) != NULL;
-}
-
-/*
- * Check to see if it is now time to start boosting RCU readers blocking
- * the current grace period, and, if so, tell the rcu_kthread_task to
- * start boosting them.  If there is an expedited boost in progress,
- * we wait for it to complete.
- *
- * If there are no blocked readers blocking the current grace period,
- * return 0 to let the caller know, otherwise return 1.  Note that this
- * return value is independent of whether or not boosting was done.
- */
-static int rcu_initiate_boost(void)
-{
-	if (!rcu_preempt_blocked_readers_cgp() &&
-	    rcu_preempt_ctrlblk.exp_tasks == NULL) {
-		RCU_TRACE(rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++);
-		return 0;
-	}
-	if (rcu_preempt_ctrlblk.exp_tasks != NULL ||
-	    (rcu_preempt_ctrlblk.gp_tasks != NULL &&
-	     rcu_preempt_ctrlblk.boost_tasks == NULL &&
-	     ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time))) {
-		if (rcu_preempt_ctrlblk.exp_tasks == NULL)
-			rcu_preempt_ctrlblk.boost_tasks =
-				rcu_preempt_ctrlblk.gp_tasks;
-		invoke_rcu_callbacks();
-	} else {
-		RCU_TRACE(rcu_initiate_boost_trace());
-	}
-	return 1;
-}
-
-#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)
-
-/*
- * Do priority-boost accounting for the start of a new grace period.
- */
-static void rcu_preempt_boost_start_gp(void)
-{
-	rcu_preempt_ctrlblk.boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES;
-}
-
-#else /* #ifdef CONFIG_RCU_BOOST */
-
-/*
- * If there is no RCU priority boosting, we don't initiate boosting,
- * but we do indicate whether there are blocked readers blocking the
- * current grace period.
- */
-static int rcu_initiate_boost(void)
-{
-	return rcu_preempt_blocked_readers_cgp();
-}
-
-/*
- * If there is no RCU priority boosting, nothing to do at grace-period start.
- */
-static void rcu_preempt_boost_start_gp(void)
-{
-}
-
-#endif /* else #ifdef CONFIG_RCU_BOOST */
-
-/*
- * Record a preemptible-RCU quiescent state for the specified CPU.  Note
- * that this just means that the task currently running on the CPU is
- * in a quiescent state.  There might be any number of tasks blocked
- * while in an RCU read-side critical section.
- *
- * Unlike the other rcu_*_qs() functions, callers to this function
- * must disable irqs in order to protect the assignment to
- * ->rcu_read_unlock_special.
- *
- * Because this is a single-CPU implementation, the only way a grace
- * period can end is if the CPU is in a quiescent state.  The reason is
- * that a blocked preemptible-RCU reader can exit its critical section
- * only if the CPU is running it at the time.  Therefore, when the
- * last task blocking the current grace period exits its RCU read-side
- * critical section, neither the CPU nor blocked tasks will be stopping
- * the current grace period.  (In contrast, SMP implementations
- * might have CPUs running in RCU read-side critical sections that
- * block later grace periods -- but this is not possible given only
- * one CPU.)
- */
-static void rcu_preempt_cpu_qs(void)
-{
-	/* Record both CPU and task as having responded to current GP. */
-	rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum;
-	current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
-
-	/* If there is no GP then there is nothing more to do.  */
-	if (!rcu_preempt_gp_in_progress())
-		return;
-	/*
-	 * Check up on boosting.  If there are readers blocking the
-	 * current grace period, leave.
-	 */
-	if (rcu_initiate_boost())
-		return;
-
-	/* Advance callbacks. */
-	rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum;
-	rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.rcb.curtail;
-	rcu_preempt_ctrlblk.rcb.curtail = rcu_preempt_ctrlblk.nexttail;
-
-	/* If there are no blocked readers, next GP is done instantly. */
-	if (!rcu_preempt_blocked_readers_any())
-		rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail;
-
-	/* If there are done callbacks, cause them to be invoked. */
-	if (*rcu_preempt_ctrlblk.rcb.donetail != NULL)
-		invoke_rcu_callbacks();
-}
-
-/*
- * Start a new RCU grace period if warranted.  Hard irqs must be disabled.
- */
-static void rcu_preempt_start_gp(void)
-{
-	if (!rcu_preempt_gp_in_progress() && rcu_preempt_needs_another_gp()) {
-
-		/* Official start of GP. */
-		rcu_preempt_ctrlblk.gpnum++;
-		RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++);
-		reset_cpu_stall_ticks(&rcu_preempt_ctrlblk.rcb);
-
-		/* Any blocked RCU readers block new GP. */
-		if (rcu_preempt_blocked_readers_any())
-			rcu_preempt_ctrlblk.gp_tasks =
-				rcu_preempt_ctrlblk.blkd_tasks.next;
-
-		/* Set up for RCU priority boosting. */
-		rcu_preempt_boost_start_gp();
-
-		/* If there is no running reader, CPU is done with GP. */
-		if (!rcu_preempt_running_reader())
-			rcu_preempt_cpu_qs();
-	}
-}
-
-/*
- * We have entered the scheduler, and the current task might soon be
- * context-switched away from.  If this task is in an RCU read-side
- * critical section, we will no longer be able to rely on the CPU to
- * record that fact, so we enqueue the task on the blkd_tasks list.
- * If the task started after the current grace period began, as recorded
- * by ->gpcpu, we enqueue at the beginning of the list.  Otherwise
- * before the element referenced by ->gp_tasks (or at the tail if
- * ->gp_tasks is NULL) and point ->gp_tasks at the newly added element.
- * The task will dequeue itself when it exits the outermost enclosing
- * RCU read-side critical section.  Therefore, the current grace period
- * cannot be permitted to complete until the ->gp_tasks pointer becomes
- * NULL.
- *
- * Caller must disable preemption.
- */
-void rcu_preempt_note_context_switch(void)
-{
-	struct task_struct *t = current;
-	unsigned long flags;
-
-	local_irq_save(flags); /* must exclude scheduler_tick(). */
-	if (rcu_preempt_running_reader() > 0 &&
-	    (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
-
-		/* Possibly blocking in an RCU read-side critical section. */
-		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
-
-		/*
-		 * If this CPU has already checked in, then this task
-		 * will hold up the next grace period rather than the
-		 * current grace period.  Queue the task accordingly.
-		 * If the task is queued for the current grace period
-		 * (i.e., this CPU has not yet passed through a quiescent
-		 * state for the current grace period), then as long
-		 * as that task remains queued, the current grace period
-		 * cannot end.
-		 */
-		list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks);
-		if (rcu_cpu_blocking_cur_gp())
-			rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry;
-	} else if (rcu_preempt_running_reader() < 0 &&
-		   t->rcu_read_unlock_special) {
-		/*
-		 * Complete exit from RCU read-side critical section on
-		 * behalf of preempted instance of __rcu_read_unlock().
-		 */
-		rcu_read_unlock_special(t);
-	}
-
-	/*
-	 * Either we were not in an RCU read-side critical section to
-	 * begin with, or we have now recorded that critical section
-	 * globally.  Either way, we can now note a quiescent state
-	 * for this CPU.  Again, if we were in an RCU read-side critical
-	 * section, and if that critical section was blocking the current
-	 * grace period, then the fact that the task has been enqueued
-	 * means that current grace period continues to be blocked.
-	 */
-	rcu_preempt_cpu_qs();
-	local_irq_restore(flags);
-}
-
-/*
- * Handle special cases during rcu_read_unlock(), such as needing to
- * notify RCU core processing or task having blocked during the RCU
- * read-side critical section.
- */
-void rcu_read_unlock_special(struct task_struct *t)
-{
-	int empty;
-	int empty_exp;
-	unsigned long flags;
-	struct list_head *np;
-#ifdef CONFIG_RCU_BOOST
-	struct rt_mutex *rbmp = NULL;
-#endif /* #ifdef CONFIG_RCU_BOOST */
-	int special;
-
-	/*
-	 * NMI handlers cannot block and cannot safely manipulate state.
-	 * They therefore cannot possibly be special, so just leave.
-	 */
-	if (in_nmi())
-		return;
-
-	local_irq_save(flags);
-
-	/*
-	 * If RCU core is waiting for this CPU to exit critical section,
-	 * let it know that we have done so.
-	 */
-	special = t->rcu_read_unlock_special;
-	if (special & RCU_READ_UNLOCK_NEED_QS)
-		rcu_preempt_cpu_qs();
-
-	/* Hardware IRQ handlers cannot block. */
-	if (in_irq() || in_serving_softirq()) {
-		local_irq_restore(flags);
-		return;
-	}
-
-	/* Clean up if blocked during RCU read-side critical section. */
-	if (special & RCU_READ_UNLOCK_BLOCKED) {
-		t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED;
-
-		/*
-		 * Remove this task from the ->blkd_tasks list and adjust
-		 * any pointers that might have been referencing it.
-		 */
-		empty = !rcu_preempt_blocked_readers_cgp();
-		empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL;
-		np = rcu_next_node_entry(t);
-		list_del_init(&t->rcu_node_entry);
-		if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks)
-			rcu_preempt_ctrlblk.gp_tasks = np;
-		if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks)
-			rcu_preempt_ctrlblk.exp_tasks = np;
-#ifdef CONFIG_RCU_BOOST
-		if (&t->rcu_node_entry == rcu_preempt_ctrlblk.boost_tasks)
-			rcu_preempt_ctrlblk.boost_tasks = np;
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
-		/*
-		 * If this was the last task on the current list, and if
-		 * we aren't waiting on the CPU, report the quiescent state
-		 * and start a new grace period if needed.
-		 */
-		if (!empty && !rcu_preempt_blocked_readers_cgp()) {
-			rcu_preempt_cpu_qs();
-			rcu_preempt_start_gp();
-		}
-
-		/*
-		 * If this was the last task on the expedited lists,
-		 * then we need wake up the waiting task.
-		 */
-		if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL)
-			rcu_report_exp_done();
-	}
-#ifdef CONFIG_RCU_BOOST
-	/* Unboost self if was boosted. */
-	if (t->rcu_boost_mutex != NULL) {
-		rbmp = t->rcu_boost_mutex;
-		t->rcu_boost_mutex = NULL;
-		rt_mutex_unlock(rbmp);
-	}
-#endif /* #ifdef CONFIG_RCU_BOOST */
-	local_irq_restore(flags);
-}
-
-/*
- * Check for a quiescent state from the current CPU.  When a task blocks,
- * the task is recorded in the rcu_preempt_ctrlblk structure, which is
- * checked elsewhere.  This is called from the scheduling-clock interrupt.
- *
- * Caller must disable hard irqs.
- */
-static void rcu_preempt_check_callbacks(void)
-{
-	struct task_struct *t = current;
-
-	if (rcu_preempt_gp_in_progress() &&
-	    (!rcu_preempt_running_reader() ||
-	     !rcu_cpu_blocking_cur_gp()))
-		rcu_preempt_cpu_qs();
-	if (&rcu_preempt_ctrlblk.rcb.rcucblist !=
-	    rcu_preempt_ctrlblk.rcb.donetail)
-		invoke_rcu_callbacks();
-	if (rcu_preempt_gp_in_progress() &&
-	    rcu_cpu_blocking_cur_gp() &&
-	    rcu_preempt_running_reader() > 0)
-		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
-}
-
-/*
- * TINY_PREEMPT_RCU has an extra callback-list tail pointer to
- * update, so this is invoked from rcu_process_callbacks() to
- * handle that case.  Of course, it is invoked for all flavors of
- * RCU, but RCU callbacks can appear only on one of the lists, and
- * neither ->nexttail nor ->donetail can possibly be NULL, so there
- * is no need for an explicit check.
- */
-static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp)
-{
-	if (rcu_preempt_ctrlblk.nexttail == rcp->donetail)
-		rcu_preempt_ctrlblk.nexttail = &rcp->rcucblist;
-}
-
-/*
- * Process callbacks for preemptible RCU.
- */
-static void rcu_preempt_process_callbacks(void)
-{
-	__rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb);
-}
-
-/*
- * Queue a preemptible -RCU callback for invocation after a grace period.
- */
-void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
-{
-	unsigned long flags;
-
-	debug_rcu_head_queue(head);
-	head->func = func;
-	head->next = NULL;
-
-	local_irq_save(flags);
-	*rcu_preempt_ctrlblk.nexttail = head;
-	rcu_preempt_ctrlblk.nexttail = &head->next;
-	RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++);
-	rcu_preempt_start_gp();  /* checks to see if GP needed. */
-	local_irq_restore(flags);
-}
-EXPORT_SYMBOL_GPL(call_rcu);
-
-/*
- * synchronize_rcu - wait until a grace period has elapsed.
- *
- * Control will return to the caller some time after a full grace
- * period has elapsed, in other words after all currently executing RCU
- * read-side critical sections have completed.  RCU read-side critical
- * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
- * and may be nested.
- */
-void synchronize_rcu(void)
-{
-	rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
-			   !lock_is_held(&rcu_lock_map) &&
-			   !lock_is_held(&rcu_sched_lock_map),
-			   "Illegal synchronize_rcu() in RCU read-side critical section");
-
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-	if (!rcu_scheduler_active)
-		return;
-#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
-
-	WARN_ON_ONCE(rcu_preempt_running_reader());
-	if (!rcu_preempt_blocked_readers_any())
-		return;
-
-	/* Once we get past the fastpath checks, same code as rcu_barrier(). */
-	if (rcu_expedited)
-		synchronize_rcu_expedited();
-	else
-		rcu_barrier();
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu);
-
-static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
-static unsigned long sync_rcu_preempt_exp_count;
-static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex);
-
-/*
- * Return non-zero if there are any tasks in RCU read-side critical
- * sections blocking the current preemptible-RCU expedited grace period.
- * If there is no preemptible-RCU expedited grace period currently in
- * progress, returns zero unconditionally.
- */
-static int rcu_preempted_readers_exp(void)
-{
-	return rcu_preempt_ctrlblk.exp_tasks != NULL;
-}
-
-/*
- * Report the exit from RCU read-side critical section for the last task
- * that queued itself during or before the current expedited preemptible-RCU
- * grace period.
- */
-static void rcu_report_exp_done(void)
-{
-	wake_up(&sync_rcu_preempt_exp_wq);
-}
-
-/*
- * Wait for an rcu-preempt grace period, but expedite it.  The basic idea
- * is to rely in the fact that there is but one CPU, and that it is
- * illegal for a task to invoke synchronize_rcu_expedited() while in a
- * preemptible-RCU read-side critical section.  Therefore, any such
- * critical sections must correspond to blocked tasks, which must therefore
- * be on the ->blkd_tasks list.  So just record the current head of the
- * list in the ->exp_tasks pointer, and wait for all tasks including and
- * after the task pointed to by ->exp_tasks to drain.
- */
-void synchronize_rcu_expedited(void)
-{
-	unsigned long flags;
-	struct rcu_preempt_ctrlblk *rpcp = &rcu_preempt_ctrlblk;
-	unsigned long snap;
-
-	barrier(); /* ensure prior action seen before grace period. */
-
-	WARN_ON_ONCE(rcu_preempt_running_reader());
-
-	/*
-	 * Acquire lock so that there is only one preemptible RCU grace
-	 * period in flight.  Of course, if someone does the expedited
-	 * grace period for us while we are acquiring the lock, just leave.
-	 */
-	snap = sync_rcu_preempt_exp_count + 1;
-	mutex_lock(&sync_rcu_preempt_exp_mutex);
-	if (ULONG_CMP_LT(snap, sync_rcu_preempt_exp_count))
-		goto unlock_mb_ret; /* Others did our work for us. */
-
-	local_irq_save(flags);
-
-	/*
-	 * All RCU readers have to already be on blkd_tasks because
-	 * we cannot legally be executing in an RCU read-side critical
-	 * section.
-	 */
-
-	/* Snapshot current head of ->blkd_tasks list. */
-	rpcp->exp_tasks = rpcp->blkd_tasks.next;
-	if (rpcp->exp_tasks == &rpcp->blkd_tasks)
-		rpcp->exp_tasks = NULL;
-
-	/* Wait for tail of ->blkd_tasks list to drain. */
-	if (!rcu_preempted_readers_exp()) {
-		local_irq_restore(flags);
-	} else {
-		rcu_initiate_boost();
-		local_irq_restore(flags);
-		wait_event(sync_rcu_preempt_exp_wq,
-			   !rcu_preempted_readers_exp());
-	}
-
-	/* Clean up and exit. */
-	barrier(); /* ensure expedited GP seen before counter increment. */
-	sync_rcu_preempt_exp_count++;
-unlock_mb_ret:
-	mutex_unlock(&sync_rcu_preempt_exp_mutex);
-	barrier(); /* ensure subsequent action seen after grace period. */
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
-
-/*
- * Does preemptible RCU need the CPU to stay out of dynticks mode?
- */
-int rcu_preempt_needs_cpu(void)
-{
-	return rcu_preempt_ctrlblk.rcb.rcucblist != NULL;
-}
-
-#else /* #ifdef CONFIG_TINY_PREEMPT_RCU */
-
-#ifdef CONFIG_RCU_TRACE
-
-/*
- * Because preemptible RCU does not exist, it is not necessary to
- * dump out its statistics.
- */
-static void show_tiny_preempt_stats(struct seq_file *m)
-{
-}
-
-#endif /* #ifdef CONFIG_RCU_TRACE */
-
-/*
- * Because preemptible RCU does not exist, it never has any callbacks
- * to check.
- */
-static void rcu_preempt_check_callbacks(void)
-{
-}
-
-/*
- * Because preemptible RCU does not exist, it never has any callbacks
- * to remove.
- */
-static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp)
-{
-}
-
-/*
- * Because preemptible RCU does not exist, it never has any callbacks
- * to process.
- */
-static void rcu_preempt_process_callbacks(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */
-
-#ifdef CONFIG_RCU_BOOST
-
-/*
- * Wake up rcu_kthread() to process callbacks now eligible for invocation
- * or to boost readers.
- */
-static void invoke_rcu_callbacks(void)
-{
-	have_rcu_kthread_work = 1;
-	if (rcu_kthread_task != NULL)
-		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
- * RCU_SOFTIRQ that is used for this purpose when boosting is disabled.
- * This is a kthread, but it is never stopped, at least not until
- * the system goes down.
- */
-static int rcu_kthread(void *arg)
-{
-	unsigned long work;
-	unsigned long morework;
-	unsigned long flags;
-
-	for (;;) {
-		wait_event_interruptible(rcu_kthread_wq,
-					 have_rcu_kthread_work != 0);
-		morework = rcu_boost();
-		local_irq_save(flags);
-		work = have_rcu_kthread_work;
-		have_rcu_kthread_work = morework;
-		local_irq_restore(flags);
-		if (work)
-			rcu_process_callbacks(NULL);
-		schedule_timeout_interruptible(1); /* Leave CPU for others. */
-	}
-
-	return 0;  /* Not reached, but needed to shut gcc up. */
-}
-
-/*
- * Spawn the kthread that invokes RCU callbacks.
- */
-static int __init rcu_spawn_kthreads(void)
-{
-	struct sched_param sp;
-
-	rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread");
-	sp.sched_priority = RCU_BOOST_PRIO;
-	sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp);
-	return 0;
-}
-early_initcall(rcu_spawn_kthreads);
-
-#else /* #ifdef CONFIG_RCU_BOOST */
-
-/* Hold off callback invocation until early_initcall() time. */
-static int rcu_scheduler_fully_active __read_mostly;
-
-/*
- * Start up softirq processing of callbacks.
- */
-void invoke_rcu_callbacks(void)
-{
-	if (rcu_scheduler_fully_active)
-		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 */
-
-static int __init rcu_scheduler_really_started(void)
-{
-	rcu_scheduler_fully_active = 1;
-	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
-	raise_softirq(RCU_SOFTIRQ);  /* Invoke any callbacks from early boot. */
-	return 0;
-}
-early_initcall(rcu_scheduler_really_started);
-
-#endif /* #else #ifdef CONFIG_RCU_BOOST */
-
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-#include <linux/kernel_stat.h>
 
 /*
  * During boot, we forgive RCU lockdep issues.  After this function is
@@ -1020,25 +72,6 @@ void __init rcu_scheduler_starting(void)
 
 #ifdef CONFIG_RCU_TRACE
 
-#ifdef CONFIG_RCU_BOOST
-
-static void rcu_initiate_boost_trace(void)
-{
-	if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks))
-		rcu_preempt_ctrlblk.n_balk_blkd_tasks++;
-	else if (rcu_preempt_ctrlblk.gp_tasks == NULL &&
-		 rcu_preempt_ctrlblk.exp_tasks == NULL)
-		rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++;
-	else if (rcu_preempt_ctrlblk.boost_tasks != NULL)
-		rcu_preempt_ctrlblk.n_balk_boost_tasks++;
-	else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time))
-		rcu_preempt_ctrlblk.n_balk_notyet++;
-	else
-		rcu_preempt_ctrlblk.n_balk_nos++;
-}
-
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
 static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
 {
 	unsigned long flags;
@@ -1053,7 +86,6 @@ static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
  */
 static int show_tiny_stats(struct seq_file *m, void *unused)
 {
-	show_tiny_preempt_stats(m);
 	seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen);
 	seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen);
 	return 0;
@@ -1103,11 +135,40 @@ MODULE_AUTHOR("Paul E. McKenney");
 MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation");
 MODULE_LICENSE("GPL");
 
-static void check_cpu_stall_preempt(void)
+static void check_cpu_stall(struct rcu_ctrlblk *rcp)
 {
-#ifdef CONFIG_TINY_PREEMPT_RCU
-	check_cpu_stall(&rcu_preempt_ctrlblk.rcb);
-#endif /* #ifdef CONFIG_TINY_PREEMPT_RCU */
+	unsigned long j;
+	unsigned long js;
+
+	if (rcu_cpu_stall_suppress)
+		return;
+	rcp->ticks_this_gp++;
+	j = jiffies;
+	js = rcp->jiffies_stall;
+	if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
+		pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
+		       rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
+		       jiffies - rcp->gp_start, rcp->qlen);
+		dump_stack();
+	}
+	if (*rcp->curtail && ULONG_CMP_GE(j, js))
+		rcp->jiffies_stall = jiffies +
+			3 * rcu_jiffies_till_stall_check() + 3;
+	else if (ULONG_CMP_GE(j, js))
+		rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
+}
+
+static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
+{
+	rcp->ticks_this_gp = 0;
+	rcp->gp_start = jiffies;
+	rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
+}
+
+static void check_cpu_stalls(void)
+{
+	RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
+	RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
 }
 
 #endif /* #ifdef CONFIG_RCU_TRACE */
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index e1f3a8c96724..b1fa5510388d 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -695,44 +695,6 @@ static struct rcu_torture_ops srcu_sync_ops = {
 	.name		= "srcu_sync"
 };
 
-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		= rcu_sync_torture_init,
-	.readlock	= srcu_torture_read_lock_raw,
-	.read_delay	= srcu_read_delay,
-	.readunlock	= srcu_torture_read_unlock_raw,
-	.completed	= srcu_torture_completed,
-	.deferred_free	= srcu_torture_deferred_free,
-	.sync		= srcu_torture_synchronize,
-	.call		= NULL,
-	.cb_barrier	= NULL,
-	.stats		= srcu_torture_stats,
-	.name		= "srcu_raw"
-};
-
-static struct rcu_torture_ops srcu_raw_sync_ops = {
-	.init		= rcu_sync_torture_init,
-	.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,
-	.call		= NULL,
-	.cb_barrier	= NULL,
-	.stats		= srcu_torture_stats,
-	.name		= "srcu_raw_sync"
-};
-
 static void srcu_torture_synchronize_expedited(void)
 {
 	synchronize_srcu_expedited(&srcu_ctl);
@@ -1983,7 +1945,6 @@ rcu_torture_init(void)
 		{ &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
 		  &rcu_bh_ops, &rcu_bh_sync_ops, &rcu_bh_expedited_ops,
 		  &srcu_ops, &srcu_sync_ops, &srcu_expedited_ops,
-		  &srcu_raw_ops, &srcu_raw_sync_ops,
 		  &sched_ops, &sched_sync_ops, &sched_expedited_ops, };
 
 	mutex_lock(&fullstop_mutex);
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 35380019f0fc..cf3adc6fe001 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -218,8 +218,8 @@ module_param(blimit, long, 0444);
 module_param(qhimark, long, 0444);
 module_param(qlowmark, long, 0444);
 
-static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS;
-static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
+static ulong jiffies_till_first_fqs = ULONG_MAX;
+static ulong jiffies_till_next_fqs = ULONG_MAX;
 
 module_param(jiffies_till_first_fqs, ulong, 0644);
 module_param(jiffies_till_next_fqs, ulong, 0644);
@@ -866,7 +866,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
 	 * See Documentation/RCU/stallwarn.txt for info on how to debug
 	 * RCU CPU stall warnings.
 	 */
-	printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:",
+	pr_err("INFO: %s detected stalls on CPUs/tasks:",
 	       rsp->name);
 	print_cpu_stall_info_begin();
 	rcu_for_each_leaf_node(rsp, rnp) {
@@ -899,7 +899,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
 	       smp_processor_id(), (long)(jiffies - rsp->gp_start),
 	       rsp->gpnum, rsp->completed, totqlen);
 	if (ndetected == 0)
-		printk(KERN_ERR "INFO: Stall ended before state dump start\n");
+		pr_err("INFO: Stall ended before state dump start\n");
 	else if (!trigger_all_cpu_backtrace())
 		rcu_dump_cpu_stacks(rsp);
 
@@ -922,7 +922,7 @@ static void print_cpu_stall(struct rcu_state *rsp)
 	 * See Documentation/RCU/stallwarn.txt for info on how to debug
 	 * RCU CPU stall warnings.
 	 */
-	printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name);
+	pr_err("INFO: %s self-detected stall on CPU", rsp->name);
 	print_cpu_stall_info_begin();
 	print_cpu_stall_info(rsp, smp_processor_id());
 	print_cpu_stall_info_end();
@@ -985,65 +985,6 @@ void rcu_cpu_stall_reset(void)
 }
 
 /*
- * Update CPU-local rcu_data state to record the newly noticed grace period.
- * This is used both when we started the grace period and when we notice
- * that someone else started the grace period.  The caller must hold the
- * ->lock of the leaf rcu_node structure corresponding to the current CPU,
- *  and must have irqs disabled.
- */
-static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
-{
-	if (rdp->gpnum != rnp->gpnum) {
-		/*
-		 * If the current grace period is waiting for this CPU,
-		 * set up to detect a quiescent state, otherwise don't
-		 * go looking for one.
-		 */
-		rdp->gpnum = rnp->gpnum;
-		trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
-		rdp->passed_quiesce = 0;
-		rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
-		zero_cpu_stall_ticks(rdp);
-	}
-}
-
-static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
-{
-	unsigned long flags;
-	struct rcu_node *rnp;
-
-	local_irq_save(flags);
-	rnp = rdp->mynode;
-	if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */
-	    !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
-		local_irq_restore(flags);
-		return;
-	}
-	__note_new_gpnum(rsp, rnp, rdp);
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-}
-
-/*
- * Did someone else start a new RCU grace period start since we last
- * checked?  Update local state appropriately if so.  Must be called
- * on the CPU corresponding to rdp.
- */
-static int
-check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
-{
-	unsigned long flags;
-	int ret = 0;
-
-	local_irq_save(flags);
-	if (rdp->gpnum != rsp->gpnum) {
-		note_new_gpnum(rsp, rdp);
-		ret = 1;
-	}
-	local_irq_restore(flags);
-	return ret;
-}
-
-/*
  * Initialize the specified rcu_data structure's callback list to empty.
  */
 static void init_callback_list(struct rcu_data *rdp)
@@ -1313,18 +1254,16 @@ static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
 }
 
 /*
- * Advance this CPU's callbacks, but only if the current grace period
- * has ended.  This may be called only from the CPU to whom the rdp
- * belongs.  In addition, the corresponding leaf rcu_node structure's
- * ->lock must be held by the caller, with irqs disabled.
+ * Update CPU-local rcu_data state to record the beginnings and ends of
+ * grace periods.  The caller must hold the ->lock of the leaf rcu_node
+ * structure corresponding to the current CPU, and must have irqs disabled.
  */
-static void
-__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
+static void __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
 {
-	/* Did another grace period end? */
+	/* Handle the ends of any preceding grace periods first. */
 	if (rdp->completed == rnp->completed) {
 
-		/* No, so just accelerate recent callbacks. */
+		/* No grace period end, so just accelerate recent callbacks. */
 		rcu_accelerate_cbs(rsp, rnp, rdp);
 
 	} else {
@@ -1335,68 +1274,40 @@ __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat
 		/* Remember that we saw this grace-period completion. */
 		rdp->completed = rnp->completed;
 		trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend");
+	}
 
+	if (rdp->gpnum != rnp->gpnum) {
 		/*
-		 * If we were in an extended quiescent state, we may have
-		 * missed some grace periods that others CPUs handled on
-		 * our behalf. Catch up with this state to avoid noting
-		 * spurious new grace periods.  If another grace period
-		 * has started, then rnp->gpnum will have advanced, so
-		 * we will detect this later on.  Of course, any quiescent
-		 * states we found for the old GP are now invalid.
-		 */
-		if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) {
-			rdp->gpnum = rdp->completed;
-			rdp->passed_quiesce = 0;
-		}
-
-		/*
-		 * If RCU does not need a quiescent state from this CPU,
-		 * then make sure that this CPU doesn't go looking for one.
+		 * If the current grace period is waiting for this CPU,
+		 * set up to detect a quiescent state, otherwise don't
+		 * go looking for one.
 		 */
-		if ((rnp->qsmask & rdp->grpmask) == 0)
-			rdp->qs_pending = 0;
+		rdp->gpnum = rnp->gpnum;
+		trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
+		rdp->passed_quiesce = 0;
+		rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
+		zero_cpu_stall_ticks(rdp);
 	}
 }
 
-/*
- * Advance this CPU's callbacks, but only if the current grace period
- * has ended.  This may be called only from the CPU to whom the rdp
- * belongs.
- */
-static void
-rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
+static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
 {
 	unsigned long flags;
 	struct rcu_node *rnp;
 
 	local_irq_save(flags);
 	rnp = rdp->mynode;
-	if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */
+	if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) &&
+	     rdp->completed == ACCESS_ONCE(rnp->completed)) || /* w/out lock. */
 	    !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
 		local_irq_restore(flags);
 		return;
 	}
-	__rcu_process_gp_end(rsp, rnp, rdp);
+	__note_gp_changes(rsp, rnp, rdp);
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 }
 
 /*
- * Do per-CPU grace-period initialization for running CPU.  The caller
- * must hold the lock of the leaf rcu_node structure corresponding to
- * this CPU.
- */
-static void
-rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
-{
-	/* Prior grace period ended, so advance callbacks for current CPU. */
-	__rcu_process_gp_end(rsp, rnp, rdp);
-
-	/* Set state so that this CPU will detect the next quiescent state. */
-	__note_new_gpnum(rsp, rnp, rdp);
-}
-
-/*
  * Initialize a new grace period.
  */
 static int rcu_gp_init(struct rcu_state *rsp)
@@ -1444,7 +1355,7 @@ static int rcu_gp_init(struct rcu_state *rsp)
 		WARN_ON_ONCE(rnp->completed != rsp->completed);
 		ACCESS_ONCE(rnp->completed) = rsp->completed;
 		if (rnp == rdp->mynode)
-			rcu_start_gp_per_cpu(rsp, rnp, rdp);
+			__note_gp_changes(rsp, rnp, rdp);
 		rcu_preempt_boost_start_gp(rnp);
 		trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
 					    rnp->level, rnp->grplo,
@@ -1527,7 +1438,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
 		ACCESS_ONCE(rnp->completed) = rsp->gpnum;
 		rdp = this_cpu_ptr(rsp->rda);
 		if (rnp == rdp->mynode)
-			__rcu_process_gp_end(rsp, rnp, rdp);
+			__note_gp_changes(rsp, rnp, rdp);
 		nocb += rcu_future_gp_cleanup(rsp, rnp);
 		raw_spin_unlock_irq(&rnp->lock);
 		cond_resched();
@@ -1805,9 +1716,8 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
 static void
 rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
 {
-	/* If there is now a new grace period, record and return. */
-	if (check_for_new_grace_period(rsp, rdp))
-		return;
+	/* Check for grace-period ends and beginnings. */
+	note_gp_changes(rsp, rdp);
 
 	/*
 	 * Does this CPU still need to do its part for current grace period?
@@ -2271,9 +2181,6 @@ __rcu_process_callbacks(struct rcu_state *rsp)
 
 	WARN_ON_ONCE(rdp->beenonline == 0);
 
-	/* Handle the end of a grace period that some other CPU ended.  */
-	rcu_process_gp_end(rsp, rdp);
-
 	/* Update RCU state based on any recent quiescent states. */
 	rcu_check_quiescent_state(rsp, rdp);
 
@@ -2358,8 +2265,7 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
 	if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
 
 		/* Are we ignoring a completed grace period? */
-		rcu_process_gp_end(rsp, rdp);
-		check_for_new_grace_period(rsp, rdp);
+		note_gp_changes(rsp, rdp);
 
 		/* Start a new grace period if one not already started. */
 		if (!rcu_gp_in_progress(rsp)) {
@@ -3265,11 +3171,25 @@ static void __init rcu_init_one(struct rcu_state *rsp,
  */
 static void __init rcu_init_geometry(void)
 {
+	ulong d;
 	int i;
 	int j;
 	int n = nr_cpu_ids;
 	int rcu_capacity[MAX_RCU_LVLS + 1];
 
+	/*
+	 * Initialize any unspecified boot parameters.
+	 * The default values of jiffies_till_first_fqs and
+	 * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS
+	 * value, which is a function of HZ, then adding one for each
+	 * RCU_JIFFIES_FQS_DIV CPUs that might be on the system.
+	 */
+	d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
+	if (jiffies_till_first_fqs == ULONG_MAX)
+		jiffies_till_first_fqs = d;
+	if (jiffies_till_next_fqs == ULONG_MAX)
+		jiffies_till_next_fqs = d;
+
 	/* If the compile-time values are accurate, just leave. */
 	if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF &&
 	    nr_cpu_ids == NR_CPUS)
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 4df503470e42..4a39d364493c 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -343,12 +343,17 @@ struct rcu_data {
 #define RCU_FORCE_QS		3	/* Need to force quiescent state. */
 #define RCU_SIGNAL_INIT		RCU_SAVE_DYNTICK
 
-#define RCU_JIFFIES_TILL_FORCE_QS	 3	/* for rsp->jiffies_force_qs */
+#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
+					/* For jiffies_till_first_fqs and */
+					/*  and jiffies_till_next_fqs. */
 
-#define RCU_STALL_RAT_DELAY		2	/* Allow other CPUs time */
-						/*  to take at least one */
-						/*  scheduling clock irq */
-						/*  before ratting on them. */
+#define RCU_JIFFIES_FQS_DIV	256	/* Very large systems need more */
+					/*  delay between bouts of */
+					/*  quiescent-state forcing. */
+
+#define RCU_STALL_RAT_DELAY	2	/* Allow other CPUs time to take */
+					/*  at least one scheduling clock */
+					/*  irq before ratting on them. */
 
 #define rcu_wait(cond)							\
 do {									\
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 3db5a375d8dd..63098a59216e 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -53,38 +53,37 @@ static char __initdata nocb_buf[NR_CPUS * 5];
 static void __init rcu_bootup_announce_oddness(void)
 {
 #ifdef CONFIG_RCU_TRACE
-	printk(KERN_INFO "\tRCU debugfs-based tracing is enabled.\n");
+	pr_info("\tRCU debugfs-based tracing is enabled.\n");
 #endif
 #if (defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || (!defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32)
-	printk(KERN_INFO "\tCONFIG_RCU_FANOUT set to non-default value of %d\n",
+	pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n",
 	       CONFIG_RCU_FANOUT);
 #endif
 #ifdef CONFIG_RCU_FANOUT_EXACT
-	printk(KERN_INFO "\tHierarchical RCU autobalancing is disabled.\n");
+	pr_info("\tHierarchical RCU autobalancing is disabled.\n");
 #endif
 #ifdef CONFIG_RCU_FAST_NO_HZ
-	printk(KERN_INFO
-	       "\tRCU dyntick-idle grace-period acceleration is enabled.\n");
+	pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
 #endif
 #ifdef CONFIG_PROVE_RCU
-	printk(KERN_INFO "\tRCU lockdep checking is enabled.\n");
+	pr_info("\tRCU lockdep checking is enabled.\n");
 #endif
 #ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE
-	printk(KERN_INFO "\tRCU torture testing starts during boot.\n");
+	pr_info("\tRCU torture testing starts during boot.\n");
 #endif
 #if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE)
-	printk(KERN_INFO "\tDump stacks of tasks blocking RCU-preempt GP.\n");
+	pr_info("\tDump stacks of tasks blocking RCU-preempt GP.\n");
 #endif
 #if defined(CONFIG_RCU_CPU_STALL_INFO)
-	printk(KERN_INFO "\tAdditional per-CPU info printed with stalls.\n");
+	pr_info("\tAdditional per-CPU info printed with stalls.\n");
 #endif
 #if NUM_RCU_LVL_4 != 0
-	printk(KERN_INFO "\tFour-level hierarchy is enabled.\n");
+	pr_info("\tFour-level hierarchy is enabled.\n");
 #endif
 	if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF)
-		printk(KERN_INFO "\tExperimental boot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
+		pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
 	if (nr_cpu_ids != NR_CPUS)
-		printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
+		pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
 #ifdef CONFIG_RCU_NOCB_CPU
 #ifndef CONFIG_RCU_NOCB_CPU_NONE
 	if (!have_rcu_nocb_mask) {
@@ -92,19 +91,19 @@ static void __init rcu_bootup_announce_oddness(void)
 		have_rcu_nocb_mask = true;
 	}
 #ifdef CONFIG_RCU_NOCB_CPU_ZERO
-	pr_info("\tExperimental no-CBs CPU 0\n");
+	pr_info("\tOffload RCU callbacks from CPU 0\n");
 	cpumask_set_cpu(0, rcu_nocb_mask);
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */
 #ifdef CONFIG_RCU_NOCB_CPU_ALL
-	pr_info("\tExperimental no-CBs for all CPUs\n");
+	pr_info("\tOffload RCU callbacks from all CPUs\n");
 	cpumask_setall(rcu_nocb_mask);
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
 #endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */
 	if (have_rcu_nocb_mask) {
 		cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask);
-		pr_info("\tExperimental no-CBs CPUs: %s.\n", nocb_buf);
+		pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf);
 		if (rcu_nocb_poll)
-			pr_info("\tExperimental polled no-CBs CPUs.\n");
+			pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
 	}
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 }
@@ -123,7 +122,7 @@ static int rcu_preempted_readers_exp(struct rcu_node *rnp);
  */
 static void __init rcu_bootup_announce(void)
 {
-	printk(KERN_INFO "Preemptible hierarchical RCU implementation.\n");
+	pr_info("Preemptible hierarchical RCU implementation.\n");
 	rcu_bootup_announce_oddness();
 }
 
@@ -490,13 +489,13 @@ static void rcu_print_detail_task_stall(struct rcu_state *rsp)
 
 static void rcu_print_task_stall_begin(struct rcu_node *rnp)
 {
-	printk(KERN_ERR "\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
+	pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
 	       rnp->level, rnp->grplo, rnp->grphi);
 }
 
 static void rcu_print_task_stall_end(void)
 {
-	printk(KERN_CONT "\n");
+	pr_cont("\n");
 }
 
 #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
@@ -526,7 +525,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
 	t = list_entry(rnp->gp_tasks,
 		       struct task_struct, rcu_node_entry);
 	list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
-		printk(KERN_CONT " P%d", t->pid);
+		pr_cont(" P%d", t->pid);
 		ndetected++;
 	}
 	rcu_print_task_stall_end();
@@ -933,6 +932,24 @@ static void __init __rcu_init_preempt(void)
 	rcu_init_one(&rcu_preempt_state, &rcu_preempt_data);
 }
 
+/*
+ * Check for a task exiting while in a preemptible-RCU read-side
+ * critical section, clean up if so.  No need to issue warnings,
+ * as debug_check_no_locks_held() already does this if lockdep
+ * is enabled.
+ */
+void exit_rcu(void)
+{
+	struct task_struct *t = current;
+
+	if (likely(list_empty(&current->rcu_node_entry)))
+		return;
+	t->rcu_read_lock_nesting = 1;
+	barrier();
+	t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
+	__rcu_read_unlock();
+}
+
 #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
 
 static struct rcu_state *rcu_state = &rcu_sched_state;
@@ -942,7 +959,7 @@ static struct rcu_state *rcu_state = &rcu_sched_state;
  */
 static void __init rcu_bootup_announce(void)
 {
-	printk(KERN_INFO "Hierarchical RCU implementation.\n");
+	pr_info("Hierarchical RCU implementation.\n");
 	rcu_bootup_announce_oddness();
 }
 
@@ -1101,6 +1118,14 @@ static void __init __rcu_init_preempt(void)
 {
 }
 
+/*
+ * Because preemptible RCU does not exist, tasks cannot possibly exit
+ * while in preemptible RCU read-side critical sections.
+ */
+void exit_rcu(void)
+{
+}
+
 #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
 
 #ifdef CONFIG_RCU_BOOST
@@ -1629,7 +1654,7 @@ static bool rcu_try_advance_all_cbs(void)
 		 */
 		if (rdp->completed != rnp->completed &&
 		    rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL])
-			rcu_process_gp_end(rsp, rdp);
+			note_gp_changes(rsp, rdp);
 
 		if (cpu_has_callbacks_ready_to_invoke(rdp))
 			cbs_ready = true;
@@ -1883,7 +1908,7 @@ static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
 /* Initiate the stall-info list. */
 static void print_cpu_stall_info_begin(void)
 {
-	printk(KERN_CONT "\n");
+	pr_cont("\n");
 }
 
 /*
@@ -1914,7 +1939,7 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
 		ticks_value = rsp->gpnum - rdp->gpnum;
 	}
 	print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
-	printk(KERN_ERR "\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s\n",
+	pr_err("\t%d: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u %s\n",
 	       cpu, ticks_value, ticks_title,
 	       atomic_read(&rdtp->dynticks) & 0xfff,
 	       rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting,
@@ -1925,7 +1950,7 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
 /* Terminate the stall-info list. */
 static void print_cpu_stall_info_end(void)
 {
-	printk(KERN_ERR "\t");
+	pr_err("\t");
 }
 
 /* Zero ->ticks_this_gp for all flavors of RCU. */
@@ -1948,17 +1973,17 @@ static void increment_cpu_stall_ticks(void)
 
 static void print_cpu_stall_info_begin(void)
 {
-	printk(KERN_CONT " {");
+	pr_cont(" {");
 }
 
 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
 {
-	printk(KERN_CONT " %d", cpu);
+	pr_cont(" %d", cpu);
 }
 
 static void print_cpu_stall_info_end(void)
 {
-	printk(KERN_CONT "} ");
+	pr_cont("} ");
 }
 
 static void zero_cpu_stall_ticks(struct rcu_data *rdp)