diff --git a/ap/os/linux/linux-3.4.x/kernel/rcutree.c b/ap/os/linux/linux-3.4.x/kernel/rcutree.c
new file mode 100644
index 0000000..055268b
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/kernel/rcutree.c
@@ -0,0 +1,2547 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Authors: Dipankar Sarma <dipankar@in.ibm.com>
+ *	    Manfred Spraul <manfred@colorfullife.com>
+ *	    Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version
+ *
+ * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
+ * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ *	Documentation/RCU
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/nmi.h>
+#include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/export.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/mutex.h>
+#include <linux/time.h>
+#include <linux/kernel_stat.h>
+#include <linux/wait.h>
+#include <linux/kthread.h>
+#include <linux/prefetch.h>
+#include <linux/delay.h>
+#include <linux/stop_machine.h>
+
+#include "rcutree.h"
+#include <trace/events/rcu.h>
+
+#include "rcu.h"
+
+/* Data structures. */
+
+static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
+
+#define RCU_STATE_INITIALIZER(structname) { \
+	.level = { &structname##_state.node[0] }, \
+	.levelcnt = { \
+		NUM_RCU_LVL_0,  /* root of hierarchy. */ \
+		NUM_RCU_LVL_1, \
+		NUM_RCU_LVL_2, \
+		NUM_RCU_LVL_3, \
+		NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \
+	}, \
+	.fqs_state = RCU_GP_IDLE, \
+	.gpnum = -300, \
+	.completed = -300, \
+	.onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.onofflock), \
+	.fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.fqslock), \
+	.n_force_qs = 0, \
+	.n_force_qs_ngp = 0, \
+	.name = #structname, \
+}
+
+struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched);
+DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
+
+struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh);
+DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
+
+static struct rcu_state *rcu_state;
+
+/*
+ * The rcu_scheduler_active variable transitions from zero to one just
+ * before the first task is spawned.  So when this variable is zero, RCU
+ * can assume that there is but one task, allowing RCU to (for example)
+ * optimized synchronize_sched() to a simple barrier().  When this variable
+ * is one, RCU must actually do all the hard work required to detect real
+ * grace periods.  This variable is also used to suppress boot-time false
+ * positives from lockdep-RCU error checking.
+ */
+int rcu_scheduler_active __read_mostly;
+EXPORT_SYMBOL_GPL(rcu_scheduler_active);
+
+/*
+ * The rcu_scheduler_fully_active variable transitions from zero to one
+ * during the early_initcall() processing, which is after the scheduler
+ * is capable of creating new tasks.  So RCU processing (for example,
+ * creating tasks for RCU priority boosting) must be delayed until after
+ * rcu_scheduler_fully_active transitions from zero to one.  We also
+ * currently delay invocation of any RCU callbacks until after this point.
+ *
+ * It might later prove better for people registering RCU callbacks during
+ * early boot to take responsibility for these callbacks, but one step at
+ * a time.
+ */
+static int rcu_scheduler_fully_active __read_mostly;
+
+#ifdef CONFIG_RCU_BOOST
+
+/*
+ * Control variables for per-CPU and per-rcu_node kthreads.  These
+ * handle all flavors of RCU.
+ */
+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 */
+
+static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
+static void invoke_rcu_core(void);
+static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
+
+/*
+ * Track the rcutorture test sequence number and the update version
+ * number within a given test.  The rcutorture_testseq is incremented
+ * on every rcutorture module load and unload, so has an odd value
+ * when a test is running.  The rcutorture_vernum is set to zero
+ * when rcutorture starts and is incremented on each rcutorture update.
+ * These variables enable correlating rcutorture output with the
+ * RCU tracing information.
+ */
+unsigned long rcutorture_testseq;
+unsigned long rcutorture_vernum;
+
+/*
+ * Return true if an RCU grace period is in progress.  The ACCESS_ONCE()s
+ * permit this function to be invoked without holding the root rcu_node
+ * structure's ->lock, but of course results can be subject to change.
+ */
+static int rcu_gp_in_progress(struct rcu_state *rsp)
+{
+	return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
+}
+
+/*
+ * Note a quiescent state.  Because we do not need to know
+ * how many quiescent states passed, just if there was at least
+ * one since the start of the grace period, this just sets a flag.
+ * The caller must have disabled preemption.
+ */
+void rcu_sched_qs(int cpu)
+{
+	struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
+
+	rdp->passed_quiesce_gpnum = rdp->gpnum;
+	barrier();
+	if (rdp->passed_quiesce == 0)
+		trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
+	rdp->passed_quiesce = 1;
+}
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+static void rcu_preempt_qs(int cpu);
+
+void rcu_bh_qs(int cpu)
+{
+	unsigned long flags;
+
+	/* Callers to this function, rcu_preempt_qs(), must disable irqs. */
+	local_irq_save(flags);
+	rcu_preempt_qs(cpu);
+	local_irq_restore(flags);
+}
+#else
+void rcu_bh_qs(int cpu)
+{
+	struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
+
+	rdp->passed_quiesce_gpnum = rdp->gpnum;
+	barrier();
+	if (rdp->passed_quiesce == 0)
+		trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
+	rdp->passed_quiesce = 1;
+}
+#endif
+
+/*
+ * Note a context switch.  This is a quiescent state for RCU-sched,
+ * and requires special handling for preemptible RCU.
+ * The caller must have disabled preemption.
+ */
+void rcu_note_context_switch(int cpu)
+{
+	trace_rcu_utilization("Start context switch");
+	rcu_sched_qs(cpu);
+	rcu_preempt_note_context_switch(cpu);
+	trace_rcu_utilization("End context switch");
+}
+EXPORT_SYMBOL_GPL(rcu_note_context_switch);
+
+DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
+	.dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
+	.dynticks = ATOMIC_INIT(1),
+};
+
+static long blimit = 10;	/* Maximum callbacks per rcu_do_batch. */
+static long qhimark = 10000;	/* If this many pending, ignore blimit. */
+static long qlowmark = 100;	/* Once only this many pending, use blimit. */
+
+module_param(blimit, long, 0);
+module_param(qhimark, long, 0);
+module_param(qlowmark, long, 0);
+
+int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
+int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
+
+module_param(rcu_cpu_stall_suppress, int, 0644);
+module_param(rcu_cpu_stall_timeout, int, 0644);
+
+static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
+static int rcu_pending(int cpu);
+
+/*
+ * Return the number of RCU-sched batches processed thus far for debug & stats.
+ */
+long rcu_batches_completed_sched(void)
+{
+	return rcu_sched_state.completed;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
+
+#ifndef CONFIG_PREEMPT_RT_FULL
+/*
+ * Return the number of RCU BH batches processed thus far for debug & stats.
+ */
+long rcu_batches_completed_bh(void)
+{
+	return rcu_bh_state.completed;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
+
+/*
+ * Force a quiescent state for RCU BH.
+ */
+void rcu_bh_force_quiescent_state(void)
+{
+	force_quiescent_state(&rcu_bh_state, 0);
+}
+EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
+#endif
+
+/*
+ * Record the number of times rcutorture tests have been initiated and
+ * terminated.  This information allows the debugfs tracing stats to be
+ * correlated to the rcutorture messages, even when the rcutorture module
+ * is being repeatedly loaded and unloaded.  In other words, we cannot
+ * store this state in rcutorture itself.
+ */
+void rcutorture_record_test_transition(void)
+{
+	rcutorture_testseq++;
+	rcutorture_vernum = 0;
+}
+EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
+
+/*
+ * Record the number of writer passes through the current rcutorture test.
+ * This is also used to correlate debugfs tracing stats with the rcutorture
+ * messages.
+ */
+void rcutorture_record_progress(unsigned long vernum)
+{
+	rcutorture_vernum++;
+}
+EXPORT_SYMBOL_GPL(rcutorture_record_progress);
+
+/*
+ * Force a quiescent state for RCU-sched.
+ */
+void rcu_sched_force_quiescent_state(void)
+{
+	force_quiescent_state(&rcu_sched_state, 0);
+}
+EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
+
+/*
+ * Does the CPU have callbacks ready to be invoked?
+ */
+static int
+cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
+{
+	return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL];
+}
+
+/*
+ * Does the current CPU require a yet-as-unscheduled grace period?
+ */
+static int
+cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+	return *rdp->nxttail[RCU_DONE_TAIL +
+			     ACCESS_ONCE(rsp->completed) != rdp->completed] &&
+	       !rcu_gp_in_progress(rsp);
+}
+
+/*
+ * Return the root node of the specified rcu_state structure.
+ */
+static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
+{
+	return &rsp->node[0];
+}
+
+/*
+ * If the specified CPU is offline, tell the caller that it is in
+ * a quiescent state.  Otherwise, whack it with a reschedule IPI.
+ * Grace periods can end up waiting on an offline CPU when that
+ * CPU is in the process of coming online -- it will be added to the
+ * rcu_node bitmasks before it actually makes it online.  The same thing
+ * can happen while a CPU is in the process of coming online.  Because this
+ * race is quite rare, we check for it after detecting that the grace
+ * period has been delayed rather than checking each and every CPU
+ * each and every time we start a new grace period.
+ */
+static int rcu_implicit_offline_qs(struct rcu_data *rdp)
+{
+	/*
+	 * If the CPU is offline for more than a jiffy, it is in a quiescent
+	 * state.  We can trust its state not to change because interrupts
+	 * are disabled.  The reason for the jiffy's worth of slack is to
+	 * handle CPUs initializing on the way up and finding their way
+	 * to the idle loop on the way down.
+	 */
+	if (cpu_is_offline(rdp->cpu) &&
+	    ULONG_CMP_LT(rdp->rsp->gp_start + 2, jiffies)) {
+		trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl");
+		rdp->offline_fqs++;
+		return 1;
+	}
+	return 0;
+}
+
+/*
+ * 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);
+
+	/*
+	 * The idle task is not permitted to enter the idle loop while
+	 * in an RCU read-side critical section.
+	 */
+	rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
+			   "Illegal idle entry in RCU read-side critical section.");
+	rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),
+			   "Illegal idle entry in RCU-bh read-side critical section.");
+	rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),
+			   "Illegal idle entry in RCU-sched read-side critical section.");
+}
+
+/**
+ * rcu_idle_enter - inform RCU that current CPU is entering idle
+ *
+ * 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 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_idle_enter(void)
+{
+	unsigned long flags;
+	long long oldval;
+	struct rcu_dynticks *rdtp;
+
+	local_irq_save(flags);
+	rdtp = &__get_cpu_var(rcu_dynticks);
+	oldval = rdtp->dynticks_nesting;
+	WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
+	if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE)
+		rdtp->dynticks_nesting = 0;
+	else
+		rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
+	rcu_idle_enter_common(rdtp, oldval);
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_idle_enter);
+
+/**
+ * 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.
+ *
+ * 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_irq_exit(void)
+{
+	unsigned long flags;
+	long long oldval;
+	struct rcu_dynticks *rdtp;
+
+	local_irq_save(flags);
+	rdtp = &__get_cpu_var(rcu_dynticks);
+	oldval = rdtp->dynticks_nesting;
+	rdtp->dynticks_nesting--;
+	WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
+	if (rdtp->dynticks_nesting)
+		trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting);
+	else
+		rcu_idle_enter_common(rdtp, oldval);
+	local_irq_restore(flags);
+}
+
+/*
+ * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle
+ *
+ * If the new value of the ->dynticks_nesting counter was previously zero,
+ * we really have exited idle, and must do the appropriate accounting.
+ * The caller must have disabled interrupts.
+ */
+static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
+{
+	smp_mb__before_atomic_inc();  /* Force ordering w/previous sojourn. */
+	atomic_inc(&rdtp->dynticks);
+	/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
+	smp_mb__after_atomic_inc();  /* See above. */
+	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
+	rcu_cleanup_after_idle(smp_processor_id());
+	trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
+	if (!is_idle_task(current)) {
+		struct task_struct *idle = idle_task(smp_processor_id());
+
+		trace_rcu_dyntick("Error on exit: not idle task",
+				  oldval, rdtp->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_idle_exit - inform RCU that current CPU is leaving idle
+ *
+ * Exit idle mode, in other words, -enter- the mode in which RCU
+ * read-side critical sections can occur.
+ *
+ * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to
+ * allow for the possibility of usermode upcalls messing up our count
+ * of interrupt nesting level during the busy period that is just
+ * now starting.
+ */
+void rcu_idle_exit(void)
+{
+	unsigned long flags;
+	struct rcu_dynticks *rdtp;
+	long long oldval;
+
+	local_irq_save(flags);
+	rdtp = &__get_cpu_var(rcu_dynticks);
+	oldval = rdtp->dynticks_nesting;
+	WARN_ON_ONCE(oldval < 0);
+	if (oldval & DYNTICK_TASK_NEST_MASK)
+		rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
+	else
+		rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+	rcu_idle_exit_common(rdtp, oldval);
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
+
+/**
+ * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
+ *
+ * Enter an interrupt handler, which might possibly result in exiting
+ * idle mode, in other words, entering the mode in which read-side critical
+ * sections can occur.
+ *
+ * Note that the Linux kernel is fully capable of entering an interrupt
+ * handler that it never exits, for example when doing upcalls to
+ * user mode!  This code assumes that the idle loop never does upcalls to
+ * user mode.  If your architecture does do upcalls from the idle loop (or
+ * does anything else that results in unbalanced calls to the irq_enter()
+ * and irq_exit() functions), 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_irq_enter(void)
+{
+	unsigned long flags;
+	struct rcu_dynticks *rdtp;
+	long long oldval;
+
+	local_irq_save(flags);
+	rdtp = &__get_cpu_var(rcu_dynticks);
+	oldval = rdtp->dynticks_nesting;
+	rdtp->dynticks_nesting++;
+	WARN_ON_ONCE(rdtp->dynticks_nesting == 0);
+	if (oldval)
+		trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting);
+	else
+		rcu_idle_exit_common(rdtp, oldval);
+	local_irq_restore(flags);
+}
+
+/**
+ * rcu_nmi_enter - inform RCU of entry to NMI context
+ *
+ * If the CPU was idle with dynamic ticks active, and there is no
+ * irq handler running, this updates rdtp->dynticks_nmi to let the
+ * RCU grace-period handling know that the CPU is active.
+ */
+void rcu_nmi_enter(void)
+{
+	struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
+
+	if (rdtp->dynticks_nmi_nesting == 0 &&
+	    (atomic_read(&rdtp->dynticks) & 0x1))
+		return;
+	rdtp->dynticks_nmi_nesting++;
+	smp_mb__before_atomic_inc();  /* Force delay from prior write. */
+	atomic_inc(&rdtp->dynticks);
+	/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
+	smp_mb__after_atomic_inc();  /* See above. */
+	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
+}
+
+/**
+ * rcu_nmi_exit - inform RCU of exit from NMI context
+ *
+ * If the CPU was idle with dynamic ticks active, and there is no
+ * irq handler running, this updates rdtp->dynticks_nmi to let the
+ * RCU grace-period handling know that the CPU is no longer active.
+ */
+void rcu_nmi_exit(void)
+{
+	struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
+
+	if (rdtp->dynticks_nmi_nesting == 0 ||
+	    --rdtp->dynticks_nmi_nesting != 0)
+		return;
+	/* 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 delay to next write. */
+	WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
+}
+
+#ifdef CONFIG_PROVE_RCU
+
+/**
+ * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
+ *
+ * If the current CPU is in its idle loop and is neither in an interrupt
+ * or NMI handler, return true.
+ */
+int rcu_is_cpu_idle(void)
+{
+	int ret;
+
+	preempt_disable();
+	ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0;
+	preempt_enable();
+	return ret;
+}
+EXPORT_SYMBOL(rcu_is_cpu_idle);
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Is the current CPU online?  Disable preemption to avoid false positives
+ * that could otherwise happen due to the current CPU number being sampled,
+ * this task being preempted, its old CPU being taken offline, resuming
+ * on some other CPU, then determining that its old CPU is now offline.
+ * It is OK to use RCU on an offline processor during initial boot, hence
+ * the check for rcu_scheduler_fully_active.  Note also that it is OK
+ * for a CPU coming online to use RCU for one jiffy prior to marking itself
+ * online in the cpu_online_mask.  Similarly, it is OK for a CPU going
+ * offline to continue to use RCU for one jiffy after marking itself
+ * offline in the cpu_online_mask.  This leniency is necessary given the
+ * non-atomic nature of the online and offline processing, for example,
+ * the fact that a CPU enters the scheduler after completing the CPU_DYING
+ * notifiers.
+ *
+ * This is also why RCU internally marks CPUs online during the
+ * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase.
+ *
+ * Disable checking if in an NMI handler because we cannot safely report
+ * errors from NMI handlers anyway.
+ */
+bool rcu_lockdep_current_cpu_online(void)
+{
+	struct rcu_data *rdp;
+	struct rcu_node *rnp;
+	bool ret;
+
+	if (in_nmi())
+		return 1;
+	preempt_disable();
+	rdp = &__get_cpu_var(rcu_sched_data);
+	rnp = rdp->mynode;
+	ret = (rdp->grpmask & rnp->qsmaskinit) ||
+	      !rcu_scheduler_fully_active;
+	preempt_enable();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
+/**
+ * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
+ *
+ * If the current CPU is idle or running at a first-level (not nested)
+ * interrupt from idle, return true.  The caller must have at least
+ * disabled preemption.
+ */
+int rcu_is_cpu_rrupt_from_idle(void)
+{
+	return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1;
+}
+
+/*
+ * Snapshot the specified CPU's dynticks counter so that we can later
+ * credit them with an implicit quiescent state.  Return 1 if this CPU
+ * is in dynticks idle mode, which is an extended quiescent state.
+ */
+static int dyntick_save_progress_counter(struct rcu_data *rdp)
+{
+	rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
+	return (rdp->dynticks_snap & 0x1) == 0;
+}
+
+/*
+ * Return true if the specified CPU has passed through a quiescent
+ * state by virtue of being in or having passed through an dynticks
+ * idle state since the last call to dyntick_save_progress_counter()
+ * for this same CPU.
+ */
+static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
+{
+	unsigned int curr;
+	unsigned int snap;
+
+	curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
+	snap = (unsigned int)rdp->dynticks_snap;
+
+	/*
+	 * If the CPU passed through or entered a dynticks idle phase with
+	 * no active irq/NMI handlers, then we can safely pretend that the CPU
+	 * already acknowledged the request to pass through a quiescent
+	 * state.  Either way, that CPU cannot possibly be in an RCU
+	 * read-side critical section that started before the beginning
+	 * of the current RCU grace period.
+	 */
+	if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
+		trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti");
+		rdp->dynticks_fqs++;
+		return 1;
+	}
+
+	/* Go check for the CPU being offline. */
+	return rcu_implicit_offline_qs(rdp);
+}
+
+static int jiffies_till_stall_check(void)
+{
+	int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
+
+	/*
+	 * Limit check must be consistent with the Kconfig limits
+	 * for CONFIG_RCU_CPU_STALL_TIMEOUT.
+	 */
+	if (till_stall_check < 3) {
+		ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
+		till_stall_check = 3;
+	} else if (till_stall_check > 300) {
+		ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
+		till_stall_check = 300;
+	}
+	return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
+}
+
+static void record_gp_stall_check_time(struct rcu_state *rsp)
+{
+	rsp->gp_start = jiffies;
+	rsp->jiffies_stall = jiffies + jiffies_till_stall_check();
+}
+
+static void print_other_cpu_stall(struct rcu_state *rsp)
+{
+	int cpu;
+	long delta;
+	unsigned long flags;
+	int ndetected;
+	struct rcu_node *rnp = rcu_get_root(rsp);
+
+	/* Only let one CPU complain about others per time interval. */
+
+	raw_spin_lock_irqsave(&rnp->lock, flags);
+	delta = jiffies - rsp->jiffies_stall;
+	if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+		return;
+	}
+	rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3;
+	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+
+	/*
+	 * OK, time to rat on our buddy...
+	 * 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:",
+	       rsp->name);
+	print_cpu_stall_info_begin();
+	rcu_for_each_leaf_node(rsp, rnp) {
+		raw_spin_lock_irqsave(&rnp->lock, flags);
+		ndetected += rcu_print_task_stall(rnp);
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+		if (rnp->qsmask == 0)
+			continue;
+		for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
+			if (rnp->qsmask & (1UL << cpu)) {
+				print_cpu_stall_info(rsp, rnp->grplo + cpu);
+				ndetected++;
+			}
+	}
+
+	/*
+	 * Now rat on any tasks that got kicked up to the root rcu_node
+	 * due to CPU offlining.
+	 */
+	rnp = rcu_get_root(rsp);
+	raw_spin_lock_irqsave(&rnp->lock, flags);
+	ndetected = rcu_print_task_stall(rnp);
+	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+
+	print_cpu_stall_info_end();
+	printk(KERN_CONT "(detected by %d, t=%ld jiffies)\n",
+	       smp_processor_id(), (long)(jiffies - rsp->gp_start));
+	if (ndetected == 0)
+		printk(KERN_ERR "INFO: Stall ended before state dump start\n");
+	else if (!trigger_all_cpu_backtrace())
+		dump_stack();
+
+	/* If so configured, complain about tasks blocking the grace period. */
+
+	rcu_print_detail_task_stall(rsp);
+
+	force_quiescent_state(rsp, 0);  /* Kick them all. */
+}
+
+static void print_cpu_stall(struct rcu_state *rsp)
+{
+	unsigned long flags;
+	struct rcu_node *rnp = rcu_get_root(rsp);
+
+	/*
+	 * OK, time to rat on ourselves...
+	 * 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);
+	print_cpu_stall_info_begin();
+	print_cpu_stall_info(rsp, smp_processor_id());
+	print_cpu_stall_info_end();
+	printk(KERN_CONT " (t=%lu jiffies)\n", jiffies - rsp->gp_start);
+	if (!trigger_all_cpu_backtrace())
+		dump_stack();
+
+	raw_spin_lock_irqsave(&rnp->lock, flags);
+	if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
+		rsp->jiffies_stall = jiffies +
+				     3 * jiffies_till_stall_check() + 3;
+	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+
+	set_need_resched();  /* kick ourselves to get things going. */
+}
+
+static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+	unsigned long j;
+	unsigned long js;
+	struct rcu_node *rnp;
+
+	if (rcu_cpu_stall_suppress)
+		return;
+	j = ACCESS_ONCE(jiffies);
+	js = ACCESS_ONCE(rsp->jiffies_stall);
+	rnp = rdp->mynode;
+	if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
+
+		/* We haven't checked in, so go dump stack. */
+		print_cpu_stall(rsp);
+
+	} else if (rcu_gp_in_progress(rsp) &&
+		   ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
+
+		/* They had a few time units to dump stack, so complain. */
+		print_other_cpu_stall(rsp);
+	}
+}
+
+static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
+{
+	rcu_cpu_stall_suppress = 1;
+	return NOTIFY_DONE;
+}
+
+/**
+ * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
+ *
+ * Set the stall-warning timeout way off into the future, thus preventing
+ * any RCU CPU stall-warning messages from appearing in the current set of
+ * RCU grace periods.
+ *
+ * The caller must disable hard irqs.
+ */
+void rcu_cpu_stall_reset(void)
+{
+	rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
+	rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
+	rcu_preempt_stall_reset();
+}
+
+static struct notifier_block rcu_panic_block = {
+	.notifier_call = rcu_panic,
+};
+
+static void __init check_cpu_stall_init(void)
+{
+	atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
+}
+
+/*
+ * 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");
+		if (rnp->qsmask & rdp->grpmask) {
+			rdp->qs_pending = 1;
+			rdp->passed_quiesce = 0;
+		} else
+			rdp->qs_pending = 0;
+		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;
+}
+
+/*
+ * 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.
+ */
+static void
+__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
+{
+	/* Did another grace period end? */
+	if (rdp->completed != rnp->completed) {
+
+		/* Advance callbacks.  No harm if list empty. */
+		rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
+		rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
+		rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+
+		/* Remember that we saw this grace-period completion. */
+		rdp->completed = rnp->completed;
+		trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend");
+
+		/*
+		 * 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.
+		 */
+		if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
+			rdp->gpnum = rdp->completed;
+
+		/*
+		 * If RCU does not need a quiescent state from this CPU,
+		 * then make sure that this CPU doesn't go looking for one.
+		 */
+		if ((rnp->qsmask & rdp->grpmask) == 0)
+			rdp->qs_pending = 0;
+	}
+}
+
+/*
+ * 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)
+{
+	unsigned long flags;
+	struct rcu_node *rnp;
+
+	local_irq_save(flags);
+	rnp = rdp->mynode;
+	if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */
+	    !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
+		local_irq_restore(flags);
+		return;
+	}
+	__rcu_process_gp_end(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);
+
+	/*
+	 * Because this CPU just now started the new grace period, we know
+	 * that all of its callbacks will be covered by this upcoming grace
+	 * period, even the ones that were registered arbitrarily recently.
+	 * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
+	 *
+	 * Other CPUs cannot be sure exactly when the grace period started.
+	 * Therefore, their recently registered callbacks must pass through
+	 * an additional RCU_NEXT_READY stage, so that they will be handled
+	 * by the next RCU grace period.
+	 */
+	rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+	rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+
+	/* Set state so that this CPU will detect the next quiescent state. */
+	__note_new_gpnum(rsp, rnp, rdp);
+}
+
+/*
+ * Start a new RCU grace period if warranted, re-initializing the hierarchy
+ * in preparation for detecting the next grace period.  The caller must hold
+ * the root node's ->lock, which is released before return.  Hard irqs must
+ * be disabled.
+ *
+ * Note that it is legal for a dying CPU (which is marked as offline) to
+ * invoke this function.  This can happen when the dying CPU reports its
+ * quiescent state.
+ */
+static void
+rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
+	__releases(rcu_get_root(rsp)->lock)
+{
+	struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
+	struct rcu_node *rnp = rcu_get_root(rsp);
+
+	if (!rcu_scheduler_fully_active ||
+	    !cpu_needs_another_gp(rsp, rdp)) {
+		/*
+		 * Either the scheduler hasn't yet spawned the first
+		 * non-idle task or this CPU does not need another
+		 * grace period.  Either way, don't start a new grace
+		 * period.
+		 */
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+		return;
+	}
+
+	if (rsp->fqs_active) {
+		/*
+		 * This CPU needs a grace period, but force_quiescent_state()
+		 * is running.  Tell it to start one on this CPU's behalf.
+		 */
+		rsp->fqs_need_gp = 1;
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+		return;
+	}
+
+	/* Advance to a new grace period and initialize state. */
+	rsp->gpnum++;
+	trace_rcu_grace_period(rsp->name, rsp->gpnum, "start");
+	WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT);
+	rsp->fqs_state = RCU_GP_INIT; /* Hold off force_quiescent_state. */
+	rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
+	record_gp_stall_check_time(rsp);
+	raw_spin_unlock(&rnp->lock);  /* leave irqs disabled. */
+
+	/* Exclude any concurrent CPU-hotplug operations. */
+	raw_spin_lock(&rsp->onofflock);  /* irqs already disabled. */
+
+	/*
+	 * Set the quiescent-state-needed bits in all the rcu_node
+	 * structures for all currently online CPUs in breadth-first
+	 * order, starting from the root rcu_node structure.  This
+	 * operation relies on the layout of the hierarchy within the
+	 * rsp->node[] array.  Note that other CPUs will access only
+	 * the leaves of the hierarchy, which still indicate that no
+	 * grace period is in progress, at least until the corresponding
+	 * leaf node has been initialized.  In addition, we have excluded
+	 * CPU-hotplug operations.
+	 *
+	 * Note that the grace period cannot complete until we finish
+	 * the initialization process, as there will be at least one
+	 * qsmask bit set in the root node until that time, namely the
+	 * one corresponding to this CPU, due to the fact that we have
+	 * irqs disabled.
+	 */
+	rcu_for_each_node_breadth_first(rsp, rnp) {
+		raw_spin_lock(&rnp->lock);	/* irqs already disabled. */
+		rcu_preempt_check_blocked_tasks(rnp);
+		rnp->qsmask = rnp->qsmaskinit;
+		rnp->gpnum = rsp->gpnum;
+		rnp->completed = rsp->completed;
+		if (rnp == rdp->mynode)
+			rcu_start_gp_per_cpu(rsp, rnp, rdp);
+		rcu_preempt_boost_start_gp(rnp);
+		trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
+					    rnp->level, rnp->grplo,
+					    rnp->grphi, rnp->qsmask);
+		raw_spin_unlock(&rnp->lock);	/* irqs remain disabled. */
+	}
+
+	rnp = rcu_get_root(rsp);
+	raw_spin_lock(&rnp->lock);		/* irqs already disabled. */
+	rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
+	raw_spin_unlock(&rnp->lock);		/* irqs remain disabled. */
+	raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
+}
+
+/*
+ * Report a full set of quiescent states to the specified rcu_state
+ * data structure.  This involves cleaning up after the prior grace
+ * period and letting rcu_start_gp() start up the next grace period
+ * if one is needed.  Note that the caller must hold rnp->lock, as
+ * required by rcu_start_gp(), which will release it.
+ */
+static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
+	__releases(rcu_get_root(rsp)->lock)
+{
+	unsigned long gp_duration;
+	struct rcu_node *rnp = rcu_get_root(rsp);
+	struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
+
+	WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
+
+	/*
+	 * Ensure that all grace-period and pre-grace-period activity
+	 * is seen before the assignment to rsp->completed.
+	 */
+	smp_mb(); /* See above block comment. */
+	gp_duration = jiffies - rsp->gp_start;
+	if (gp_duration > rsp->gp_max)
+		rsp->gp_max = gp_duration;
+
+	/*
+	 * We know the grace period is complete, but to everyone else
+	 * it appears to still be ongoing.  But it is also the case
+	 * that to everyone else it looks like there is nothing that
+	 * they can do to advance the grace period.  It is therefore
+	 * safe for us to drop the lock in order to mark the grace
+	 * period as completed in all of the rcu_node structures.
+	 *
+	 * But if this CPU needs another grace period, it will take
+	 * care of this while initializing the next grace period.
+	 * We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL
+	 * because the callbacks have not yet been advanced: Those
+	 * callbacks are waiting on the grace period that just now
+	 * completed.
+	 */
+	if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) {
+		raw_spin_unlock(&rnp->lock);	 /* irqs remain disabled. */
+
+		/*
+		 * Propagate new ->completed value to rcu_node structures
+		 * so that other CPUs don't have to wait until the start
+		 * of the next grace period to process their callbacks.
+		 */
+		rcu_for_each_node_breadth_first(rsp, rnp) {
+			raw_spin_lock(&rnp->lock); /* irqs already disabled. */
+			rnp->completed = rsp->gpnum;
+			raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+		}
+		rnp = rcu_get_root(rsp);
+		raw_spin_lock(&rnp->lock); /* irqs already disabled. */
+	}
+
+	rsp->completed = rsp->gpnum;  /* Declare the grace period complete. */
+	trace_rcu_grace_period(rsp->name, rsp->completed, "end");
+	rsp->fqs_state = RCU_GP_IDLE;
+	rcu_start_gp(rsp, flags);  /* releases root node's rnp->lock. */
+}
+
+/*
+ * Similar to rcu_report_qs_rdp(), for which it is a helper function.
+ * Allows quiescent states for a group of CPUs to be reported at one go
+ * to the specified rcu_node structure, though all the CPUs in the group
+ * must be represented by the same rcu_node structure (which need not be
+ * a leaf rcu_node structure, though it often will be).  That structure's
+ * lock must be held upon entry, and it is released before return.
+ */
+static void
+rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
+		  struct rcu_node *rnp, unsigned long flags)
+	__releases(rnp->lock)
+{
+	struct rcu_node *rnp_c;
+
+	/* Walk up the rcu_node hierarchy. */
+	for (;;) {
+		if (!(rnp->qsmask & mask)) {
+
+			/* Our bit has already been cleared, so done. */
+			raw_spin_unlock_irqrestore(&rnp->lock, flags);
+			return;
+		}
+		rnp->qsmask &= ~mask;
+		trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
+						 mask, rnp->qsmask, rnp->level,
+						 rnp->grplo, rnp->grphi,
+						 !!rnp->gp_tasks);
+		if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
+
+			/* Other bits still set at this level, so done. */
+			raw_spin_unlock_irqrestore(&rnp->lock, flags);
+			return;
+		}
+		mask = rnp->grpmask;
+		if (rnp->parent == NULL) {
+
+			/* No more levels.  Exit loop holding root lock. */
+
+			break;
+		}
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+		rnp_c = rnp;
+		rnp = rnp->parent;
+		raw_spin_lock_irqsave(&rnp->lock, flags);
+		WARN_ON_ONCE(rnp_c->qsmask);
+	}
+
+	/*
+	 * Get here if we are the last CPU to pass through a quiescent
+	 * state for this grace period.  Invoke rcu_report_qs_rsp()
+	 * to clean up and start the next grace period if one is needed.
+	 */
+	rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
+}
+
+/*
+ * Record a quiescent state for the specified CPU to that CPU's rcu_data
+ * structure.  This must be either called from the specified CPU, or
+ * called when the specified CPU is known to be offline (and when it is
+ * also known that no other CPU is concurrently trying to help the offline
+ * CPU).  The lastcomp argument is used to make sure we are still in the
+ * grace period of interest.  We don't want to end the current grace period
+ * based on quiescent states detected in an earlier grace period!
+ */
+static void
+rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp)
+{
+	unsigned long flags;
+	unsigned long mask;
+	struct rcu_node *rnp;
+
+	rnp = rdp->mynode;
+	raw_spin_lock_irqsave(&rnp->lock, flags);
+	if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) {
+
+		/*
+		 * The grace period in which this quiescent state was
+		 * recorded has ended, so don't report it upwards.
+		 * We will instead need a new quiescent state that lies
+		 * within the current grace period.
+		 */
+		rdp->passed_quiesce = 0;	/* need qs for new gp. */
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+		return;
+	}
+	mask = rdp->grpmask;
+	if ((rnp->qsmask & mask) == 0) {
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	} else {
+		rdp->qs_pending = 0;
+
+		/*
+		 * This GP can't end until cpu checks in, so all of our
+		 * callbacks can be processed during the next GP.
+		 */
+		rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+
+		rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
+	}
+}
+
+/*
+ * Check to see if there is a new grace period of which this CPU
+ * is not yet aware, and if so, set up local rcu_data state for it.
+ * Otherwise, see if this CPU has just passed through its first
+ * quiescent state for this grace period, and record that fact if so.
+ */
+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;
+
+	/*
+	 * Does this CPU still need to do its part for current grace period?
+	 * If no, return and let the other CPUs do their part as well.
+	 */
+	if (!rdp->qs_pending)
+		return;
+
+	/*
+	 * Was there a quiescent state since the beginning of the grace
+	 * period? If no, then exit and wait for the next call.
+	 */
+	if (!rdp->passed_quiesce)
+		return;
+
+	/*
+	 * Tell RCU we are done (but rcu_report_qs_rdp() will be the
+	 * judge of that).
+	 */
+	rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Move a dying CPU's RCU callbacks to online CPU's callback list.
+ * Also record a quiescent state for this CPU for the current grace period.
+ * Synchronization and interrupt disabling are not required because
+ * this function executes in stop_machine() context.  Therefore, cleanup
+ * operations that might block must be done later from the CPU_DEAD
+ * notifier.
+ *
+ * Note that the outgoing CPU's bit has already been cleared in the
+ * cpu_online_mask.  This allows us to randomly pick a callback
+ * destination from the bits set in that mask.
+ */
+static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
+{
+	int i;
+	unsigned long mask;
+	int receive_cpu = cpumask_any(cpu_online_mask);
+	struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
+	struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu);
+	RCU_TRACE(struct rcu_node *rnp = rdp->mynode); /* For dying CPU. */
+
+	/* First, adjust the counts. */
+	if (rdp->nxtlist != NULL) {
+		receive_rdp->qlen_lazy += rdp->qlen_lazy;
+		receive_rdp->qlen += rdp->qlen;
+		rdp->qlen_lazy = 0;
+		rdp->qlen = 0;
+	}
+
+	/*
+	 * Next, move ready-to-invoke callbacks to be invoked on some
+	 * other CPU.  These will not be required to pass through another
+	 * grace period:  They are done, regardless of CPU.
+	 */
+	if (rdp->nxtlist != NULL &&
+	    rdp->nxttail[RCU_DONE_TAIL] != &rdp->nxtlist) {
+		struct rcu_head *oldhead;
+		struct rcu_head **oldtail;
+		struct rcu_head **newtail;
+
+		oldhead = rdp->nxtlist;
+		oldtail = receive_rdp->nxttail[RCU_DONE_TAIL];
+		rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
+		*rdp->nxttail[RCU_DONE_TAIL] = *oldtail;
+		*receive_rdp->nxttail[RCU_DONE_TAIL] = oldhead;
+		newtail = rdp->nxttail[RCU_DONE_TAIL];
+		for (i = RCU_DONE_TAIL; i < RCU_NEXT_SIZE; i++) {
+			if (receive_rdp->nxttail[i] == oldtail)
+				receive_rdp->nxttail[i] = newtail;
+			if (rdp->nxttail[i] == newtail)
+				rdp->nxttail[i] = &rdp->nxtlist;
+		}
+	}
+
+	/*
+	 * Finally, put the rest of the callbacks at the end of the list.
+	 * The ones that made it partway through get to start over:  We
+	 * cannot assume that grace periods are synchronized across CPUs.
+	 * (We could splice RCU_WAIT_TAIL into RCU_NEXT_READY_TAIL, but
+	 * this does not seem compelling.  Not yet, anyway.)
+	 */
+	if (rdp->nxtlist != NULL) {
+		*receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
+		receive_rdp->nxttail[RCU_NEXT_TAIL] =
+				rdp->nxttail[RCU_NEXT_TAIL];
+		receive_rdp->n_cbs_adopted += rdp->qlen;
+		rdp->n_cbs_orphaned += rdp->qlen;
+
+		rdp->nxtlist = NULL;
+		for (i = 0; i < RCU_NEXT_SIZE; i++)
+			rdp->nxttail[i] = &rdp->nxtlist;
+	}
+
+	/*
+	 * Record a quiescent state for the dying CPU.  This is safe
+	 * only because we have already cleared out the callbacks.
+	 * (Otherwise, the RCU core might try to schedule the invocation
+	 * of callbacks on this now-offline CPU, which would be bad.)
+	 */
+	mask = rdp->grpmask;	/* rnp->grplo is constant. */
+	trace_rcu_grace_period(rsp->name,
+			       rnp->gpnum + 1 - !!(rnp->qsmask & mask),
+			       "cpuofl");
+	rcu_report_qs_rdp(smp_processor_id(), rsp, rdp, rsp->gpnum);
+	/* Note that rcu_report_qs_rdp() might call trace_rcu_grace_period(). */
+}
+
+/*
+ * The CPU has been completely removed, and some other CPU is reporting
+ * this fact from process context.  Do the remainder of the cleanup.
+ * There can only be one CPU hotplug operation at a time, so no other
+ * CPU can be attempting to update rcu_cpu_kthread_task.
+ */
+static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
+{
+	unsigned long flags;
+	unsigned long mask;
+	int need_report = 0;
+	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+	struct rcu_node *rnp = rdp->mynode;  /* Outgoing CPU's rnp. */
+
+	/* Adjust any no-longer-needed kthreads. */
+	rcu_stop_cpu_kthread(cpu);
+	rcu_node_kthread_setaffinity(rnp, -1);
+
+	/* Remove the dying CPU from the bitmasks in the rcu_node hierarchy. */
+
+	/* Exclude any attempts to start a new grace period. */
+	raw_spin_lock_irqsave(&rsp->onofflock, flags);
+
+	/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
+	mask = rdp->grpmask;	/* rnp->grplo is constant. */
+	do {
+		raw_spin_lock(&rnp->lock);	/* irqs already disabled. */
+		rnp->qsmaskinit &= ~mask;
+		if (rnp->qsmaskinit != 0) {
+			if (rnp != rdp->mynode)
+				raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+			break;
+		}
+		if (rnp == rdp->mynode)
+			need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
+		else
+			raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+		mask = rnp->grpmask;
+		rnp = rnp->parent;
+	} while (rnp != NULL);
+
+	/*
+	 * We still hold the leaf rcu_node structure lock here, and
+	 * irqs are still disabled.  The reason for this subterfuge is
+	 * because invoking rcu_report_unblock_qs_rnp() with ->onofflock
+	 * held leads to deadlock.
+	 */
+	raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
+	rnp = rdp->mynode;
+	if (need_report & RCU_OFL_TASKS_NORM_GP)
+		rcu_report_unblock_qs_rnp(rnp, flags);
+	else
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	if (need_report & RCU_OFL_TASKS_EXP_GP)
+		rcu_report_exp_rnp(rsp, rnp, true);
+}
+
+#else /* #ifdef CONFIG_HOTPLUG_CPU */
+
+static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
+{
+}
+
+static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
+{
+}
+
+#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
+
+/*
+ * Invoke any RCU callbacks that have made it to the end of their grace
+ * period.  Thottle as specified by rdp->blimit.
+ */
+static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+	unsigned long flags;
+	struct rcu_head *next, *list, **tail;
+	long bl, count, count_lazy;
+
+	/* If no callbacks are ready, just return.*/
+	if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
+		trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0);
+		trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist),
+				    need_resched(), is_idle_task(current),
+				    rcu_is_callbacks_kthread());
+		return;
+	}
+
+	/*
+	 * Extract the list of ready callbacks, disabling to prevent
+	 * races with call_rcu() from interrupt handlers.
+	 */
+	local_irq_save(flags);
+	WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
+	bl = rdp->blimit;
+	trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
+	list = rdp->nxtlist;
+	rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
+	*rdp->nxttail[RCU_DONE_TAIL] = NULL;
+	tail = rdp->nxttail[RCU_DONE_TAIL];
+	for (count = RCU_NEXT_SIZE - 1; count >= 0; count--)
+		if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL])
+			rdp->nxttail[count] = &rdp->nxtlist;
+	local_irq_restore(flags);
+
+	/* Invoke callbacks. */
+	count = count_lazy = 0;
+	while (list) {
+		next = list->next;
+		prefetch(next);
+		debug_rcu_head_unqueue(list);
+		if (__rcu_reclaim(rsp->name, list))
+			count_lazy++;
+		list = next;
+		/* Stop only if limit reached and CPU has something to do. */
+		if (++count >= bl &&
+		    (need_resched() ||
+		     (!is_idle_task(current) && !rcu_is_callbacks_kthread())))
+			break;
+	}
+
+	local_irq_save(flags);
+	trace_rcu_batch_end(rsp->name, count, !!list, need_resched(),
+			    is_idle_task(current),
+			    rcu_is_callbacks_kthread());
+
+	/* Update count, and requeue any remaining callbacks. */
+	rdp->qlen_lazy -= count_lazy;
+	rdp->qlen -= count;
+	rdp->n_cbs_invoked += count;
+	if (list != NULL) {
+		*tail = rdp->nxtlist;
+		rdp->nxtlist = list;
+		for (count = 0; count < RCU_NEXT_SIZE; count++)
+			if (&rdp->nxtlist == rdp->nxttail[count])
+				rdp->nxttail[count] = tail;
+			else
+				break;
+	}
+
+	/* Reinstate batch limit if we have worked down the excess. */
+	if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
+		rdp->blimit = blimit;
+
+	/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
+	if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
+		rdp->qlen_last_fqs_check = 0;
+		rdp->n_force_qs_snap = rsp->n_force_qs;
+	} else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
+		rdp->qlen_last_fqs_check = rdp->qlen;
+
+	local_irq_restore(flags);
+
+	/* Re-invoke RCU core processing if there are callbacks remaining. */
+	if (cpu_has_callbacks_ready_to_invoke(rdp))
+		invoke_rcu_core();
+}
+
+/*
+ * Check to see if this CPU is in a non-context-switch quiescent state
+ * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
+ * Also schedule RCU core processing.
+ *
+ * This function must be called from hardirq context.  It is normally
+ * invoked from the scheduling-clock interrupt.  If rcu_pending returns
+ * false, there is no point in invoking rcu_check_callbacks().
+ */
+void rcu_check_callbacks(int cpu, int user)
+{
+	trace_rcu_utilization("Start scheduler-tick");
+	increment_cpu_stall_ticks();
+	if (user || rcu_is_cpu_rrupt_from_idle()) {
+
+		/*
+		 * Get here if this CPU took its interrupt from user
+		 * mode or from the idle loop, and if this is not a
+		 * nested interrupt.  In this case, the CPU is in
+		 * a quiescent state, so note it.
+		 *
+		 * No memory barrier is required here because both
+		 * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
+		 * variables that other CPUs neither access nor modify,
+		 * at least not while the corresponding CPU is online.
+		 */
+
+		rcu_sched_qs(cpu);
+		rcu_bh_qs(cpu);
+
+	} else if (!in_softirq()) {
+
+		/*
+		 * Get here if this CPU did not take its interrupt from
+		 * softirq, in other words, if it is not interrupting
+		 * a rcu_bh read-side critical section.  This is an _bh
+		 * critical section, so note it.
+		 */
+
+		rcu_bh_qs(cpu);
+	}
+	rcu_preempt_check_callbacks(cpu);
+	if (rcu_pending(cpu))
+		invoke_rcu_core();
+	trace_rcu_utilization("End scheduler-tick");
+}
+
+/*
+ * Scan the leaf rcu_node structures, processing dyntick state for any that
+ * have not yet encountered a quiescent state, using the function specified.
+ * Also initiate boosting for any threads blocked on the root rcu_node.
+ *
+ * The caller must have suppressed start of new grace periods.
+ */
+static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
+{
+	unsigned long bit;
+	int cpu;
+	unsigned long flags;
+	unsigned long mask;
+	struct rcu_node *rnp;
+
+	rcu_for_each_leaf_node(rsp, rnp) {
+		mask = 0;
+		raw_spin_lock_irqsave(&rnp->lock, flags);
+		if (!rcu_gp_in_progress(rsp)) {
+			raw_spin_unlock_irqrestore(&rnp->lock, flags);
+			return;
+		}
+		if (rnp->qsmask == 0) {
+			rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
+			continue;
+		}
+		cpu = rnp->grplo;
+		bit = 1;
+		for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
+			if ((rnp->qsmask & bit) != 0 &&
+			    f(per_cpu_ptr(rsp->rda, cpu)))
+				mask |= bit;
+		}
+		if (mask != 0) {
+
+			/* rcu_report_qs_rnp() releases rnp->lock. */
+			rcu_report_qs_rnp(mask, rsp, rnp, flags);
+			continue;
+		}
+		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+	}
+	rnp = rcu_get_root(rsp);
+	if (rnp->qsmask == 0) {
+		raw_spin_lock_irqsave(&rnp->lock, flags);
+		rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
+	}
+}
+
+/*
+ * Force quiescent states on reluctant CPUs, and also detect which
+ * CPUs are in dyntick-idle mode.
+ */
+static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
+{
+	unsigned long flags;
+	struct rcu_node *rnp = rcu_get_root(rsp);
+
+	trace_rcu_utilization("Start fqs");
+	if (!rcu_gp_in_progress(rsp)) {
+		trace_rcu_utilization("End fqs");
+		return;  /* No grace period in progress, nothing to force. */
+	}
+	if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) {
+		rsp->n_force_qs_lh++; /* Inexact, can lose counts.  Tough! */
+		trace_rcu_utilization("End fqs");
+		return;	/* Someone else is already on the job. */
+	}
+	if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
+		goto unlock_fqs_ret; /* no emergency and done recently. */
+	rsp->n_force_qs++;
+	raw_spin_lock(&rnp->lock);  /* irqs already disabled */
+	rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
+	if(!rcu_gp_in_progress(rsp)) {
+		rsp->n_force_qs_ngp++;
+		raw_spin_unlock(&rnp->lock);  /* irqs remain disabled */
+		goto unlock_fqs_ret;  /* no GP in progress, time updated. */
+	}
+	rsp->fqs_active = 1;
+	switch (rsp->fqs_state) {
+	case RCU_GP_IDLE:
+	case RCU_GP_INIT:
+
+		break; /* grace period idle or initializing, ignore. */
+
+	case RCU_SAVE_DYNTICK:
+		if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
+			break; /* So gcc recognizes the dead code. */
+
+		raw_spin_unlock(&rnp->lock);  /* irqs remain disabled */
+
+		/* Record dyntick-idle state. */
+		force_qs_rnp(rsp, dyntick_save_progress_counter);
+		raw_spin_lock(&rnp->lock);  /* irqs already disabled */
+		if (rcu_gp_in_progress(rsp))
+			rsp->fqs_state = RCU_FORCE_QS;
+		break;
+
+	case RCU_FORCE_QS:
+
+		/* Check dyntick-idle state, send IPI to laggarts. */
+		raw_spin_unlock(&rnp->lock);  /* irqs remain disabled */
+		force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
+
+		/* Leave state in case more forcing is required. */
+
+		raw_spin_lock(&rnp->lock);  /* irqs already disabled */
+		break;
+	}
+	rsp->fqs_active = 0;
+	if (rsp->fqs_need_gp) {
+		raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */
+		rsp->fqs_need_gp = 0;
+		rcu_start_gp(rsp, flags); /* releases rnp->lock */
+		trace_rcu_utilization("End fqs");
+		return;
+	}
+	raw_spin_unlock(&rnp->lock);  /* irqs remain disabled */
+unlock_fqs_ret:
+	raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
+	trace_rcu_utilization("End fqs");
+}
+
+/*
+ * This does the RCU core processing work for the specified rcu_state
+ * and rcu_data structures.  This may be called only from the CPU to
+ * whom the rdp belongs.
+ */
+static void
+__rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+	unsigned long flags;
+
+	WARN_ON_ONCE(rdp->beenonline == 0);
+
+	/*
+	 * If an RCU GP has gone long enough, go check for dyntick
+	 * idle CPUs and, if needed, send resched IPIs.
+	 */
+	if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
+		force_quiescent_state(rsp, 1);
+
+	/*
+	 * Advance callbacks in response to end of earlier 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);
+
+	/* Does this CPU require a not-yet-started grace period? */
+	if (cpu_needs_another_gp(rsp, rdp)) {
+		raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
+		rcu_start_gp(rsp, flags);  /* releases above lock */
+	}
+
+	/* If there are callbacks ready, invoke them. */
+	if (cpu_has_callbacks_ready_to_invoke(rdp))
+		invoke_rcu_callbacks(rsp, rdp);
+}
+
+/*
+ * Do RCU core processing for the current CPU.
+ */
+static void rcu_process_callbacks(struct softirq_action *unused)
+{
+	trace_rcu_utilization("Start RCU core");
+	__rcu_process_callbacks(&rcu_sched_state,
+				&__get_cpu_var(rcu_sched_data));
+	__rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
+	rcu_preempt_process_callbacks();
+	trace_rcu_utilization("End RCU core");
+}
+
+/*
+ * Schedule RCU callback invocation.  If the specified type of RCU
+ * does not support RCU priority boosting, just do a direct call,
+ * otherwise wake up the per-CPU kernel kthread.  Note that because we
+ * are running on the current CPU with interrupts disabled, the
+ * rcu_cpu_kthread_task cannot disappear out from under us.
+ */
+static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+	if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
+		return;
+	if (likely(!rsp->boost)) {
+		rcu_do_batch(rsp, rdp);
+		return;
+	}
+	invoke_rcu_callbacks_kthread();
+}
+
+static void invoke_rcu_core(void)
+{
+	raise_softirq(RCU_SOFTIRQ);
+}
+
+static void
+__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
+	   struct rcu_state *rsp, bool lazy)
+{
+	unsigned long flags;
+	struct rcu_data *rdp;
+
+	WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
+	debug_rcu_head_queue(head);
+	head->func = func;
+	head->next = NULL;
+
+	smp_mb(); /* Ensure RCU update seen before callback registry. */
+
+	/*
+	 * Opportunistically note grace-period endings and beginnings.
+	 * Note that we might see a beginning right after we see an
+	 * end, but never vice versa, since this CPU has to pass through
+	 * a quiescent state betweentimes.
+	 */
+	local_irq_save(flags);
+	rdp = this_cpu_ptr(rsp->rda);
+
+	/* Add the callback to our list. */
+	*rdp->nxttail[RCU_NEXT_TAIL] = head;
+	rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
+	rdp->qlen++;
+	if (lazy)
+		rdp->qlen_lazy++;
+
+	if (__is_kfree_rcu_offset((unsigned long)func))
+		trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
+					 rdp->qlen_lazy, rdp->qlen);
+	else
+		trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
+
+	/* If interrupts were disabled, don't dive into RCU core. */
+	if (irqs_disabled_flags(flags)) {
+		local_irq_restore(flags);
+		return;
+	}
+
+	/*
+	 * Force the grace period if too many callbacks or too long waiting.
+	 * Enforce hysteresis, and don't invoke force_quiescent_state()
+	 * if some other CPU has recently done so.  Also, don't bother
+	 * invoking force_quiescent_state() if the newly enqueued callback
+	 * is the only one waiting for a grace period to complete.
+	 */
+	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);
+
+		/* Start a new grace period if one not already started. */
+		if (!rcu_gp_in_progress(rsp)) {
+			unsigned long nestflag;
+			struct rcu_node *rnp_root = rcu_get_root(rsp);
+
+			raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
+			rcu_start_gp(rsp, nestflag);  /* rlses rnp_root->lock */
+		} else {
+			/* Give the grace period a kick. */
+			rdp->blimit = LONG_MAX;
+			if (rsp->n_force_qs == rdp->n_force_qs_snap &&
+			    *rdp->nxttail[RCU_DONE_TAIL] != head)
+				force_quiescent_state(rsp, 0);
+			rdp->n_force_qs_snap = rsp->n_force_qs;
+			rdp->qlen_last_fqs_check = rdp->qlen;
+		}
+	} else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
+		force_quiescent_state(rsp, 1);
+	local_irq_restore(flags);
+}
+
+/*
+ * Queue an RCU-sched callback for invocation after a grace period.
+ */
+void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, &rcu_sched_state, 0);
+}
+EXPORT_SYMBOL_GPL(call_rcu_sched);
+
+#ifndef CONFIG_PREEMPT_RT_FULL
+/*
+ * Queue an RCU callback for invocation after a quicker grace period.
+ */
+void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, &rcu_bh_state, 0);
+}
+EXPORT_SYMBOL_GPL(call_rcu_bh);
+#endif
+
+/**
+ * synchronize_sched - wait until an rcu-sched grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu-sched
+ * grace period has elapsed, in other words after all currently executing
+ * rcu-sched read-side critical sections have completed.   These read-side
+ * critical sections are delimited by rcu_read_lock_sched() and
+ * rcu_read_unlock_sched(), and may be nested.  Note that preempt_disable(),
+ * local_irq_disable(), and so on may be used in place of
+ * rcu_read_lock_sched().
+ *
+ * This means that all preempt_disable code sequences, including NMI and
+ * hardware-interrupt handlers, in progress on entry will have completed
+ * before this primitive returns.  However, this does not guarantee that
+ * softirq handlers will have completed, since in some kernels, these
+ * handlers can run in process context, and can block.
+ *
+ * This primitive provides the guarantees made by the (now removed)
+ * synchronize_kernel() API.  In contrast, synchronize_rcu() only
+ * guarantees that rcu_read_lock() sections will have completed.
+ * In "classic RCU", these two guarantees happen to be one and
+ * the same, but can differ in realtime RCU implementations.
+ */
+void synchronize_sched(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_sched() in RCU-sched read-side critical section");
+	if (rcu_blocking_is_gp())
+		return;
+	wait_rcu_gp(call_rcu_sched);
+}
+EXPORT_SYMBOL_GPL(synchronize_sched);
+
+#ifndef CONFIG_PREEMPT_RT_FULL
+/**
+ * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu_bh grace
+ * period has elapsed, in other words after all currently executing rcu_bh
+ * read-side critical sections have completed.  RCU read-side critical
+ * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
+ * and may be nested.
+ */
+void synchronize_rcu_bh(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_bh() in RCU-bh read-side critical section");
+	if (rcu_blocking_is_gp())
+		return;
+	wait_rcu_gp(call_rcu_bh);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
+#endif
+
+static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0);
+static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0);
+
+static int synchronize_sched_expedited_cpu_stop(void *data)
+{
+	/*
+	 * There must be a full memory barrier on each affected CPU
+	 * between the time that try_stop_cpus() is called and the
+	 * time that it returns.
+	 *
+	 * In the current initial implementation of cpu_stop, the
+	 * above condition is already met when the control reaches
+	 * this point and the following smp_mb() is not strictly
+	 * necessary.  Do smp_mb() anyway for documentation and
+	 * robustness against future implementation changes.
+	 */
+	smp_mb(); /* See above comment block. */
+	return 0;
+}
+
+/**
+ * synchronize_sched_expedited - Brute-force RCU-sched grace period
+ *
+ * Wait for an RCU-sched grace period to elapse, but use a "big hammer"
+ * approach to force the grace period to end quickly.  This consumes
+ * significant time on all CPUs and is unfriendly to real-time workloads,
+ * so is thus not recommended for any sort of common-case code.  In fact,
+ * if you are using synchronize_sched_expedited() in a loop, please
+ * restructure your code to batch your updates, and then use a single
+ * synchronize_sched() instead.
+ *
+ * Note that it is illegal to call this function while holding any lock
+ * that is acquired by a CPU-hotplug notifier.  And yes, it is also illegal
+ * to call this function from a CPU-hotplug notifier.  Failing to observe
+ * these restriction will result in deadlock.
+ *
+ * This implementation can be thought of as an application of ticket
+ * locking to RCU, with sync_sched_expedited_started and
+ * sync_sched_expedited_done taking on the roles of the halves
+ * of the ticket-lock word.  Each task atomically increments
+ * sync_sched_expedited_started upon entry, snapshotting the old value,
+ * then attempts to stop all the CPUs.  If this succeeds, then each
+ * CPU will have executed a context switch, resulting in an RCU-sched
+ * grace period.  We are then done, so we use atomic_cmpxchg() to
+ * update sync_sched_expedited_done to match our snapshot -- but
+ * only if someone else has not already advanced past our snapshot.
+ *
+ * On the other hand, if try_stop_cpus() fails, we check the value
+ * of sync_sched_expedited_done.  If it has advanced past our
+ * initial snapshot, then someone else must have forced a grace period
+ * some time after we took our snapshot.  In this case, our work is
+ * done for us, and we can simply return.  Otherwise, we try again,
+ * but keep our initial snapshot for purposes of checking for someone
+ * doing our work for us.
+ *
+ * If we fail too many times in a row, we fall back to synchronize_sched().
+ */
+void synchronize_sched_expedited(void)
+{
+	int firstsnap, s, snap, trycount = 0;
+
+	/* Note that atomic_inc_return() implies full memory barrier. */
+	firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
+	get_online_cpus();
+	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
+
+	/*
+	 * Each pass through the following loop attempts to force a
+	 * context switch on each CPU.
+	 */
+	while (try_stop_cpus(cpu_online_mask,
+			     synchronize_sched_expedited_cpu_stop,
+			     NULL) == -EAGAIN) {
+		put_online_cpus();
+
+		/* No joy, try again later.  Or just synchronize_sched(). */
+		if (trycount++ < 10)
+			udelay(trycount * num_online_cpus());
+		else {
+			synchronize_sched();
+			return;
+		}
+
+		/* Check to see if someone else did our work for us. */
+		s = atomic_read(&sync_sched_expedited_done);
+		if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) {
+			smp_mb(); /* ensure test happens before caller kfree */
+			return;
+		}
+
+		/*
+		 * Refetching sync_sched_expedited_started allows later
+		 * callers to piggyback on our grace period.  We subtract
+		 * 1 to get the same token that the last incrementer got.
+		 * We retry after they started, so our grace period works
+		 * for them, and they started after our first try, so their
+		 * grace period works for us.
+		 */
+		get_online_cpus();
+		snap = atomic_read(&sync_sched_expedited_started);
+		smp_mb(); /* ensure read is before try_stop_cpus(). */
+	}
+
+	/*
+	 * Everyone up to our most recent fetch is covered by our grace
+	 * period.  Update the counter, but only if our work is still
+	 * relevant -- which it won't be if someone who started later
+	 * than we did beat us to the punch.
+	 */
+	do {
+		s = atomic_read(&sync_sched_expedited_done);
+		if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) {
+			smp_mb(); /* ensure test happens before caller kfree */
+			break;
+		}
+	} while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s);
+
+	put_online_cpus();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
+
+/*
+ * Check to see if there is any immediate RCU-related work to be done
+ * by the current CPU, for the specified type of RCU, returning 1 if so.
+ * The checks are in order of increasing expense: checks that can be
+ * carried out against CPU-local state are performed first.  However,
+ * we must check for CPU stalls first, else we might not get a chance.
+ */
+static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+	struct rcu_node *rnp = rdp->mynode;
+
+	rdp->n_rcu_pending++;
+
+	/* Check for CPU stalls, if enabled. */
+	check_cpu_stall(rsp, rdp);
+
+	/* Is the RCU core waiting for a quiescent state from this CPU? */
+	if (rcu_scheduler_fully_active &&
+	    rdp->qs_pending && !rdp->passed_quiesce) {
+
+		/*
+		 * If force_quiescent_state() coming soon and this CPU
+		 * needs a quiescent state, and this is either RCU-sched
+		 * or RCU-bh, force a local reschedule.
+		 */
+		rdp->n_rp_qs_pending++;
+		if (!rdp->preemptible &&
+		    ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
+				 jiffies))
+			set_need_resched();
+	} else if (rdp->qs_pending && rdp->passed_quiesce) {
+		rdp->n_rp_report_qs++;
+		return 1;
+	}
+
+	/* Does this CPU have callbacks ready to invoke? */
+	if (cpu_has_callbacks_ready_to_invoke(rdp)) {
+		rdp->n_rp_cb_ready++;
+		return 1;
+	}
+
+	/* Has RCU gone idle with this CPU needing another grace period? */
+	if (cpu_needs_another_gp(rsp, rdp)) {
+		rdp->n_rp_cpu_needs_gp++;
+		return 1;
+	}
+
+	/* Has another RCU grace period completed?  */
+	if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
+		rdp->n_rp_gp_completed++;
+		return 1;
+	}
+
+	/* Has a new RCU grace period started? */
+	if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
+		rdp->n_rp_gp_started++;
+		return 1;
+	}
+
+	/* Has an RCU GP gone long enough to send resched IPIs &c? */
+	if (rcu_gp_in_progress(rsp) &&
+	    ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) {
+		rdp->n_rp_need_fqs++;
+		return 1;
+	}
+
+	/* nothing to do */
+	rdp->n_rp_need_nothing++;
+	return 0;
+}
+
+/*
+ * Check to see if there is any immediate RCU-related work to be done
+ * by the current CPU, returning 1 if so.  This function is part of the
+ * RCU implementation; it is -not- an exported member of the RCU API.
+ */
+static int rcu_pending(int cpu)
+{
+	return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
+	       __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) ||
+	       rcu_preempt_pending(cpu);
+}
+
+/*
+ * Check to see if any future RCU-related work will need to be done
+ * by the current CPU, even if none need be done immediately, returning
+ * 1 if so.
+ */
+static int rcu_cpu_has_callbacks(int cpu)
+{
+	/* RCU callbacks either ready or pending? */
+	return per_cpu(rcu_sched_data, cpu).nxtlist ||
+	       per_cpu(rcu_bh_data, cpu).nxtlist ||
+	       rcu_preempt_cpu_has_callbacks(cpu);
+}
+
+static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
+static atomic_t rcu_barrier_cpu_count;
+static DEFINE_MUTEX(rcu_barrier_mutex);
+static struct completion rcu_barrier_completion;
+
+static void rcu_barrier_callback(struct rcu_head *notused)
+{
+	if (atomic_dec_and_test(&rcu_barrier_cpu_count))
+		complete(&rcu_barrier_completion);
+}
+
+/*
+ * Called with preemption disabled, and from cross-cpu IRQ context.
+ */
+static void rcu_barrier_func(void *type)
+{
+	int cpu = smp_processor_id();
+	struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
+	void (*call_rcu_func)(struct rcu_head *head,
+			      void (*func)(struct rcu_head *head));
+
+	atomic_inc(&rcu_barrier_cpu_count);
+	call_rcu_func = type;
+	call_rcu_func(head, rcu_barrier_callback);
+}
+
+/*
+ * Orchestrate the specified type of RCU barrier, waiting for all
+ * RCU callbacks of the specified type to complete.
+ */
+static void _rcu_barrier(struct rcu_state *rsp,
+			 void (*call_rcu_func)(struct rcu_head *head,
+					       void (*func)(struct rcu_head *head)))
+{
+	BUG_ON(in_interrupt());
+	/* Take mutex to serialize concurrent rcu_barrier() requests. */
+	mutex_lock(&rcu_barrier_mutex);
+	init_completion(&rcu_barrier_completion);
+	/*
+	 * Initialize rcu_barrier_cpu_count to 1, then invoke
+	 * rcu_barrier_func() on each CPU, so that each CPU also has
+	 * incremented rcu_barrier_cpu_count.  Only then is it safe to
+	 * decrement rcu_barrier_cpu_count -- otherwise the first CPU
+	 * might complete its grace period before all of the other CPUs
+	 * did their increment, causing this function to return too
+	 * early.  Note that on_each_cpu() disables irqs, which prevents
+	 * any CPUs from coming online or going offline until each online
+	 * CPU has queued its RCU-barrier callback.
+	 */
+	atomic_set(&rcu_barrier_cpu_count, 1);
+	on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
+	if (atomic_dec_and_test(&rcu_barrier_cpu_count))
+		complete(&rcu_barrier_completion);
+	wait_for_completion(&rcu_barrier_completion);
+	mutex_unlock(&rcu_barrier_mutex);
+}
+
+#ifndef CONFIG_PREEMPT_RT_FULL
+/**
+ * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
+ */
+void rcu_barrier_bh(void)
+{
+	_rcu_barrier(&rcu_bh_state, call_rcu_bh);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+#endif
+
+/**
+ * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
+ */
+void rcu_barrier_sched(void)
+{
+	_rcu_barrier(&rcu_sched_state, call_rcu_sched);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+
+/*
+ * Do boot-time initialization of a CPU's per-CPU RCU data.
+ */
+static void __init
+rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
+{
+	unsigned long flags;
+	int i;
+	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+	struct rcu_node *rnp = rcu_get_root(rsp);
+
+	/* Set up local state, ensuring consistent view of global state. */
+	raw_spin_lock_irqsave(&rnp->lock, flags);
+	rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
+	rdp->nxtlist = NULL;
+	for (i = 0; i < RCU_NEXT_SIZE; i++)
+		rdp->nxttail[i] = &rdp->nxtlist;
+	rdp->qlen_lazy = 0;
+	rdp->qlen = 0;
+	rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
+	WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
+	WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
+	rdp->cpu = cpu;
+	rdp->rsp = rsp;
+	raw_spin_unlock_irqrestore(&rnp->lock, flags);
+}
+
+/*
+ * Initialize a CPU's per-CPU RCU data.  Note that only one online or
+ * offline event can be happening at a given time.  Note also that we
+ * can accept some slop in the rsp->completed access due to the fact
+ * that this CPU cannot possibly have any RCU callbacks in flight yet.
+ */
+static void __cpuinit
+rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
+{
+	unsigned long flags;
+	unsigned long mask;
+	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+	struct rcu_node *rnp = rcu_get_root(rsp);
+
+	/* Set up local state, ensuring consistent view of global state. */
+	raw_spin_lock_irqsave(&rnp->lock, flags);
+	rdp->beenonline = 1;	 /* We have now been online. */
+	rdp->preemptible = preemptible;
+	rdp->qlen_last_fqs_check = 0;
+	rdp->n_force_qs_snap = rsp->n_force_qs;
+	rdp->blimit = blimit;
+	rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+	atomic_set(&rdp->dynticks->dynticks,
+		   (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
+	rcu_prepare_for_idle_init(cpu);
+	raw_spin_unlock(&rnp->lock);		/* irqs remain disabled. */
+
+	/*
+	 * A new grace period might start here.  If so, we won't be part
+	 * of it, but that is OK, as we are currently in a quiescent state.
+	 */
+
+	/* Exclude any attempts to start a new GP on large systems. */
+	raw_spin_lock(&rsp->onofflock);		/* irqs already disabled. */
+
+	/* Add CPU to rcu_node bitmasks. */
+	rnp = rdp->mynode;
+	mask = rdp->grpmask;
+	do {
+		/* Exclude any attempts to start a new GP on small systems. */
+		raw_spin_lock(&rnp->lock);	/* irqs already disabled. */
+		rnp->qsmaskinit |= mask;
+		mask = rnp->grpmask;
+		if (rnp == rdp->mynode) {
+			/*
+			 * If there is a grace period in progress, we will
+			 * set up to wait for it next time we run the
+			 * RCU core code.
+			 */
+			rdp->gpnum = rnp->completed;
+			rdp->completed = rnp->completed;
+			rdp->passed_quiesce = 0;
+			rdp->qs_pending = 0;
+			rdp->passed_quiesce_gpnum = rnp->gpnum - 1;
+			trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl");
+		}
+		raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
+		rnp = rnp->parent;
+	} while (rnp != NULL && !(rnp->qsmaskinit & mask));
+
+	raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
+}
+
+static void __cpuinit rcu_prepare_cpu(int cpu)
+{
+	rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
+	rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
+	rcu_preempt_init_percpu_data(cpu);
+}
+
+/*
+ * Handle CPU online/offline notification events.
+ */
+static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
+				    unsigned long action, void *hcpu)
+{
+	long cpu = (long)hcpu;
+	struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
+	struct rcu_node *rnp = rdp->mynode;
+
+	trace_rcu_utilization("Start CPU hotplug");
+	switch (action) {
+	case CPU_UP_PREPARE:
+	case CPU_UP_PREPARE_FROZEN:
+		rcu_prepare_cpu(cpu);
+		rcu_prepare_kthreads(cpu);
+		break;
+	case CPU_ONLINE:
+	case CPU_DOWN_FAILED:
+		rcu_node_kthread_setaffinity(rnp, -1);
+		rcu_cpu_kthread_setrt(cpu, 1);
+		break;
+	case CPU_DOWN_PREPARE:
+		rcu_node_kthread_setaffinity(rnp, cpu);
+		rcu_cpu_kthread_setrt(cpu, 0);
+		break;
+	case CPU_DYING:
+	case CPU_DYING_FROZEN:
+		/*
+		 * The whole machine is "stopped" except this CPU, so we can
+		 * touch any data without introducing corruption. We send the
+		 * dying CPU's callbacks to an arbitrarily chosen online CPU.
+		 */
+		rcu_cleanup_dying_cpu(&rcu_bh_state);
+		rcu_cleanup_dying_cpu(&rcu_sched_state);
+		rcu_preempt_cleanup_dying_cpu();
+		rcu_cleanup_after_idle(cpu);
+		break;
+	case CPU_DEAD:
+	case CPU_DEAD_FROZEN:
+	case CPU_UP_CANCELED:
+	case CPU_UP_CANCELED_FROZEN:
+		rcu_cleanup_dead_cpu(cpu, &rcu_bh_state);
+		rcu_cleanup_dead_cpu(cpu, &rcu_sched_state);
+		rcu_preempt_cleanup_dead_cpu(cpu);
+		break;
+	default:
+		break;
+	}
+	trace_rcu_utilization("End CPU hotplug");
+	return NOTIFY_OK;
+}
+
+/*
+ * This function is invoked towards the end of the scheduler's initialization
+ * process.  Before this is called, the idle task might contain
+ * RCU read-side critical sections (during which time, this idle
+ * task is booting the system).  After this function is called, the
+ * idle tasks are prohibited from containing RCU read-side critical
+ * sections.  This function also enables RCU lockdep checking.
+ */
+void rcu_scheduler_starting(void)
+{
+	WARN_ON(num_online_cpus() != 1);
+	WARN_ON(nr_context_switches() > 0);
+	rcu_scheduler_active = 1;
+}
+
+/*
+ * Compute the per-level fanout, either using the exact fanout specified
+ * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
+ */
+#ifdef CONFIG_RCU_FANOUT_EXACT
+static void __init rcu_init_levelspread(struct rcu_state *rsp)
+{
+	int i;
+
+	for (i = NUM_RCU_LVLS - 1; i > 0; i--)
+		rsp->levelspread[i] = CONFIG_RCU_FANOUT;
+	rsp->levelspread[0] = RCU_FANOUT_LEAF;
+}
+#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
+static void __init rcu_init_levelspread(struct rcu_state *rsp)
+{
+	int ccur;
+	int cprv;
+	int i;
+
+	cprv = NR_CPUS;
+	for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
+		ccur = rsp->levelcnt[i];
+		rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
+		cprv = ccur;
+	}
+}
+#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
+
+/*
+ * Helper function for rcu_init() that initializes one rcu_state structure.
+ */
+static void __init rcu_init_one(struct rcu_state *rsp,
+		struct rcu_data __percpu *rda)
+{
+	static char *buf[] = { "rcu_node_level_0",
+			       "rcu_node_level_1",
+			       "rcu_node_level_2",
+			       "rcu_node_level_3" };  /* Match MAX_RCU_LVLS */
+	int cpustride = 1;
+	int i;
+	int j;
+	struct rcu_node *rnp;
+
+	BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf));  /* Fix buf[] init! */
+
+	/* Initialize the level-tracking arrays. */
+
+	for (i = 1; i < NUM_RCU_LVLS; i++)
+		rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
+	rcu_init_levelspread(rsp);
+
+	/* Initialize the elements themselves, starting from the leaves. */
+
+	for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
+		cpustride *= rsp->levelspread[i];
+		rnp = rsp->level[i];
+		for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
+			raw_spin_lock_init(&rnp->lock);
+			lockdep_set_class_and_name(&rnp->lock,
+						   &rcu_node_class[i], buf[i]);
+			rnp->gpnum = 0;
+			rnp->qsmask = 0;
+			rnp->qsmaskinit = 0;
+			rnp->grplo = j * cpustride;
+			rnp->grphi = (j + 1) * cpustride - 1;
+			if (rnp->grphi >= NR_CPUS)
+				rnp->grphi = NR_CPUS - 1;
+			if (i == 0) {
+				rnp->grpnum = 0;
+				rnp->grpmask = 0;
+				rnp->parent = NULL;
+			} else {
+				rnp->grpnum = j % rsp->levelspread[i - 1];
+				rnp->grpmask = 1UL << rnp->grpnum;
+				rnp->parent = rsp->level[i - 1] +
+					      j / rsp->levelspread[i - 1];
+			}
+			rnp->level = i;
+			INIT_LIST_HEAD(&rnp->blkd_tasks);
+		}
+	}
+
+	rsp->rda = rda;
+	rnp = rsp->level[NUM_RCU_LVLS - 1];
+	for_each_possible_cpu(i) {
+		while (i > rnp->grphi)
+			rnp++;
+		per_cpu_ptr(rsp->rda, i)->mynode = rnp;
+		rcu_boot_init_percpu_data(i, rsp);
+	}
+}
+
+void __init rcu_init(void)
+{
+	int cpu;
+
+	rcu_bootup_announce();
+	rcu_init_one(&rcu_sched_state, &rcu_sched_data);
+	rcu_init_one(&rcu_bh_state, &rcu_bh_data);
+	__rcu_init_preempt();
+	 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+
+	/*
+	 * We don't need protection against CPU-hotplug here because
+	 * this is called early in boot, before either interrupts
+	 * or the scheduler are operational.
+	 */
+	cpu_notifier(rcu_cpu_notify, 0);
+	for_each_online_cpu(cpu)
+		rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
+	check_cpu_stall_init();
+}
+
+#include "rcutree_plugin.h"