rcu: Move RCU-related source code to kernel/rcu directory

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 0 insertions, 2831 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
deleted file mode 100644
index 8d85a5ce093a..000000000000
--- a/kernel/rcutree_plugin.h
+++ /dev/null
@@ -1,2831 +0,0 @@
-/*
- * Read-Copy Update mechanism for mutual exclusion (tree-based version)
- * Internal non-public definitions that provide either classic
- * or preemptible semantics.
- *
- * 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 Red Hat, 2009
- * Copyright IBM Corporation, 2009
- *
- * Author: Ingo Molnar <mingo@elte.hu>
- *	   Paul E. McKenney <paulmck@linux.vnet.ibm.com>
- */
-
-#include <linux/delay.h>
-#include <linux/gfp.h>
-#include <linux/oom.h>
-#include <linux/smpboot.h>
-#include "time/tick-internal.h"
-
-#define RCU_KTHREAD_PRIO 1
-
-#ifdef CONFIG_RCU_BOOST
-#define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO
-#else
-#define RCU_BOOST_PRIO RCU_KTHREAD_PRIO
-#endif
-
-#ifdef CONFIG_RCU_NOCB_CPU
-static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
-static bool have_rcu_nocb_mask;	    /* Was rcu_nocb_mask allocated? */
-static bool __read_mostly rcu_nocb_poll;    /* Offload kthread are to poll. */
-static char __initdata nocb_buf[NR_CPUS * 5];
-#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
-
-/*
- * Check the RCU kernel configuration parameters and print informative
- * messages about anything out of the ordinary.  If you like #ifdef, you
- * will love this function.
- */
-static void __init rcu_bootup_announce_oddness(void)
-{
-#ifdef CONFIG_RCU_TRACE
-	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)
-	pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n",
-	       CONFIG_RCU_FANOUT);
-#endif
-#ifdef CONFIG_RCU_FANOUT_EXACT
-	pr_info("\tHierarchical RCU autobalancing is disabled.\n");
-#endif
-#ifdef CONFIG_RCU_FAST_NO_HZ
-	pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
-#endif
-#ifdef CONFIG_PROVE_RCU
-	pr_info("\tRCU lockdep checking is enabled.\n");
-#endif
-#ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE
-	pr_info("\tRCU torture testing starts during boot.\n");
-#endif
-#if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE)
-	pr_info("\tDump stacks of tasks blocking RCU-preempt GP.\n");
-#endif
-#if defined(CONFIG_RCU_CPU_STALL_INFO)
-	pr_info("\tAdditional per-CPU info printed with stalls.\n");
-#endif
-#if NUM_RCU_LVL_4 != 0
-	pr_info("\tFour-level hierarchy is enabled.\n");
-#endif
-	if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF)
-		pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
-	if (nr_cpu_ids != NR_CPUS)
-		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) {
-		zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL);
-		have_rcu_nocb_mask = true;
-	}
-#ifdef CONFIG_RCU_NOCB_CPU_ZERO
-	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("\tOffload RCU callbacks from all CPUs\n");
-	cpumask_copy(rcu_nocb_mask, cpu_possible_mask);
-#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
-#endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */
-	if (have_rcu_nocb_mask) {
-		if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
-			pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n");
-			cpumask_and(rcu_nocb_mask, cpu_possible_mask,
-				    rcu_nocb_mask);
-		}
-		cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask);
-		pr_info("\tOffload RCU callbacks from CPUs: %s.\n", nocb_buf);
-		if (rcu_nocb_poll)
-			pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
-	}
-#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
-}
-
-#ifdef CONFIG_TREE_PREEMPT_RCU
-
-RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
-static struct rcu_state *rcu_state = &rcu_preempt_state;
-
-static int rcu_preempted_readers_exp(struct rcu_node *rnp);
-
-/*
- * Tell them what RCU they are running.
- */
-static void __init rcu_bootup_announce(void)
-{
-	pr_info("Preemptible hierarchical RCU implementation.\n");
-	rcu_bootup_announce_oddness();
-}
-
-/*
- * Return the number of RCU-preempt batches processed thus far
- * for debug and statistics.
- */
-long rcu_batches_completed_preempt(void)
-{
-	return rcu_preempt_state.completed;
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt);
-
-/*
- * Return the number of RCU batches processed thus far for debug & stats.
- */
-long rcu_batches_completed(void)
-{
-	return rcu_batches_completed_preempt();
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed);
-
-/*
- * Force a quiescent state for preemptible RCU.
- */
-void rcu_force_quiescent_state(void)
-{
-	force_quiescent_state(&rcu_preempt_state);
-}
-EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
-
-/*
- * Record a preemptible-RCU quiescent state for the specified CPU.  Note
- * that this just means that the task currently running on the CPU is
- * not 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.
- */
-static void rcu_preempt_qs(int cpu)
-{
-	struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
-
-	if (rdp->passed_quiesce == 0)
-		trace_rcu_grace_period(TPS("rcu_preempt"), rdp->gpnum, TPS("cpuqs"));
-	rdp->passed_quiesce = 1;
-	current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_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.
- * 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 blkd_tasks list entries
- * predating the current grace period drain, in other words, until
- * rnp->gp_tasks becomes NULL.
- *
- * Caller must disable preemption.
- */
-static void rcu_preempt_note_context_switch(int cpu)
-{
-	struct task_struct *t = current;
-	unsigned long flags;
-	struct rcu_data *rdp;
-	struct rcu_node *rnp;
-
-	if (t->rcu_read_lock_nesting > 0 &&
-	    (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
-
-		/* Possibly blocking in an RCU read-side critical section. */
-		rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu);
-		rnp = rdp->mynode;
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
-		t->rcu_blocked_node = rnp;
-
-		/*
-		 * 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.  Note that there is some uncertainty as
-		 * to exactly when the current grace period started.
-		 * We take a conservative approach, which can result
-		 * in unnecessarily waiting on tasks that started very
-		 * slightly after the current grace period began.  C'est
-		 * la vie!!!
-		 *
-		 * But first, note that the current CPU must still be
-		 * on line!
-		 */
-		WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0);
-		WARN_ON_ONCE(!list_empty(&t->rcu_node_entry));
-		if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) {
-			list_add(&t->rcu_node_entry, rnp->gp_tasks->prev);
-			rnp->gp_tasks = &t->rcu_node_entry;
-#ifdef CONFIG_RCU_BOOST
-			if (rnp->boost_tasks != NULL)
-				rnp->boost_tasks = rnp->gp_tasks;
-#endif /* #ifdef CONFIG_RCU_BOOST */
-		} else {
-			list_add(&t->rcu_node_entry, &rnp->blkd_tasks);
-			if (rnp->qsmask & rdp->grpmask)
-				rnp->gp_tasks = &t->rcu_node_entry;
-		}
-		trace_rcu_preempt_task(rdp->rsp->name,
-				       t->pid,
-				       (rnp->qsmask & rdp->grpmask)
-				       ? rnp->gpnum
-				       : rnp->gpnum + 1);
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-	} else if (t->rcu_read_lock_nesting < 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 we continue to block the current grace period.
-	 */
-	local_irq_save(flags);
-	rcu_preempt_qs(cpu);
-	local_irq_restore(flags);
-}
-
-/*
- * Check for preempted RCU readers blocking the current grace period
- * for the specified rcu_node structure.  If the caller needs a reliable
- * answer, it must hold the rcu_node's ->lock.
- */
-static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
-{
-	return rnp->gp_tasks != NULL;
-}
-
-/*
- * Record a quiescent state for all tasks that were previously queued
- * on the specified rcu_node structure and that were blocking the current
- * RCU grace period.  The caller must hold the specified rnp->lock with
- * irqs disabled, and this lock is released upon return, but irqs remain
- * disabled.
- */
-static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
-	__releases(rnp->lock)
-{
-	unsigned long mask;
-	struct rcu_node *rnp_p;
-
-	if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-		return;  /* Still need more quiescent states! */
-	}
-
-	rnp_p = rnp->parent;
-	if (rnp_p == NULL) {
-		/*
-		 * Either there is only one rcu_node in the tree,
-		 * or tasks were kicked up to root rcu_node due to
-		 * CPUs going offline.
-		 */
-		rcu_report_qs_rsp(&rcu_preempt_state, flags);
-		return;
-	}
-
-	/* Report up the rest of the hierarchy. */
-	mask = rnp->grpmask;
-	raw_spin_unlock(&rnp->lock);	/* irqs remain disabled. */
-	raw_spin_lock(&rnp_p->lock);	/* irqs already disabled. */
-	rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags);
-}
-
-/*
- * 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 rcu_node *rnp)
-{
-	struct list_head *np;
-
-	np = t->rcu_node_entry.next;
-	if (np == &rnp->blkd_tasks)
-		np = NULL;
-	return np;
-}
-
-/*
- * 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;
-	int empty_exp_now;
-	unsigned long flags;
-	struct list_head *np;
-#ifdef CONFIG_RCU_BOOST
-	struct rt_mutex *rbmp = NULL;
-#endif /* #ifdef CONFIG_RCU_BOOST */
-	struct rcu_node *rnp;
-	int special;
-
-	/* NMI handlers cannot block and cannot safely manipulate state. */
-	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_qs(smp_processor_id());
-	}
-
-	/* 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 list it blocked on.  The
-		 * task can migrate while we acquire the lock, but at
-		 * most one time.  So at most two passes through loop.
-		 */
-		for (;;) {
-			rnp = t->rcu_blocked_node;
-			raw_spin_lock(&rnp->lock);  /* irqs already disabled. */
-			if (rnp == t->rcu_blocked_node)
-				break;
-			raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
-		}
-		empty = !rcu_preempt_blocked_readers_cgp(rnp);
-		empty_exp = !rcu_preempted_readers_exp(rnp);
-		smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
-		np = rcu_next_node_entry(t, rnp);
-		list_del_init(&t->rcu_node_entry);
-		t->rcu_blocked_node = NULL;
-		trace_rcu_unlock_preempted_task(TPS("rcu_preempt"),
-						rnp->gpnum, t->pid);
-		if (&t->rcu_node_entry == rnp->gp_tasks)
-			rnp->gp_tasks = np;
-		if (&t->rcu_node_entry == rnp->exp_tasks)
-			rnp->exp_tasks = np;
-#ifdef CONFIG_RCU_BOOST
-		if (&t->rcu_node_entry == rnp->boost_tasks)
-			rnp->boost_tasks = np;
-		/* Snapshot/clear ->rcu_boost_mutex with rcu_node lock held. */
-		if (t->rcu_boost_mutex) {
-			rbmp = t->rcu_boost_mutex;
-			t->rcu_boost_mutex = NULL;
-		}
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
-		/*
-		 * If this was the last task on the current list, and if
-		 * we aren't waiting on any CPUs, report the quiescent state.
-		 * Note that rcu_report_unblock_qs_rnp() releases rnp->lock,
-		 * so we must take a snapshot of the expedited state.
-		 */
-		empty_exp_now = !rcu_preempted_readers_exp(rnp);
-		if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) {
-			trace_rcu_quiescent_state_report(TPS("preempt_rcu"),
-							 rnp->gpnum,
-							 0, rnp->qsmask,
-							 rnp->level,
-							 rnp->grplo,
-							 rnp->grphi,
-							 !!rnp->gp_tasks);
-			rcu_report_unblock_qs_rnp(rnp, flags);
-		} else {
-			raw_spin_unlock_irqrestore(&rnp->lock, flags);
-		}
-
-#ifdef CONFIG_RCU_BOOST
-		/* Unboost if we were boosted. */
-		if (rbmp)
-			rt_mutex_unlock(rbmp);
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
-		/*
-		 * If this was the last task on the expedited lists,
-		 * then we need to report up the rcu_node hierarchy.
-		 */
-		if (!empty_exp && empty_exp_now)
-			rcu_report_exp_rnp(&rcu_preempt_state, rnp, true);
-	} else {
-		local_irq_restore(flags);
-	}
-}
-
-#ifdef CONFIG_RCU_CPU_STALL_VERBOSE
-
-/*
- * Dump detailed information for all tasks blocking the current RCU
- * grace period on the specified rcu_node structure.
- */
-static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
-{
-	unsigned long flags;
-	struct task_struct *t;
-
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	if (!rcu_preempt_blocked_readers_cgp(rnp)) {
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-		return;
-	}
-	t = list_entry(rnp->gp_tasks,
-		       struct task_struct, rcu_node_entry);
-	list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry)
-		sched_show_task(t);
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-}
-
-/*
- * Dump detailed information for all tasks blocking the current RCU
- * grace period.
- */
-static void rcu_print_detail_task_stall(struct rcu_state *rsp)
-{
-	struct rcu_node *rnp = rcu_get_root(rsp);
-
-	rcu_print_detail_task_stall_rnp(rnp);
-	rcu_for_each_leaf_node(rsp, rnp)
-		rcu_print_detail_task_stall_rnp(rnp);
-}
-
-#else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
-
-static void rcu_print_detail_task_stall(struct rcu_state *rsp)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
-
-#ifdef CONFIG_RCU_CPU_STALL_INFO
-
-static void rcu_print_task_stall_begin(struct rcu_node *rnp)
-{
-	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)
-{
-	pr_cont("\n");
-}
-
-#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
-
-static void rcu_print_task_stall_begin(struct rcu_node *rnp)
-{
-}
-
-static void rcu_print_task_stall_end(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */
-
-/*
- * Scan the current list of tasks blocked within RCU read-side critical
- * sections, printing out the tid of each.
- */
-static int rcu_print_task_stall(struct rcu_node *rnp)
-{
-	struct task_struct *t;
-	int ndetected = 0;
-
-	if (!rcu_preempt_blocked_readers_cgp(rnp))
-		return 0;
-	rcu_print_task_stall_begin(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) {
-		pr_cont(" P%d", t->pid);
-		ndetected++;
-	}
-	rcu_print_task_stall_end();
-	return ndetected;
-}
-
-/*
- * Check that the list of blocked tasks for the newly completed grace
- * period is in fact empty.  It is a serious bug to complete a grace
- * period that still has RCU readers blocked!  This function must be
- * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock
- * must be held by the caller.
- *
- * Also, if there are blocked tasks on the list, they automatically
- * block the newly created grace period, so set up ->gp_tasks accordingly.
- */
-static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
-{
-	WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
-	if (!list_empty(&rnp->blkd_tasks))
-		rnp->gp_tasks = rnp->blkd_tasks.next;
-	WARN_ON_ONCE(rnp->qsmask);
-}
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Handle tasklist migration for case in which all CPUs covered by the
- * specified rcu_node have gone offline.  Move them up to the root
- * rcu_node.  The reason for not just moving them to the immediate
- * parent is to remove the need for rcu_read_unlock_special() to
- * make more than two attempts to acquire the target rcu_node's lock.
- * Returns true if there were tasks blocking the current RCU grace
- * period.
- *
- * Returns 1 if there was previously a task blocking the current grace
- * period on the specified rcu_node structure.
- *
- * The caller must hold rnp->lock with irqs disabled.
- */
-static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
-				     struct rcu_node *rnp,
-				     struct rcu_data *rdp)
-{
-	struct list_head *lp;
-	struct list_head *lp_root;
-	int retval = 0;
-	struct rcu_node *rnp_root = rcu_get_root(rsp);
-	struct task_struct *t;
-
-	if (rnp == rnp_root) {
-		WARN_ONCE(1, "Last CPU thought to be offlined?");
-		return 0;  /* Shouldn't happen: at least one CPU online. */
-	}
-
-	/* If we are on an internal node, complain bitterly. */
-	WARN_ON_ONCE(rnp != rdp->mynode);
-
-	/*
-	 * Move tasks up to root rcu_node.  Don't try to get fancy for
-	 * this corner-case operation -- just put this node's tasks
-	 * at the head of the root node's list, and update the root node's
-	 * ->gp_tasks and ->exp_tasks pointers to those of this node's,
-	 * if non-NULL.  This might result in waiting for more tasks than
-	 * absolutely necessary, but this is a good performance/complexity
-	 * tradeoff.
-	 */
-	if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0)
-		retval |= RCU_OFL_TASKS_NORM_GP;
-	if (rcu_preempted_readers_exp(rnp))
-		retval |= RCU_OFL_TASKS_EXP_GP;
-	lp = &rnp->blkd_tasks;
-	lp_root = &rnp_root->blkd_tasks;
-	while (!list_empty(lp)) {
-		t = list_entry(lp->next, typeof(*t), rcu_node_entry);
-		raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
-		list_del(&t->rcu_node_entry);
-		t->rcu_blocked_node = rnp_root;
-		list_add(&t->rcu_node_entry, lp_root);
-		if (&t->rcu_node_entry == rnp->gp_tasks)
-			rnp_root->gp_tasks = rnp->gp_tasks;
-		if (&t->rcu_node_entry == rnp->exp_tasks)
-			rnp_root->exp_tasks = rnp->exp_tasks;
-#ifdef CONFIG_RCU_BOOST
-		if (&t->rcu_node_entry == rnp->boost_tasks)
-			rnp_root->boost_tasks = rnp->boost_tasks;
-#endif /* #ifdef CONFIG_RCU_BOOST */
-		raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
-	}
-
-	rnp->gp_tasks = NULL;
-	rnp->exp_tasks = NULL;
-#ifdef CONFIG_RCU_BOOST
-	rnp->boost_tasks = NULL;
-	/*
-	 * In case root is being boosted and leaf was not.  Make sure
-	 * that we boost the tasks blocking the current grace period
-	 * in this case.
-	 */
-	raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
-	if (rnp_root->boost_tasks != NULL &&
-	    rnp_root->boost_tasks != rnp_root->gp_tasks &&
-	    rnp_root->boost_tasks != rnp_root->exp_tasks)
-		rnp_root->boost_tasks = rnp_root->gp_tasks;
-	raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
-	return retval;
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
-/*
- * Check for a quiescent state from the current CPU.  When a task blocks,
- * the task is recorded in the corresponding CPU's rcu_node structure,
- * which is checked elsewhere.
- *
- * Caller must disable hard irqs.
- */
-static void rcu_preempt_check_callbacks(int cpu)
-{
-	struct task_struct *t = current;
-
-	if (t->rcu_read_lock_nesting == 0) {
-		rcu_preempt_qs(cpu);
-		return;
-	}
-	if (t->rcu_read_lock_nesting > 0 &&
-	    per_cpu(rcu_preempt_data, cpu).qs_pending)
-		t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
-}
-
-#ifdef CONFIG_RCU_BOOST
-
-static void rcu_preempt_do_callbacks(void)
-{
-	rcu_do_batch(&rcu_preempt_state, this_cpu_ptr(&rcu_preempt_data));
-}
-
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
-/*
- * Queue a preemptible-RCU callback for invocation after a grace period.
- */
-void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
-{
-	__call_rcu(head, func, &rcu_preempt_state, -1, 0);
-}
-EXPORT_SYMBOL_GPL(call_rcu);
-
-/*
- * Queue an RCU callback for lazy invocation after a grace period.
- * This will likely be later named something like "call_rcu_lazy()",
- * but this change will require some way of tagging the lazy RCU
- * callbacks in the list of pending callbacks.  Until then, this
- * function may only be called from __kfree_rcu().
- */
-void kfree_call_rcu(struct rcu_head *head,
-		    void (*func)(struct rcu_head *rcu))
-{
-	__call_rcu(head, func, &rcu_preempt_state, -1, 1);
-}
-EXPORT_SYMBOL_GPL(kfree_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.  Note, however, that
- * upon return from synchronize_rcu(), the caller might well be executing
- * concurrently with new RCU read-side critical sections that began while
- * synchronize_rcu() was waiting.  RCU read-side critical sections are
- * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested.
- *
- * See the description of synchronize_sched() for more detailed information
- * on memory ordering guarantees.
- */
-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");
-	if (!rcu_scheduler_active)
-		return;
-	if (rcu_expedited)
-		synchronize_rcu_expedited();
-	else
-		wait_rcu_gp(call_rcu);
-}
-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(struct rcu_node *rnp)
-{
-	return rnp->exp_tasks != NULL;
-}
-
-/*
- * return non-zero if there is no RCU expedited grace period in progress
- * for the specified rcu_node structure, in other words, if all CPUs and
- * tasks covered by the specified rcu_node structure have done their bit
- * for the current expedited grace period.  Works only for preemptible
- * RCU -- other RCU implementation use other means.
- *
- * Caller must hold sync_rcu_preempt_exp_mutex.
- */
-static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
-{
-	return !rcu_preempted_readers_exp(rnp) &&
-	       ACCESS_ONCE(rnp->expmask) == 0;
-}
-
-/*
- * 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.  This event is reported either to the rcu_node structure on
- * which the task was queued or to one of that rcu_node structure's ancestors,
- * recursively up the tree.  (Calm down, calm down, we do the recursion
- * iteratively!)
- *
- * Most callers will set the "wake" flag, but the task initiating the
- * expedited grace period need not wake itself.
- *
- * Caller must hold sync_rcu_preempt_exp_mutex.
- */
-static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
-			       bool wake)
-{
-	unsigned long flags;
-	unsigned long mask;
-
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	for (;;) {
-		if (!sync_rcu_preempt_exp_done(rnp)) {
-			raw_spin_unlock_irqrestore(&rnp->lock, flags);
-			break;
-		}
-		if (rnp->parent == NULL) {
-			raw_spin_unlock_irqrestore(&rnp->lock, flags);
-			if (wake)
-				wake_up(&sync_rcu_preempt_exp_wq);
-			break;
-		}
-		mask = rnp->grpmask;
-		raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
-		rnp = rnp->parent;
-		raw_spin_lock(&rnp->lock); /* irqs already disabled */
-		rnp->expmask &= ~mask;
-	}
-}
-
-/*
- * Snapshot the tasks blocking the newly started preemptible-RCU expedited
- * grace period for the specified rcu_node structure.  If there are no such
- * tasks, report it up the rcu_node hierarchy.
- *
- * Caller must hold sync_rcu_preempt_exp_mutex and must exclude
- * CPU hotplug operations.
- */
-static void
-sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
-{
-	unsigned long flags;
-	int must_wait = 0;
-
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	if (list_empty(&rnp->blkd_tasks)) {
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-	} else {
-		rnp->exp_tasks = rnp->blkd_tasks.next;
-		rcu_initiate_boost(rnp, flags);  /* releases rnp->lock */
-		must_wait = 1;
-	}
-	if (!must_wait)
-		rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */
-}
-
-/**
- * synchronize_rcu_expedited - Brute-force RCU grace period
- *
- * Wait for an RCU-preempt grace period, but expedite it.  The basic
- * idea is to invoke synchronize_sched_expedited() to push all the tasks to
- * the ->blkd_tasks lists and wait for this list to drain.  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_rcu_expedited() in a loop,
- * please restructure your code to batch your updates, and then Use a
- * single synchronize_rcu() 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.
- */
-void synchronize_rcu_expedited(void)
-{
-	unsigned long flags;
-	struct rcu_node *rnp;
-	struct rcu_state *rsp = &rcu_preempt_state;
-	unsigned long snap;
-	int trycount = 0;
-
-	smp_mb(); /* Caller's modifications seen first by other CPUs. */
-	snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1;
-	smp_mb(); /* Above access cannot bleed into critical section. */
-
-	/*
-	 * Block CPU-hotplug operations.  This means that any CPU-hotplug
-	 * operation that finds an rcu_node structure with tasks in the
-	 * process of being boosted will know that all tasks blocking
-	 * this expedited grace period will already be in the process of
-	 * being boosted.  This simplifies the process of moving tasks
-	 * from leaf to root rcu_node structures.
-	 */
-	get_online_cpus();
-
-	/*
-	 * Acquire lock, falling back to synchronize_rcu() if too many
-	 * lock-acquisition failures.  Of course, if someone does the
-	 * expedited grace period for us, just leave.
-	 */
-	while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) {
-		if (ULONG_CMP_LT(snap,
-		    ACCESS_ONCE(sync_rcu_preempt_exp_count))) {
-			put_online_cpus();
-			goto mb_ret; /* Others did our work for us. */
-		}
-		if (trycount++ < 10) {
-			udelay(trycount * num_online_cpus());
-		} else {
-			put_online_cpus();
-			wait_rcu_gp(call_rcu);
-			return;
-		}
-	}
-	if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) {
-		put_online_cpus();
-		goto unlock_mb_ret; /* Others did our work for us. */
-	}
-
-	/* force all RCU readers onto ->blkd_tasks lists. */
-	synchronize_sched_expedited();
-
-	/* Initialize ->expmask for all non-leaf rcu_node structures. */
-	rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) {
-		raw_spin_lock_irqsave(&rnp->lock, flags);
-		rnp->expmask = rnp->qsmaskinit;
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-	}
-
-	/* Snapshot current state of ->blkd_tasks lists. */
-	rcu_for_each_leaf_node(rsp, rnp)
-		sync_rcu_preempt_exp_init(rsp, rnp);
-	if (NUM_RCU_NODES > 1)
-		sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp));
-
-	put_online_cpus();
-
-	/* Wait for snapshotted ->blkd_tasks lists to drain. */
-	rnp = rcu_get_root(rsp);
-	wait_event(sync_rcu_preempt_exp_wq,
-		   sync_rcu_preempt_exp_done(rnp));
-
-	/* Clean up and exit. */
-	smp_mb(); /* ensure expedited GP seen before counter increment. */
-	ACCESS_ONCE(sync_rcu_preempt_exp_count)++;
-unlock_mb_ret:
-	mutex_unlock(&sync_rcu_preempt_exp_mutex);
-mb_ret:
-	smp_mb(); /* ensure subsequent action seen after grace period. */
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
-
-/**
- * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
- *
- * Note that this primitive does not necessarily wait for an RCU grace period
- * to complete.  For example, if there are no RCU callbacks queued anywhere
- * in the system, then rcu_barrier() is within its rights to return
- * immediately, without waiting for anything, much less an RCU grace period.
- */
-void rcu_barrier(void)
-{
-	_rcu_barrier(&rcu_preempt_state);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier);
-
-/*
- * Initialize preemptible RCU's state structures.
- */
-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;
-
-/*
- * Tell them what RCU they are running.
- */
-static void __init rcu_bootup_announce(void)
-{
-	pr_info("Hierarchical RCU implementation.\n");
-	rcu_bootup_announce_oddness();
-}
-
-/*
- * Return the number of RCU batches processed thus far for debug & stats.
- */
-long rcu_batches_completed(void)
-{
-	return rcu_batches_completed_sched();
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed);
-
-/*
- * Force a quiescent state for RCU, which, because there is no preemptible
- * RCU, becomes the same as rcu-sched.
- */
-void rcu_force_quiescent_state(void)
-{
-	rcu_sched_force_quiescent_state();
-}
-EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
-
-/*
- * Because preemptible RCU does not exist, we never have to check for
- * CPUs being in quiescent states.
- */
-static void rcu_preempt_note_context_switch(int cpu)
-{
-}
-
-/*
- * Because preemptible RCU does not exist, there are never any preempted
- * RCU readers.
- */
-static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
-{
-	return 0;
-}
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/* Because preemptible RCU does not exist, no quieting of tasks. */
-static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
-{
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
-/*
- * Because preemptible RCU does not exist, we never have to check for
- * tasks blocked within RCU read-side critical sections.
- */
-static void rcu_print_detail_task_stall(struct rcu_state *rsp)
-{
-}
-
-/*
- * Because preemptible RCU does not exist, we never have to check for
- * tasks blocked within RCU read-side critical sections.
- */
-static int rcu_print_task_stall(struct rcu_node *rnp)
-{
-	return 0;
-}
-
-/*
- * Because there is no preemptible RCU, there can be no readers blocked,
- * so there is no need to check for blocked tasks.  So check only for
- * bogus qsmask values.
- */
-static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
-{
-	WARN_ON_ONCE(rnp->qsmask);
-}
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Because preemptible RCU does not exist, it never needs to migrate
- * tasks that were blocked within RCU read-side critical sections, and
- * such non-existent tasks cannot possibly have been blocking the current
- * grace period.
- */
-static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
-				     struct rcu_node *rnp,
-				     struct rcu_data *rdp)
-{
-	return 0;
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
-/*
- * Because preemptible RCU does not exist, it never has any callbacks
- * to check.
- */
-static void rcu_preempt_check_callbacks(int cpu)
-{
-}
-
-/*
- * Queue an RCU callback for lazy invocation after a grace period.
- * This will likely be later named something like "call_rcu_lazy()",
- * but this change will require some way of tagging the lazy RCU
- * callbacks in the list of pending callbacks.  Until then, this
- * function may only be called from __kfree_rcu().
- *
- * Because there is no preemptible RCU, we use RCU-sched instead.
- */
-void kfree_call_rcu(struct rcu_head *head,
-		    void (*func)(struct rcu_head *rcu))
-{
-	__call_rcu(head, func, &rcu_sched_state, -1, 1);
-}
-EXPORT_SYMBOL_GPL(kfree_call_rcu);
-
-/*
- * Wait for an rcu-preempt grace period, but make it happen quickly.
- * But because preemptible RCU does not exist, map to rcu-sched.
- */
-void synchronize_rcu_expedited(void)
-{
-	synchronize_sched_expedited();
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Because preemptible RCU does not exist, there is never any need to
- * report on tasks preempted in RCU read-side critical sections during
- * expedited RCU grace periods.
- */
-static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
-			       bool wake)
-{
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
-/*
- * Because preemptible RCU does not exist, rcu_barrier() is just
- * another name for rcu_barrier_sched().
- */
-void rcu_barrier(void)
-{
-	rcu_barrier_sched();
-}
-EXPORT_SYMBOL_GPL(rcu_barrier);
-
-/*
- * Because preemptible RCU does not exist, it need not be initialized.
- */
-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
-
-#include "rtmutex_common.h"
-
-#ifdef CONFIG_RCU_TRACE
-
-static void rcu_initiate_boost_trace(struct rcu_node *rnp)
-{
-	if (list_empty(&rnp->blkd_tasks))
-		rnp->n_balk_blkd_tasks++;
-	else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL)
-		rnp->n_balk_exp_gp_tasks++;
-	else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL)
-		rnp->n_balk_boost_tasks++;
-	else if (rnp->gp_tasks != NULL && rnp->qsmask != 0)
-		rnp->n_balk_notblocked++;
-	else if (rnp->gp_tasks != NULL &&
-		 ULONG_CMP_LT(jiffies, rnp->boost_time))
-		rnp->n_balk_notyet++;
-	else
-		rnp->n_balk_nos++;
-}
-
-#else /* #ifdef CONFIG_RCU_TRACE */
-
-static void rcu_initiate_boost_trace(struct rcu_node *rnp)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_TRACE */
-
-static void rcu_wake_cond(struct task_struct *t, int status)
-{
-	/*
-	 * If the thread is yielding, only wake it when this
-	 * is invoked from idle
-	 */
-	if (status != RCU_KTHREAD_YIELDING || is_idle_task(current))
-		wake_up_process(t);
-}
-
-/*
- * Carry out RCU priority boosting on the task indicated by ->exp_tasks
- * or ->boost_tasks, advancing the pointer to the next task in the
- * ->blkd_tasks list.
- *
- * Note that irqs must be enabled: boosting the task can block.
- * Returns 1 if there are more tasks needing to be boosted.
- */
-static int rcu_boost(struct rcu_node *rnp)
-{
-	unsigned long flags;
-	struct rt_mutex mtx;
-	struct task_struct *t;
-	struct list_head *tb;
-
-	if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL)
-		return 0;  /* Nothing left to boost. */
-
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-
-	/*
-	 * Recheck under the lock: all tasks in need of boosting
-	 * might exit their RCU read-side critical sections on their own.
-	 */
-	if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) {
-		raw_spin_unlock_irqrestore(&rnp->lock, 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 (rnp->exp_tasks != NULL) {
-		tb = rnp->exp_tasks;
-		rnp->n_exp_boosts++;
-	} else {
-		tb = rnp->boost_tasks;
-		rnp->n_normal_boosts++;
-	}
-	rnp->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!)
-	 *
-	 * Note that task t must acquire rnp->lock to remove itself from
-	 * the ->blkd_tasks list, which it will do from exit() if from
-	 * nowhere else.  We therefore are guaranteed that task t will
-	 * stay around at least until we drop rnp->lock.  Note that
-	 * rnp->lock also resolves races between our priority boosting
-	 * and task t's exiting its outermost RCU read-side critical
-	 * section.
-	 */
-	t = container_of(tb, struct task_struct, rcu_node_entry);
-	rt_mutex_init_proxy_locked(&mtx, t);
-	t->rcu_boost_mutex = &mtx;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-	rt_mutex_lock(&mtx);  /* Side effect: boosts task t's priority. */
-	rt_mutex_unlock(&mtx);  /* Keep lockdep happy. */
-
-	return ACCESS_ONCE(rnp->exp_tasks) != NULL ||
-	       ACCESS_ONCE(rnp->boost_tasks) != NULL;
-}
-
-/*
- * Priority-boosting kthread.  One per leaf rcu_node and one for the
- * root rcu_node.
- */
-static int rcu_boost_kthread(void *arg)
-{
-	struct rcu_node *rnp = (struct rcu_node *)arg;
-	int spincnt = 0;
-	int more2boost;
-
-	trace_rcu_utilization(TPS("Start boost kthread@init"));
-	for (;;) {
-		rnp->boost_kthread_status = RCU_KTHREAD_WAITING;
-		trace_rcu_utilization(TPS("End boost kthread@rcu_wait"));
-		rcu_wait(rnp->boost_tasks || rnp->exp_tasks);
-		trace_rcu_utilization(TPS("Start boost kthread@rcu_wait"));
-		rnp->boost_kthread_status = RCU_KTHREAD_RUNNING;
-		more2boost = rcu_boost(rnp);
-		if (more2boost)
-			spincnt++;
-		else
-			spincnt = 0;
-		if (spincnt > 10) {
-			rnp->boost_kthread_status = RCU_KTHREAD_YIELDING;
-			trace_rcu_utilization(TPS("End boost kthread@rcu_yield"));
-			schedule_timeout_interruptible(2);
-			trace_rcu_utilization(TPS("Start boost kthread@rcu_yield"));
-			spincnt = 0;
-		}
-	}
-	/* NOTREACHED */
-	trace_rcu_utilization(TPS("End boost kthread@notreached"));
-	return 0;
-}
-
-/*
- * Check to see if it is time to start boosting RCU readers that are
- * blocking the current grace period, and, if so, tell the per-rcu_node
- * kthread to start boosting them.  If there is an expedited grace
- * period in progress, it is always time to boost.
- *
- * The caller must hold rnp->lock, which this function releases.
- * The ->boost_kthread_task is immortal, so we don't need to worry
- * about it going away.
- */
-static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
-{
-	struct task_struct *t;
-
-	if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) {
-		rnp->n_balk_exp_gp_tasks++;
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-		return;
-	}
-	if (rnp->exp_tasks != NULL ||
-	    (rnp->gp_tasks != NULL &&
-	     rnp->boost_tasks == NULL &&
-	     rnp->qsmask == 0 &&
-	     ULONG_CMP_GE(jiffies, rnp->boost_time))) {
-		if (rnp->exp_tasks == NULL)
-			rnp->boost_tasks = rnp->gp_tasks;
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-		t = rnp->boost_kthread_task;
-		if (t)
-			rcu_wake_cond(t, rnp->boost_kthread_status);
-	} else {
-		rcu_initiate_boost_trace(rnp);
-		raw_spin_unlock_irqrestore(&rnp->lock, flags);
-	}
-}
-
-/*
- * Wake up the per-CPU kthread to invoke RCU callbacks.
- */
-static void invoke_rcu_callbacks_kthread(void)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	__this_cpu_write(rcu_cpu_has_work, 1);
-	if (__this_cpu_read(rcu_cpu_kthread_task) != NULL &&
-	    current != __this_cpu_read(rcu_cpu_kthread_task)) {
-		rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task),
-			      __this_cpu_read(rcu_cpu_kthread_status));
-	}
-	local_irq_restore(flags);
-}
-
-/*
- * Is the current CPU running the RCU-callbacks kthread?
- * Caller must have preemption disabled.
- */
-static bool rcu_is_callbacks_kthread(void)
-{
-	return __this_cpu_read(rcu_cpu_kthread_task) == current;
-}
-
-#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(struct rcu_node *rnp)
-{
-	rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES;
-}
-
-/*
- * Create an RCU-boost kthread for the specified node if one does not
- * already exist.  We only create this kthread for preemptible RCU.
- * Returns zero if all is well, a negated errno otherwise.
- */
-static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
-						 struct rcu_node *rnp)
-{
-	int rnp_index = rnp - &rsp->node[0];
-	unsigned long flags;
-	struct sched_param sp;
-	struct task_struct *t;
-
-	if (&rcu_preempt_state != rsp)
-		return 0;
-
-	if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0)
-		return 0;
-
-	rsp->boost = 1;
-	if (rnp->boost_kthread_task != NULL)
-		return 0;
-	t = kthread_create(rcu_boost_kthread, (void *)rnp,
-			   "rcub/%d", rnp_index);
-	if (IS_ERR(t))
-		return PTR_ERR(t);
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	rnp->boost_kthread_task = t;
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-	sp.sched_priority = RCU_BOOST_PRIO;
-	sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
-	wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
-	return 0;
-}
-
-static void rcu_kthread_do_work(void)
-{
-	rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data));
-	rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data));
-	rcu_preempt_do_callbacks();
-}
-
-static void rcu_cpu_kthread_setup(unsigned int cpu)
-{
-	struct sched_param sp;
-
-	sp.sched_priority = RCU_KTHREAD_PRIO;
-	sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
-}
-
-static void rcu_cpu_kthread_park(unsigned int cpu)
-{
-	per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
-}
-
-static int rcu_cpu_kthread_should_run(unsigned int cpu)
-{
-	return __this_cpu_read(rcu_cpu_has_work);
-}
-
-/*
- * Per-CPU kernel thread that invokes RCU callbacks.  This replaces the
- * RCU softirq used in flavors and configurations of RCU that do not
- * support RCU priority boosting.
- */
-static void rcu_cpu_kthread(unsigned int cpu)
-{
-	unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status);
-	char work, *workp = this_cpu_ptr(&rcu_cpu_has_work);
-	int spincnt;
-
-	for (spincnt = 0; spincnt < 10; spincnt++) {
-		trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait"));
-		local_bh_disable();
-		*statusp = RCU_KTHREAD_RUNNING;
-		this_cpu_inc(rcu_cpu_kthread_loops);
-		local_irq_disable();
-		work = *workp;
-		*workp = 0;
-		local_irq_enable();
-		if (work)
-			rcu_kthread_do_work();
-		local_bh_enable();
-		if (*workp == 0) {
-			trace_rcu_utilization(TPS("End CPU kthread@rcu_wait"));
-			*statusp = RCU_KTHREAD_WAITING;
-			return;
-		}
-	}
-	*statusp = RCU_KTHREAD_YIELDING;
-	trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield"));
-	schedule_timeout_interruptible(2);
-	trace_rcu_utilization(TPS("End CPU kthread@rcu_yield"));
-	*statusp = RCU_KTHREAD_WAITING;
-}
-
-/*
- * Set the per-rcu_node kthread's affinity to cover all CPUs that are
- * served by the rcu_node in question.  The CPU hotplug lock is still
- * held, so the value of rnp->qsmaskinit will be stable.
- *
- * We don't include outgoingcpu in the affinity set, use -1 if there is
- * no outgoing CPU.  If there are no CPUs left in the affinity set,
- * this function allows the kthread to execute on any CPU.
- */
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
-{
-	struct task_struct *t = rnp->boost_kthread_task;
-	unsigned long mask = rnp->qsmaskinit;
-	cpumask_var_t cm;
-	int cpu;
-
-	if (!t)
-		return;
-	if (!zalloc_cpumask_var(&cm, GFP_KERNEL))
-		return;
-	for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
-		if ((mask & 0x1) && cpu != outgoingcpu)
-			cpumask_set_cpu(cpu, cm);
-	if (cpumask_weight(cm) == 0) {
-		cpumask_setall(cm);
-		for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++)
-			cpumask_clear_cpu(cpu, cm);
-		WARN_ON_ONCE(cpumask_weight(cm) == 0);
-	}
-	set_cpus_allowed_ptr(t, cm);
-	free_cpumask_var(cm);
-}
-
-static struct smp_hotplug_thread rcu_cpu_thread_spec = {
-	.store			= &rcu_cpu_kthread_task,
-	.thread_should_run	= rcu_cpu_kthread_should_run,
-	.thread_fn		= rcu_cpu_kthread,
-	.thread_comm		= "rcuc/%u",
-	.setup			= rcu_cpu_kthread_setup,
-	.park			= rcu_cpu_kthread_park,
-};
-
-/*
- * Spawn all kthreads -- called as soon as the scheduler is running.
- */
-static int __init rcu_spawn_kthreads(void)
-{
-	struct rcu_node *rnp;
-	int cpu;
-
-	rcu_scheduler_fully_active = 1;
-	for_each_possible_cpu(cpu)
-		per_cpu(rcu_cpu_has_work, cpu) = 0;
-	BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
-	rnp = rcu_get_root(rcu_state);
-	(void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
-	if (NUM_RCU_NODES > 1) {
-		rcu_for_each_leaf_node(rcu_state, rnp)
-			(void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
-	}
-	return 0;
-}
-early_initcall(rcu_spawn_kthreads);
-
-static void rcu_prepare_kthreads(int cpu)
-{
-	struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
-	struct rcu_node *rnp = rdp->mynode;
-
-	/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
-	if (rcu_scheduler_fully_active)
-		(void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
-}
-
-#else /* #ifdef CONFIG_RCU_BOOST */
-
-static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
-{
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-}
-
-static void invoke_rcu_callbacks_kthread(void)
-{
-	WARN_ON_ONCE(1);
-}
-
-static bool rcu_is_callbacks_kthread(void)
-{
-	return false;
-}
-
-static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
-{
-}
-
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
-{
-}
-
-static int __init rcu_scheduler_really_started(void)
-{
-	rcu_scheduler_fully_active = 1;
-	return 0;
-}
-early_initcall(rcu_scheduler_really_started);
-
-static void rcu_prepare_kthreads(int cpu)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_BOOST */
-
-#if !defined(CONFIG_RCU_FAST_NO_HZ)
-
-/*
- * 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.  This function is part of the RCU implementation; it is -not-
- * an exported member of the RCU API.
- *
- * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs
- * any flavor of RCU.
- */
-int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
-{
-	*delta_jiffies = ULONG_MAX;
-	return rcu_cpu_has_callbacks(cpu, NULL);
-}
-
-/*
- * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up
- * after it.
- */
-static void rcu_cleanup_after_idle(int cpu)
-{
-}
-
-/*
- * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n,
- * is nothing.
- */
-static void rcu_prepare_for_idle(int cpu)
-{
-}
-
-/*
- * Don't bother keeping a running count of the number of RCU callbacks
- * posted because CONFIG_RCU_FAST_NO_HZ=n.
- */
-static void rcu_idle_count_callbacks_posted(void)
-{
-}
-
-#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */
-
-/*
- * This code is invoked when a CPU goes idle, at which point we want
- * to have the CPU do everything required for RCU so that it can enter
- * the energy-efficient dyntick-idle mode.  This is handled by a
- * state machine implemented by rcu_prepare_for_idle() below.
- *
- * The following three proprocessor symbols control this state machine:
- *
- * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted
- *	to sleep in dyntick-idle mode with RCU callbacks pending.  This
- *	is sized to be roughly one RCU grace period.  Those energy-efficiency
- *	benchmarkers who might otherwise be tempted to set this to a large
- *	number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your
- *	system.  And if you are -that- concerned about energy efficiency,
- *	just power the system down and be done with it!
- * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is
- *	permitted to sleep in dyntick-idle mode with only lazy RCU
- *	callbacks pending.  Setting this too high can OOM your system.
- *
- * The values below work well in practice.  If future workloads require
- * adjustment, they can be converted into kernel config parameters, though
- * making the state machine smarter might be a better option.
- */
-#define RCU_IDLE_GP_DELAY 4		/* Roughly one grace period. */
-#define RCU_IDLE_LAZY_GP_DELAY (6 * HZ)	/* Roughly six seconds. */
-
-static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY;
-module_param(rcu_idle_gp_delay, int, 0644);
-static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY;
-module_param(rcu_idle_lazy_gp_delay, int, 0644);
-
-extern int tick_nohz_enabled;
-
-/*
- * Try to advance callbacks for all flavors of RCU on the current CPU, but
- * only if it has been awhile since the last time we did so.  Afterwards,
- * if there are any callbacks ready for immediate invocation, return true.
- */
-static bool rcu_try_advance_all_cbs(void)
-{
-	bool cbs_ready = false;
-	struct rcu_data *rdp;
-	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
-	struct rcu_node *rnp;
-	struct rcu_state *rsp;
-
-	/* Exit early if we advanced recently. */
-	if (jiffies == rdtp->last_advance_all)
-		return 0;
-	rdtp->last_advance_all = jiffies;
-
-	for_each_rcu_flavor(rsp) {
-		rdp = this_cpu_ptr(rsp->rda);
-		rnp = rdp->mynode;
-
-		/*
-		 * Don't bother checking unless a grace period has
-		 * completed since we last checked and there are
-		 * callbacks not yet ready to invoke.
-		 */
-		if (rdp->completed != rnp->completed &&
-		    rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL])
-			note_gp_changes(rsp, rdp);
-
-		if (cpu_has_callbacks_ready_to_invoke(rdp))
-			cbs_ready = true;
-	}
-	return cbs_ready;
-}
-
-/*
- * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready
- * to invoke.  If the CPU has callbacks, try to advance them.  Tell the
- * caller to set the timeout based on whether or not there are non-lazy
- * callbacks.
- *
- * The caller must have disabled interrupts.
- */
-int rcu_needs_cpu(int cpu, unsigned long *dj)
-{
-	struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
-
-	/* Snapshot to detect later posting of non-lazy callback. */
-	rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted;
-
-	/* If no callbacks, RCU doesn't need the CPU. */
-	if (!rcu_cpu_has_callbacks(cpu, &rdtp->all_lazy)) {
-		*dj = ULONG_MAX;
-		return 0;
-	}
-
-	/* Attempt to advance callbacks. */
-	if (rcu_try_advance_all_cbs()) {
-		/* Some ready to invoke, so initiate later invocation. */
-		invoke_rcu_core();
-		return 1;
-	}
-	rdtp->last_accelerate = jiffies;
-
-	/* Request timer delay depending on laziness, and round. */
-	if (!rdtp->all_lazy) {
-		*dj = round_up(rcu_idle_gp_delay + jiffies,
-			       rcu_idle_gp_delay) - jiffies;
-	} else {
-		*dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies;
-	}
-	return 0;
-}
-
-/*
- * Prepare a CPU for idle from an RCU perspective.  The first major task
- * is to sense whether nohz mode has been enabled or disabled via sysfs.
- * The second major task is to check to see if a non-lazy callback has
- * arrived at a CPU that previously had only lazy callbacks.  The third
- * major task is to accelerate (that is, assign grace-period numbers to)
- * any recently arrived callbacks.
- *
- * The caller must have disabled interrupts.
- */
-static void rcu_prepare_for_idle(int cpu)
-{
-	struct rcu_data *rdp;
-	struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
-	struct rcu_node *rnp;
-	struct rcu_state *rsp;
-	int tne;
-
-	/* Handle nohz enablement switches conservatively. */
-	tne = ACCESS_ONCE(tick_nohz_enabled);
-	if (tne != rdtp->tick_nohz_enabled_snap) {
-		if (rcu_cpu_has_callbacks(cpu, NULL))
-			invoke_rcu_core(); /* force nohz to see update. */
-		rdtp->tick_nohz_enabled_snap = tne;
-		return;
-	}
-	if (!tne)
-		return;
-
-	/* If this is a no-CBs CPU, no callbacks, just return. */
-	if (rcu_is_nocb_cpu(cpu))
-		return;
-
-	/*
-	 * If a non-lazy callback arrived at a CPU having only lazy
-	 * callbacks, invoke RCU core for the side-effect of recalculating
-	 * idle duration on re-entry to idle.
-	 */
-	if (rdtp->all_lazy &&
-	    rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) {
-		rdtp->all_lazy = false;
-		rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted;
-		invoke_rcu_core();
-		return;
-	}
-
-	/*
-	 * If we have not yet accelerated this jiffy, accelerate all
-	 * callbacks on this CPU.
-	 */
-	if (rdtp->last_accelerate == jiffies)
-		return;
-	rdtp->last_accelerate = jiffies;
-	for_each_rcu_flavor(rsp) {
-		rdp = per_cpu_ptr(rsp->rda, cpu);
-		if (!*rdp->nxttail[RCU_DONE_TAIL])
-			continue;
-		rnp = rdp->mynode;
-		raw_spin_lock(&rnp->lock); /* irqs already disabled. */
-		rcu_accelerate_cbs(rsp, rnp, rdp);
-		raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
-	}
-}
-
-/*
- * Clean up for exit from idle.  Attempt to advance callbacks based on
- * any grace periods that elapsed while the CPU was idle, and if any
- * callbacks are now ready to invoke, initiate invocation.
- */
-static void rcu_cleanup_after_idle(int cpu)
-{
-
-	if (rcu_is_nocb_cpu(cpu))
-		return;
-	if (rcu_try_advance_all_cbs())
-		invoke_rcu_core();
-}
-
-/*
- * Keep a running count of the number of non-lazy callbacks posted
- * on this CPU.  This running counter (which is never decremented) allows
- * rcu_prepare_for_idle() to detect when something out of the idle loop
- * posts a callback, even if an equal number of callbacks are invoked.
- * Of course, callbacks should only be posted from within a trace event
- * designed to be called from idle or from within RCU_NONIDLE().
- */
-static void rcu_idle_count_callbacks_posted(void)
-{
-	__this_cpu_add(rcu_dynticks.nonlazy_posted, 1);
-}
-
-/*
- * Data for flushing lazy RCU callbacks at OOM time.
- */
-static atomic_t oom_callback_count;
-static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq);
-
-/*
- * RCU OOM callback -- decrement the outstanding count and deliver the
- * wake-up if we are the last one.
- */
-static void rcu_oom_callback(struct rcu_head *rhp)
-{
-	if (atomic_dec_and_test(&oom_callback_count))
-		wake_up(&oom_callback_wq);
-}
-
-/*
- * Post an rcu_oom_notify callback on the current CPU if it has at
- * least one lazy callback.  This will unnecessarily post callbacks
- * to CPUs that already have a non-lazy callback at the end of their
- * callback list, but this is an infrequent operation, so accept some
- * extra overhead to keep things simple.
- */
-static void rcu_oom_notify_cpu(void *unused)
-{
-	struct rcu_state *rsp;
-	struct rcu_data *rdp;
-
-	for_each_rcu_flavor(rsp) {
-		rdp = __this_cpu_ptr(rsp->rda);
-		if (rdp->qlen_lazy != 0) {
-			atomic_inc(&oom_callback_count);
-			rsp->call(&rdp->oom_head, rcu_oom_callback);
-		}
-	}
-}
-
-/*
- * If low on memory, ensure that each CPU has a non-lazy callback.
- * This will wake up CPUs that have only lazy callbacks, in turn
- * ensuring that they free up the corresponding memory in a timely manner.
- * Because an uncertain amount of memory will be freed in some uncertain
- * timeframe, we do not claim to have freed anything.
- */
-static int rcu_oom_notify(struct notifier_block *self,
-			  unsigned long notused, void *nfreed)
-{
-	int cpu;
-
-	/* Wait for callbacks from earlier instance to complete. */
-	wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0);
-
-	/*
-	 * Prevent premature wakeup: ensure that all increments happen
-	 * before there is a chance of the counter reaching zero.
-	 */
-	atomic_set(&oom_callback_count, 1);
-
-	get_online_cpus();
-	for_each_online_cpu(cpu) {
-		smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1);
-		cond_resched();
-	}
-	put_online_cpus();
-
-	/* Unconditionally decrement: no need to wake ourselves up. */
-	atomic_dec(&oom_callback_count);
-
-	return NOTIFY_OK;
-}
-
-static struct notifier_block rcu_oom_nb = {
-	.notifier_call = rcu_oom_notify
-};
-
-static int __init rcu_register_oom_notifier(void)
-{
-	register_oom_notifier(&rcu_oom_nb);
-	return 0;
-}
-early_initcall(rcu_register_oom_notifier);
-
-#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
-
-#ifdef CONFIG_RCU_CPU_STALL_INFO
-
-#ifdef CONFIG_RCU_FAST_NO_HZ
-
-static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
-{
-	struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
-	unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap;
-
-	sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c",
-		rdtp->last_accelerate & 0xffff, jiffies & 0xffff,
-		ulong2long(nlpd),
-		rdtp->all_lazy ? 'L' : '.',
-		rdtp->tick_nohz_enabled_snap ? '.' : 'D');
-}
-
-#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
-
-static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
-{
-	*cp = '\0';
-}
-
-#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */
-
-/* Initiate the stall-info list. */
-static void print_cpu_stall_info_begin(void)
-{
-	pr_cont("\n");
-}
-
-/*
- * Print out diagnostic information for the specified stalled CPU.
- *
- * If the specified CPU is aware of the current RCU grace period
- * (flavor specified by rsp), then print the number of scheduling
- * clock interrupts the CPU has taken during the time that it has
- * been aware.  Otherwise, print the number of RCU grace periods
- * that this CPU is ignorant of, for example, "1" if the CPU was
- * aware of the previous grace period.
- *
- * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info.
- */
-static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
-{
-	char fast_no_hz[72];
-	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
-	struct rcu_dynticks *rdtp = rdp->dynticks;
-	char *ticks_title;
-	unsigned long ticks_value;
-
-	if (rsp->gpnum == rdp->gpnum) {
-		ticks_title = "ticks this GP";
-		ticks_value = rdp->ticks_this_gp;
-	} else {
-		ticks_title = "GPs behind";
-		ticks_value = rsp->gpnum - rdp->gpnum;
-	}
-	print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
-	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,
-	       rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
-	       fast_no_hz);
-}
-
-/* Terminate the stall-info list. */
-static void print_cpu_stall_info_end(void)
-{
-	pr_err("\t");
-}
-
-/* Zero ->ticks_this_gp for all flavors of RCU. */
-static void zero_cpu_stall_ticks(struct rcu_data *rdp)
-{
-	rdp->ticks_this_gp = 0;
-	rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id());
-}
-
-/* Increment ->ticks_this_gp for all flavors of RCU. */
-static void increment_cpu_stall_ticks(void)
-{
-	struct rcu_state *rsp;
-
-	for_each_rcu_flavor(rsp)
-		__this_cpu_ptr(rsp->rda)->ticks_this_gp++;
-}
-
-#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
-
-static void print_cpu_stall_info_begin(void)
-{
-	pr_cont(" {");
-}
-
-static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
-{
-	pr_cont(" %d", cpu);
-}
-
-static void print_cpu_stall_info_end(void)
-{
-	pr_cont("} ");
-}
-
-static void zero_cpu_stall_ticks(struct rcu_data *rdp)
-{
-}
-
-static void increment_cpu_stall_ticks(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */
-
-#ifdef CONFIG_RCU_NOCB_CPU
-
-/*
- * Offload callback processing from the boot-time-specified set of CPUs
- * specified by rcu_nocb_mask.  For each CPU in the set, there is a
- * kthread created that pulls the callbacks from the corresponding CPU,
- * waits for a grace period to elapse, and invokes the callbacks.
- * The no-CBs CPUs do a wake_up() on their kthread when they insert
- * a callback into any empty list, unless the rcu_nocb_poll boot parameter
- * has been specified, in which case each kthread actively polls its
- * CPU.  (Which isn't so great for energy efficiency, but which does
- * reduce RCU's overhead on that CPU.)
- *
- * This is intended to be used in conjunction with Frederic Weisbecker's
- * adaptive-idle work, which would seriously reduce OS jitter on CPUs
- * running CPU-bound user-mode computations.
- *
- * Offloading of callback processing could also in theory be used as
- * an energy-efficiency measure because CPUs with no RCU callbacks
- * queued are more aggressive about entering dyntick-idle mode.
- */
-
-
-/* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */
-static int __init rcu_nocb_setup(char *str)
-{
-	alloc_bootmem_cpumask_var(&rcu_nocb_mask);
-	have_rcu_nocb_mask = true;
-	cpulist_parse(str, rcu_nocb_mask);
-	return 1;
-}
-__setup("rcu_nocbs=", rcu_nocb_setup);
-
-static int __init parse_rcu_nocb_poll(char *arg)
-{
-	rcu_nocb_poll = 1;
-	return 0;
-}
-early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
-
-/*
- * Do any no-CBs CPUs need another grace period?
- *
- * Interrupts must be disabled.  If the caller does not hold the root
- * rnp_node structure's ->lock, the results are advisory only.
- */
-static int rcu_nocb_needs_gp(struct rcu_state *rsp)
-{
-	struct rcu_node *rnp = rcu_get_root(rsp);
-
-	return rnp->need_future_gp[(ACCESS_ONCE(rnp->completed) + 1) & 0x1];
-}
-
-/*
- * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
- * grace period.
- */
-static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
-{
-	wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]);
-}
-
-/*
- * Set the root rcu_node structure's ->need_future_gp field
- * based on the sum of those of all rcu_node structures.  This does
- * double-count the root rcu_node structure's requests, but this
- * is necessary to handle the possibility of a rcu_nocb_kthread()
- * having awakened during the time that the rcu_node structures
- * were being updated for the end of the previous grace period.
- */
-static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
-{
-	rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq;
-}
-
-static void rcu_init_one_nocb(struct rcu_node *rnp)
-{
-	init_waitqueue_head(&rnp->nocb_gp_wq[0]);
-	init_waitqueue_head(&rnp->nocb_gp_wq[1]);
-}
-
-/* Is the specified CPU a no-CPUs CPU? */
-bool rcu_is_nocb_cpu(int cpu)
-{
-	if (have_rcu_nocb_mask)
-		return cpumask_test_cpu(cpu, rcu_nocb_mask);
-	return false;
-}
-
-/*
- * Enqueue the specified string of rcu_head structures onto the specified
- * CPU's no-CBs lists.  The CPU is specified by rdp, the head of the
- * string by rhp, and the tail of the string by rhtp.  The non-lazy/lazy
- * counts are supplied by rhcount and rhcount_lazy.
- *
- * If warranted, also wake up the kthread servicing this CPUs queues.
- */
-static void __call_rcu_nocb_enqueue(struct rcu_data *rdp,
-				    struct rcu_head *rhp,
-				    struct rcu_head **rhtp,
-				    int rhcount, int rhcount_lazy)
-{
-	int len;
-	struct rcu_head **old_rhpp;
-	struct task_struct *t;
-
-	/* Enqueue the callback on the nocb list and update counts. */
-	old_rhpp = xchg(&rdp->nocb_tail, rhtp);
-	ACCESS_ONCE(*old_rhpp) = rhp;
-	atomic_long_add(rhcount, &rdp->nocb_q_count);
-	atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy);
-
-	/* If we are not being polled and there is a kthread, awaken it ... */
-	t = ACCESS_ONCE(rdp->nocb_kthread);
-	if (rcu_nocb_poll || !t) {
-		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
-				    TPS("WakeNotPoll"));
-		return;
-	}
-	len = atomic_long_read(&rdp->nocb_q_count);
-	if (old_rhpp == &rdp->nocb_head) {
-		wake_up(&rdp->nocb_wq); /* ... only if queue was empty ... */
-		rdp->qlen_last_fqs_check = 0;
-		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeEmpty"));
-	} else if (len > rdp->qlen_last_fqs_check + qhimark) {
-		wake_up_process(t); /* ... or if many callbacks queued. */
-		rdp->qlen_last_fqs_check = LONG_MAX / 2;
-		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeOvf"));
-	} else {
-		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot"));
-	}
-	return;
-}
-
-/*
- * This is a helper for __call_rcu(), which invokes this when the normal
- * callback queue is inoperable.  If this is not a no-CBs CPU, this
- * function returns failure back to __call_rcu(), which can complain
- * appropriately.
- *
- * Otherwise, this function queues the callback where the corresponding
- * "rcuo" kthread can find it.
- */
-static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
-			    bool lazy)
-{
-
-	if (!rcu_is_nocb_cpu(rdp->cpu))
-		return 0;
-	__call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy);
-	if (__is_kfree_rcu_offset((unsigned long)rhp->func))
-		trace_rcu_kfree_callback(rdp->rsp->name, rhp,
-					 (unsigned long)rhp->func,
-					 -atomic_long_read(&rdp->nocb_q_count_lazy),
-					 -atomic_long_read(&rdp->nocb_q_count));
-	else
-		trace_rcu_callback(rdp->rsp->name, rhp,
-				   -atomic_long_read(&rdp->nocb_q_count_lazy),
-				   -atomic_long_read(&rdp->nocb_q_count));
-	return 1;
-}
-
-/*
- * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is
- * not a no-CBs CPU.
- */
-static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
-						     struct rcu_data *rdp)
-{
-	long ql = rsp->qlen;
-	long qll = rsp->qlen_lazy;
-
-	/* If this is not a no-CBs CPU, tell the caller to do it the old way. */
-	if (!rcu_is_nocb_cpu(smp_processor_id()))
-		return 0;
-	rsp->qlen = 0;
-	rsp->qlen_lazy = 0;
-
-	/* First, enqueue the donelist, if any.  This preserves CB ordering. */
-	if (rsp->orphan_donelist != NULL) {
-		__call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist,
-					rsp->orphan_donetail, ql, qll);
-		ql = qll = 0;
-		rsp->orphan_donelist = NULL;
-		rsp->orphan_donetail = &rsp->orphan_donelist;
-	}
-	if (rsp->orphan_nxtlist != NULL) {
-		__call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist,
-					rsp->orphan_nxttail, ql, qll);
-		ql = qll = 0;
-		rsp->orphan_nxtlist = NULL;
-		rsp->orphan_nxttail = &rsp->orphan_nxtlist;
-	}
-	return 1;
-}
-
-/*
- * If necessary, kick off a new grace period, and either way wait
- * for a subsequent grace period to complete.
- */
-static void rcu_nocb_wait_gp(struct rcu_data *rdp)
-{
-	unsigned long c;
-	bool d;
-	unsigned long flags;
-	struct rcu_node *rnp = rdp->mynode;
-
-	raw_spin_lock_irqsave(&rnp->lock, flags);
-	c = rcu_start_future_gp(rnp, rdp);
-	raw_spin_unlock_irqrestore(&rnp->lock, flags);
-
-	/*
-	 * Wait for the grace period.  Do so interruptibly to avoid messing
-	 * up the load average.
-	 */
-	trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait"));
-	for (;;) {
-		wait_event_interruptible(
-			rnp->nocb_gp_wq[c & 0x1],
-			(d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c)));
-		if (likely(d))
-			break;
-		flush_signals(current);
-		trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait"));
-	}
-	trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait"));
-	smp_mb(); /* Ensure that CB invocation happens after GP end. */
-}
-
-/*
- * Per-rcu_data kthread, but only for no-CBs CPUs.  Each kthread invokes
- * callbacks queued by the corresponding no-CBs CPU.
- */
-static int rcu_nocb_kthread(void *arg)
-{
-	int c, cl;
-	bool firsttime = 1;
-	struct rcu_head *list;
-	struct rcu_head *next;
-	struct rcu_head **tail;
-	struct rcu_data *rdp = arg;
-
-	/* Each pass through this loop invokes one batch of callbacks */
-	for (;;) {
-		/* If not polling, wait for next batch of callbacks. */
-		if (!rcu_nocb_poll) {
-			trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
-					    TPS("Sleep"));
-			wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head);
-		} else if (firsttime) {
-			firsttime = 0;
-			trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
-					    TPS("Poll"));
-		}
-		list = ACCESS_ONCE(rdp->nocb_head);
-		if (!list) {
-			if (!rcu_nocb_poll)
-				trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
-						    TPS("WokeEmpty"));
-			schedule_timeout_interruptible(1);
-			flush_signals(current);
-			continue;
-		}
-		firsttime = 1;
-		trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
-				    TPS("WokeNonEmpty"));
-
-		/*
-		 * Extract queued callbacks, update counts, and wait
-		 * for a grace period to elapse.
-		 */
-		ACCESS_ONCE(rdp->nocb_head) = NULL;
-		tail = xchg(&rdp->nocb_tail, &rdp->nocb_head);
-		c = atomic_long_xchg(&rdp->nocb_q_count, 0);
-		cl = atomic_long_xchg(&rdp->nocb_q_count_lazy, 0);
-		ACCESS_ONCE(rdp->nocb_p_count) += c;
-		ACCESS_ONCE(rdp->nocb_p_count_lazy) += cl;
-		rcu_nocb_wait_gp(rdp);
-
-		/* Each pass through the following loop invokes a callback. */
-		trace_rcu_batch_start(rdp->rsp->name, cl, c, -1);
-		c = cl = 0;
-		while (list) {
-			next = list->next;
-			/* Wait for enqueuing to complete, if needed. */
-			while (next == NULL && &list->next != tail) {
-				trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
-						    TPS("WaitQueue"));
-				schedule_timeout_interruptible(1);
-				trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
-						    TPS("WokeQueue"));
-				next = list->next;
-			}
-			debug_rcu_head_unqueue(list);
-			local_bh_disable();
-			if (__rcu_reclaim(rdp->rsp->name, list))
-				cl++;
-			c++;
-			local_bh_enable();
-			list = next;
-		}
-		trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1);
-		ACCESS_ONCE(rdp->nocb_p_count) -= c;
-		ACCESS_ONCE(rdp->nocb_p_count_lazy) -= cl;
-		rdp->n_nocbs_invoked += c;
-	}
-	return 0;
-}
-
-/* Initialize per-rcu_data variables for no-CBs CPUs. */
-static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
-{
-	rdp->nocb_tail = &rdp->nocb_head;
-	init_waitqueue_head(&rdp->nocb_wq);
-}
-
-/* Create a kthread for each RCU flavor for each no-CBs CPU. */
-static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp)
-{
-	int cpu;
-	struct rcu_data *rdp;
-	struct task_struct *t;
-
-	if (rcu_nocb_mask == NULL)
-		return;
-	for_each_cpu(cpu, rcu_nocb_mask) {
-		rdp = per_cpu_ptr(rsp->rda, cpu);
-		t = kthread_run(rcu_nocb_kthread, rdp,
-				"rcuo%c/%d", rsp->abbr, cpu);
-		BUG_ON(IS_ERR(t));
-		ACCESS_ONCE(rdp->nocb_kthread) = t;
-	}
-}
-
-/* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */
-static bool init_nocb_callback_list(struct rcu_data *rdp)
-{
-	if (rcu_nocb_mask == NULL ||
-	    !cpumask_test_cpu(rdp->cpu, rcu_nocb_mask))
-		return false;
-	rdp->nxttail[RCU_NEXT_TAIL] = NULL;
-	return true;
-}
-
-#else /* #ifdef CONFIG_RCU_NOCB_CPU */
-
-static int rcu_nocb_needs_gp(struct rcu_state *rsp)
-{
-	return 0;
-}
-
-static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
-{
-}
-
-static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq)
-{
-}
-
-static void rcu_init_one_nocb(struct rcu_node *rnp)
-{
-}
-
-static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
-			    bool lazy)
-{
-	return 0;
-}
-
-static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
-						     struct rcu_data *rdp)
-{
-	return 0;
-}
-
-static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
-{
-}
-
-static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp)
-{
-}
-
-static bool init_nocb_callback_list(struct rcu_data *rdp)
-{
-	return false;
-}
-
-#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
-
-/*
- * An adaptive-ticks CPU can potentially execute in kernel mode for an
- * arbitrarily long period of time with the scheduling-clock tick turned
- * off.  RCU will be paying attention to this CPU because it is in the
- * kernel, but the CPU cannot be guaranteed to be executing the RCU state
- * machine because the scheduling-clock tick has been disabled.  Therefore,
- * if an adaptive-ticks CPU is failing to respond to the current grace
- * period and has not be idle from an RCU perspective, kick it.
- */
-static void rcu_kick_nohz_cpu(int cpu)
-{
-#ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_cpu(cpu))
-		smp_send_reschedule(cpu);
-#endif /* #ifdef CONFIG_NO_HZ_FULL */
-}
-
-
-#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
-
-/*
- * Define RCU flavor that holds sysidle state.  This needs to be the
- * most active flavor of RCU.
- */
-#ifdef CONFIG_PREEMPT_RCU
-static struct rcu_state *rcu_sysidle_state = &rcu_preempt_state;
-#else /* #ifdef CONFIG_PREEMPT_RCU */
-static struct rcu_state *rcu_sysidle_state = &rcu_sched_state;
-#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
-
-static int full_sysidle_state;		/* Current system-idle state. */
-#define RCU_SYSIDLE_NOT		0	/* Some CPU is not idle. */
-#define RCU_SYSIDLE_SHORT	1	/* All CPUs idle for brief period. */
-#define RCU_SYSIDLE_LONG	2	/* All CPUs idle for long enough. */
-#define RCU_SYSIDLE_FULL	3	/* All CPUs idle, ready for sysidle. */
-#define RCU_SYSIDLE_FULL_NOTED	4	/* Actually entered sysidle state. */
-
-/*
- * Invoked to note exit from irq or task transition to idle.  Note that
- * usermode execution does -not- count as idle here!  After all, we want
- * to detect full-system idle states, not RCU quiescent states and grace
- * periods.  The caller must have disabled interrupts.
- */
-static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq)
-{
-	unsigned long j;
-
-	/* Adjust nesting, check for fully idle. */
-	if (irq) {
-		rdtp->dynticks_idle_nesting--;
-		WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0);
-		if (rdtp->dynticks_idle_nesting != 0)
-			return;  /* Still not fully idle. */
-	} else {
-		if ((rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) ==
-		    DYNTICK_TASK_NEST_VALUE) {
-			rdtp->dynticks_idle_nesting = 0;
-		} else {
-			rdtp->dynticks_idle_nesting -= DYNTICK_TASK_NEST_VALUE;
-			WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0);
-			return;  /* Still not fully idle. */
-		}
-	}
-
-	/* Record start of fully idle period. */
-	j = jiffies;
-	ACCESS_ONCE(rdtp->dynticks_idle_jiffies) = j;
-	smp_mb__before_atomic_inc();
-	atomic_inc(&rdtp->dynticks_idle);
-	smp_mb__after_atomic_inc();
-	WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1);
-}
-
-/*
- * Unconditionally force exit from full system-idle state.  This is
- * invoked when a normal CPU exits idle, but must be called separately
- * for the timekeeping CPU (tick_do_timer_cpu).  The reason for this
- * is that the timekeeping CPU is permitted to take scheduling-clock
- * interrupts while the system is in system-idle state, and of course
- * rcu_sysidle_exit() has no way of distinguishing a scheduling-clock
- * interrupt from any other type of interrupt.
- */
-void rcu_sysidle_force_exit(void)
-{
-	int oldstate = ACCESS_ONCE(full_sysidle_state);
-	int newoldstate;
-
-	/*
-	 * Each pass through the following loop attempts to exit full
-	 * system-idle state.  If contention proves to be a problem,
-	 * a trylock-based contention tree could be used here.
-	 */
-	while (oldstate > RCU_SYSIDLE_SHORT) {
-		newoldstate = cmpxchg(&full_sysidle_state,
-				      oldstate, RCU_SYSIDLE_NOT);
-		if (oldstate == newoldstate &&
-		    oldstate == RCU_SYSIDLE_FULL_NOTED) {
-			rcu_kick_nohz_cpu(tick_do_timer_cpu);
-			return; /* We cleared it, done! */
-		}
-		oldstate = newoldstate;
-	}
-	smp_mb(); /* Order initial oldstate fetch vs. later non-idle work. */
-}
-
-/*
- * Invoked to note entry to irq or task transition from idle.  Note that
- * usermode execution does -not- count as idle here!  The caller must
- * have disabled interrupts.
- */
-static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq)
-{
-	/* Adjust nesting, check for already non-idle. */
-	if (irq) {
-		rdtp->dynticks_idle_nesting++;
-		WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0);
-		if (rdtp->dynticks_idle_nesting != 1)
-			return; /* Already non-idle. */
-	} else {
-		/*
-		 * Allow for irq misnesting.  Yes, it really is possible
-		 * to enter an irq handler then never leave it, and maybe
-		 * also vice versa.  Handle both possibilities.
-		 */
-		if (rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) {
-			rdtp->dynticks_idle_nesting += DYNTICK_TASK_NEST_VALUE;
-			WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0);
-			return; /* Already non-idle. */
-		} else {
-			rdtp->dynticks_idle_nesting = DYNTICK_TASK_EXIT_IDLE;
-		}
-	}
-
-	/* Record end of idle period. */
-	smp_mb__before_atomic_inc();
-	atomic_inc(&rdtp->dynticks_idle);
-	smp_mb__after_atomic_inc();
-	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1));
-
-	/*
-	 * If we are the timekeeping CPU, we are permitted to be non-idle
-	 * during a system-idle state.  This must be the case, because
-	 * the timekeeping CPU has to take scheduling-clock interrupts
-	 * during the time that the system is transitioning to full
-	 * system-idle state.  This means that the timekeeping CPU must
-	 * invoke rcu_sysidle_force_exit() directly if it does anything
-	 * more than take a scheduling-clock interrupt.
-	 */
-	if (smp_processor_id() == tick_do_timer_cpu)
-		return;
-
-	/* Update system-idle state: We are clearly no longer fully idle! */
-	rcu_sysidle_force_exit();
-}
-
-/*
- * Check to see if the current CPU is idle.  Note that usermode execution
- * does not count as idle.  The caller must have disabled interrupts.
- */
-static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
-				  unsigned long *maxj)
-{
-	int cur;
-	unsigned long j;
-	struct rcu_dynticks *rdtp = rdp->dynticks;
-
-	/*
-	 * If some other CPU has already reported non-idle, if this is
-	 * not the flavor of RCU that tracks sysidle state, or if this
-	 * is an offline or the timekeeping CPU, nothing to do.
-	 */
-	if (!*isidle || rdp->rsp != rcu_sysidle_state ||
-	    cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu)
-		return;
-	if (rcu_gp_in_progress(rdp->rsp))
-		WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu);
-
-	/* Pick up current idle and NMI-nesting counter and check. */
-	cur = atomic_read(&rdtp->dynticks_idle);
-	if (cur & 0x1) {
-		*isidle = false; /* We are not idle! */
-		return;
-	}
-	smp_mb(); /* Read counters before timestamps. */
-
-	/* Pick up timestamps. */
-	j = ACCESS_ONCE(rdtp->dynticks_idle_jiffies);
-	/* If this CPU entered idle more recently, update maxj timestamp. */
-	if (ULONG_CMP_LT(*maxj, j))
-		*maxj = j;
-}
-
-/*
- * Is this the flavor of RCU that is handling full-system idle?
- */
-static bool is_sysidle_rcu_state(struct rcu_state *rsp)
-{
-	return rsp == rcu_sysidle_state;
-}
-
-/*
- * Bind the grace-period kthread for the sysidle flavor of RCU to the
- * timekeeping CPU.
- */
-static void rcu_bind_gp_kthread(void)
-{
-	int cpu = ACCESS_ONCE(tick_do_timer_cpu);
-
-	if (cpu < 0 || cpu >= nr_cpu_ids)
-		return;
-	if (raw_smp_processor_id() != cpu)
-		set_cpus_allowed_ptr(current, cpumask_of(cpu));
-}
-
-/*
- * Return a delay in jiffies based on the number of CPUs, rcu_node
- * leaf fanout, and jiffies tick rate.  The idea is to allow larger
- * systems more time to transition to full-idle state in order to
- * avoid the cache thrashing that otherwise occur on the state variable.
- * Really small systems (less than a couple of tens of CPUs) should
- * instead use a single global atomically incremented counter, and later
- * versions of this will automatically reconfigure themselves accordingly.
- */
-static unsigned long rcu_sysidle_delay(void)
-{
-	if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL)
-		return 0;
-	return DIV_ROUND_UP(nr_cpu_ids * HZ, rcu_fanout_leaf * 1000);
-}
-
-/*
- * Advance the full-system-idle state.  This is invoked when all of
- * the non-timekeeping CPUs are idle.
- */
-static void rcu_sysidle(unsigned long j)
-{
-	/* Check the current state. */
-	switch (ACCESS_ONCE(full_sysidle_state)) {
-	case RCU_SYSIDLE_NOT:
-
-		/* First time all are idle, so note a short idle period. */
-		ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_SHORT;
-		break;
-
-	case RCU_SYSIDLE_SHORT:
-
-		/*
-		 * Idle for a bit, time to advance to next state?
-		 * cmpxchg failure means race with non-idle, let them win.
-		 */
-		if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay()))
-			(void)cmpxchg(&full_sysidle_state,
-				      RCU_SYSIDLE_SHORT, RCU_SYSIDLE_LONG);
-		break;
-
-	case RCU_SYSIDLE_LONG:
-
-		/*
-		 * Do an additional check pass before advancing to full.
-		 * cmpxchg failure means race with non-idle, let them win.
-		 */
-		if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay()))
-			(void)cmpxchg(&full_sysidle_state,
-				      RCU_SYSIDLE_LONG, RCU_SYSIDLE_FULL);
-		break;
-
-	default:
-		break;
-	}
-}
-
-/*
- * Found a non-idle non-timekeeping CPU, so kick the system-idle state
- * back to the beginning.
- */
-static void rcu_sysidle_cancel(void)
-{
-	smp_mb();
-	ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT;
-}
-
-/*
- * Update the sysidle state based on the results of a force-quiescent-state
- * scan of the CPUs' dyntick-idle state.
- */
-static void rcu_sysidle_report(struct rcu_state *rsp, int isidle,
-			       unsigned long maxj, bool gpkt)
-{
-	if (rsp != rcu_sysidle_state)
-		return;  /* Wrong flavor, ignore. */
-	if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL)
-		return;  /* Running state machine from timekeeping CPU. */
-	if (isidle)
-		rcu_sysidle(maxj);    /* More idle! */
-	else
-		rcu_sysidle_cancel(); /* Idle is over. */
-}
-
-/*
- * Wrapper for rcu_sysidle_report() when called from the grace-period
- * kthread's context.
- */
-static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
-				  unsigned long maxj)
-{
-	rcu_sysidle_report(rsp, isidle, maxj, true);
-}
-
-/* Callback and function for forcing an RCU grace period. */
-struct rcu_sysidle_head {
-	struct rcu_head rh;
-	int inuse;
-};
-
-static void rcu_sysidle_cb(struct rcu_head *rhp)
-{
-	struct rcu_sysidle_head *rshp;
-
-	/*
-	 * The following memory barrier is needed to replace the
-	 * memory barriers that would normally be in the memory
-	 * allocator.
-	 */
-	smp_mb();  /* grace period precedes setting inuse. */
-
-	rshp = container_of(rhp, struct rcu_sysidle_head, rh);
-	ACCESS_ONCE(rshp->inuse) = 0;
-}
-
-/*
- * Check to see if the system is fully idle, other than the timekeeping CPU.
- * The caller must have disabled interrupts.
- */
-bool rcu_sys_is_idle(void)
-{
-	static struct rcu_sysidle_head rsh;
-	int rss = ACCESS_ONCE(full_sysidle_state);
-
-	if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu))
-		return false;
-
-	/* Handle small-system case by doing a full scan of CPUs. */
-	if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) {
-		int oldrss = rss - 1;
-
-		/*
-		 * One pass to advance to each state up to _FULL.
-		 * Give up if any pass fails to advance the state.
-		 */
-		while (rss < RCU_SYSIDLE_FULL && oldrss < rss) {
-			int cpu;
-			bool isidle = true;
-			unsigned long maxj = jiffies - ULONG_MAX / 4;
-			struct rcu_data *rdp;
-
-			/* Scan all the CPUs looking for nonidle CPUs. */
-			for_each_possible_cpu(cpu) {
-				rdp = per_cpu_ptr(rcu_sysidle_state->rda, cpu);
-				rcu_sysidle_check_cpu(rdp, &isidle, &maxj);
-				if (!isidle)
-					break;
-			}
-			rcu_sysidle_report(rcu_sysidle_state,
-					   isidle, maxj, false);
-			oldrss = rss;
-			rss = ACCESS_ONCE(full_sysidle_state);
-		}
-	}
-
-	/* If this is the first observation of an idle period, record it. */
-	if (rss == RCU_SYSIDLE_FULL) {
-		rss = cmpxchg(&full_sysidle_state,
-			      RCU_SYSIDLE_FULL, RCU_SYSIDLE_FULL_NOTED);
-		return rss == RCU_SYSIDLE_FULL;
-	}
-
-	smp_mb(); /* ensure rss load happens before later caller actions. */
-
-	/* If already fully idle, tell the caller (in case of races). */
-	if (rss == RCU_SYSIDLE_FULL_NOTED)
-		return true;
-
-	/*
-	 * If we aren't there yet, and a grace period is not in flight,
-	 * initiate a grace period.  Either way, tell the caller that
-	 * we are not there yet.  We use an xchg() rather than an assignment
-	 * to make up for the memory barriers that would otherwise be
-	 * provided by the memory allocator.
-	 */
-	if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL &&
-	    !rcu_gp_in_progress(rcu_sysidle_state) &&
-	    !rsh.inuse && xchg(&rsh.inuse, 1) == 0)
-		call_rcu(&rsh.rh, rcu_sysidle_cb);
-	return false;
-}
-
-/*
- * Initialize dynticks sysidle state for CPUs coming online.
- */
-static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp)
-{
-	rdtp->dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE;
-}
-
-#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
-
-static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq)
-{
-}
-
-static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq)
-{
-}
-
-static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
-				  unsigned long *maxj)
-{
-}
-
-static bool is_sysidle_rcu_state(struct rcu_state *rsp)
-{
-	return false;
-}
-
-static void rcu_bind_gp_kthread(void)
-{
-}
-
-static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
-				  unsigned long maxj)
-{
-}
-
-static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp)
-{
-}
-
-#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */