Merge branch 'core/rcu' into core/rcu-for-linus

1 files changed, 371 insertions, 47 deletions

diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index 9bf445664457..6f62b77d93c4 100644
--- a/kernel/rcupreempt.c
+++ b/kernel/rcupreempt.c
@@ -46,11 +46,11 @@
 #include <asm/atomic.h>
 #include <linux/bitops.h>
 #include <linux/module.h>
+#include <linux/kthread.h>
 #include <linux/completion.h>
 #include <linux/moduleparam.h>
 #include <linux/percpu.h>
 #include <linux/notifier.h>
-#include <linux/rcupdate.h>
 #include <linux/cpu.h>
 #include <linux/random.h>
 #include <linux/delay.h>
@@ -82,14 +82,18 @@ struct rcu_data {
         spinlock_t      lock;           /* Protect rcu_data fields. */
         long            completed;      /* Number of last completed batch. */
         int             waitlistcount;
-        struct tasklet_struct rcu_tasklet;
         struct rcu_head *nextlist;
         struct rcu_head **nexttail;
         struct rcu_head *waitlist[GP_STAGES];
         struct rcu_head **waittail[GP_STAGES];
-        struct rcu_head *donelist;
+        struct rcu_head *donelist;      /* from waitlist & waitschedlist */
         struct rcu_head **donetail;
         long rcu_flipctr[2];
+        struct rcu_head *nextschedlist;
+        struct rcu_head **nextschedtail;
+        struct rcu_head *waitschedlist;
+        struct rcu_head **waitschedtail;
+        int rcu_sched_sleeping;
 #ifdef CONFIG_RCU_TRACE
         struct rcupreempt_trace trace;
 #endif /* #ifdef CONFIG_RCU_TRACE */
@@ -131,11 +135,24 @@ enum rcu_try_flip_states {
         rcu_try_flip_waitmb_state,
 };
 
+/*
+ * States for rcu_ctrlblk.rcu_sched_sleep.
+ */
+
+enum rcu_sched_sleep_states {
+        rcu_sched_not_sleeping, /* Not sleeping, callbacks need GP.  */
+        rcu_sched_sleep_prep,   /* Thinking of sleeping, rechecking. */
+        rcu_sched_sleeping,     /* Sleeping, awaken if GP needed. */
+};
+
 struct rcu_ctrlblk {
         spinlock_t      fliplock;       /* Protect state-machine transitions. */
         long            completed;      /* Number of last completed batch. */
         enum rcu_try_flip_states rcu_try_flip_state; /* The current state of
                                                         the rcu state machine */
+        spinlock_t      schedlock;      /* Protect rcu_sched sleep state. */
+        enum rcu_sched_sleep_states sched_sleep; /* rcu_sched state. */
+        wait_queue_head_t sched_wq;     /* Place for rcu_sched to sleep. */
 };
 
 static DEFINE_PER_CPU(struct rcu_data, rcu_data);
@@ -143,8 +160,12 @@ static struct rcu_ctrlblk rcu_ctrlblk = {
         .fliplock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.fliplock),
         .completed = 0,
         .rcu_try_flip_state = rcu_try_flip_idle_state,
+        .schedlock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.schedlock),
+        .sched_sleep = rcu_sched_not_sleeping,
+        .sched_wq = __WAIT_QUEUE_HEAD_INITIALIZER(rcu_ctrlblk.sched_wq),
 };
 
+static struct task_struct *rcu_sched_grace_period_task;
 
 #ifdef CONFIG_RCU_TRACE
 static char *rcu_try_flip_state_names[] =
@@ -207,6 +228,8 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(enum rcu_mb_flag_values, rcu_mb_flag)
  */
 #define RCU_TRACE_RDP(f, rdp) RCU_TRACE(f, &((rdp)->trace));
 
+#define RCU_SCHED_BATCH_TIME (HZ / 50)
+
 /*
  * Return the number of RCU batches processed thus far.  Useful
  * for debug and statistics.
@@ -411,32 +434,34 @@ static void __rcu_advance_callbacks(struct rcu_data *rdp)
         }
 }
 
-#ifdef CONFIG_NO_HZ
+DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_dyntick_sched, rcu_dyntick_sched) = {
+        .dynticks = 1,
+};
 
-DEFINE_PER_CPU(long, dynticks_progress_counter) = 1;
-static DEFINE_PER_CPU(long, rcu_dyntick_snapshot);
+#ifdef CONFIG_NO_HZ
 static DEFINE_PER_CPU(int, rcu_update_flag);
 
 /**
  * rcu_irq_enter - Called from Hard irq handlers and NMI/SMI.
  *
  * If the CPU was idle with dynamic ticks active, this updates the
- * dynticks_progress_counter to let the RCU handling know that the
+ * rcu_dyntick_sched.dynticks to let the RCU handling know that the
  * CPU is active.
  */
 void rcu_irq_enter(void)
 {
         int cpu = smp_processor_id();
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
 
         if (per_cpu(rcu_update_flag, cpu))
                 per_cpu(rcu_update_flag, cpu)++;
 
         /*
          * Only update if we are coming from a stopped ticks mode
-         * (dynticks_progress_counter is even).
+         * (rcu_dyntick_sched.dynticks is even).
          */
         if (!in_interrupt() &&
-            (per_cpu(dynticks_progress_counter, cpu) & 0x1) == 0) {
+            (rdssp->dynticks & 0x1) == 0) {
                 /*
                  * The following might seem like we could have a race
                  * with NMI/SMIs. But this really isn't a problem.
@@ -459,12 +484,12 @@ void rcu_irq_enter(void)
                  * RCU read-side critical sections on this CPU would
                  * have already completed.
                  */
-                per_cpu(dynticks_progress_counter, cpu)++;
+                rdssp->dynticks++;
                 /*
                  * The following memory barrier ensures that any
                  * rcu_read_lock() primitives in the irq handler
                  * are seen by other CPUs to follow the above
-                 * increment to dynticks_progress_counter. This is
+                 * increment to rcu_dyntick_sched.dynticks. This is
                  * required in order for other CPUs to correctly
                  * determine when it is safe to advance the RCU
                  * grace-period state machine.
@@ -472,7 +497,7 @@ void rcu_irq_enter(void)
                 smp_mb(); /* see above block comment. */
                 /*
                  * Since we can't determine the dynamic tick mode from
-                 * the dynticks_progress_counter after this routine,
+                 * the rcu_dyntick_sched.dynticks after this routine,
                  * we use a second flag to acknowledge that we came
                  * from an idle state with ticks stopped.
                  */
@@ -480,7 +505,7 @@ void rcu_irq_enter(void)
                 /*
                  * If we take an NMI/SMI now, they will also increment
                  * the rcu_update_flag, and will not update the
-                 * dynticks_progress_counter on exit. That is for
+                 * rcu_dyntick_sched.dynticks on exit. That is for
                  * this IRQ to do.
                  */
         }
@@ -490,12 +515,13 @@ void rcu_irq_enter(void)
  * rcu_irq_exit - Called from exiting Hard irq context.
  *
  * If the CPU was idle with dynamic ticks active, update the
- * dynticks_progress_counter to put let the RCU handling be
+ * rcu_dyntick_sched.dynticks to put let the RCU handling be
  * aware that the CPU is going back to idle with no ticks.
  */
 void rcu_irq_exit(void)
 {
         int cpu = smp_processor_id();
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
 
         /*
          * rcu_update_flag is set if we interrupted the CPU
@@ -503,7 +529,7 @@ void rcu_irq_exit(void)
          * Once this occurs, we keep track of interrupt nesting
          * because a NMI/SMI could also come in, and we still
          * only want the IRQ that started the increment of the
-         * dynticks_progress_counter to be the one that modifies
+         * rcu_dyntick_sched.dynticks to be the one that modifies
          * it on exit.
          */
         if (per_cpu(rcu_update_flag, cpu)) {
@@ -515,28 +541,29 @@ void rcu_irq_exit(void)
 
                 /*
                  * If an NMI/SMI happens now we are still
-                 * protected by the dynticks_progress_counter being odd.
+                 * protected by the rcu_dyntick_sched.dynticks being odd.
                  */
 
                 /*
                  * The following memory barrier ensures that any
                  * rcu_read_unlock() primitives in the irq handler
                  * are seen by other CPUs to preceed the following
-                 * increment to dynticks_progress_counter. This
+                 * increment to rcu_dyntick_sched.dynticks. This
                  * is required in order for other CPUs to determine
                  * when it is safe to advance the RCU grace-period
                  * state machine.
                  */
                 smp_mb(); /* see above block comment. */
-                per_cpu(dynticks_progress_counter, cpu)++;
-                WARN_ON(per_cpu(dynticks_progress_counter, cpu) & 0x1);
+                rdssp->dynticks++;
+                WARN_ON(rdssp->dynticks & 0x1);
         }
 }
 
 static void dyntick_save_progress_counter(int cpu)
 {
-        per_cpu(rcu_dyntick_snapshot, cpu) =
-                per_cpu(dynticks_progress_counter, cpu);
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+        rdssp->dynticks_snap = rdssp->dynticks;
 }
 
 static inline int
@@ -544,9 +571,10 @@ rcu_try_flip_waitack_needed(int cpu)
 {
         long curr;
         long snap;
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
 
-        curr = per_cpu(dynticks_progress_counter, cpu);
-        snap = per_cpu(rcu_dyntick_snapshot, cpu);
+        curr = rdssp->dynticks;
+        snap = rdssp->dynticks_snap;
         smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
 
         /*
@@ -567,7 +595,7 @@ rcu_try_flip_waitack_needed(int cpu)
          * that this CPU already acknowledged the counter.
          */
 
-        if ((curr - snap) > 2 || (snap & 0x1) == 0)
+        if ((curr - snap) > 2 || (curr & 0x1) == 0)
                 return 0;
 
         /* We need this CPU to explicitly acknowledge the counter flip. */
@@ -580,9 +608,10 @@ rcu_try_flip_waitmb_needed(int cpu)
 {
         long curr;
         long snap;
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
 
-        curr = per_cpu(dynticks_progress_counter, cpu);
-        snap = per_cpu(rcu_dyntick_snapshot, cpu);
+        curr = rdssp->dynticks;
+        snap = rdssp->dynticks_snap;
         smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
 
         /*
@@ -609,14 +638,86 @@ rcu_try_flip_waitmb_needed(int cpu)
         return 1;
 }
 
+static void dyntick_save_progress_counter_sched(int cpu)
+{
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+        rdssp->sched_dynticks_snap = rdssp->dynticks;
+}
+
+static int rcu_qsctr_inc_needed_dyntick(int cpu)
+{
+        long curr;
+        long snap;
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+        curr = rdssp->dynticks;
+        snap = rdssp->sched_dynticks_snap;
+        smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
+
+        /*
+         * If the CPU remained in dynticks mode for the entire time
+         * and didn't take any interrupts, NMIs, SMIs, or whatever,
+         * then it cannot be in the middle of an rcu_read_lock(), so
+         * the next rcu_read_lock() it executes must use the new value
+         * of the counter.  Therefore, this CPU has been in a quiescent
+         * state the entire time, and we don't need to wait for it.
+         */
+
+        if ((curr == snap) && ((curr & 0x1) == 0))
+                return 0;
+
+        /*
+         * If the CPU passed through or entered a dynticks idle phase with
+         * no active irq handlers, then, as above, this CPU has already
+         * passed through a quiescent state.
+         */
+
+        if ((curr - snap) > 2 || (snap & 0x1) == 0)
+                return 0;
+
+        /* We need this CPU to go through a quiescent state. */
+
+        return 1;
+}
+
 #else /* !CONFIG_NO_HZ */
 
-# define dyntick_save_progress_counter(cpu)     do { } while (0)
-# define rcu_try_flip_waitack_needed(cpu)       (1)
-# define rcu_try_flip_waitmb_needed(cpu)        (1)
+# define dyntick_save_progress_counter(cpu)             do { } while (0)
+# define rcu_try_flip_waitack_needed(cpu)               (1)
+# define rcu_try_flip_waitmb_needed(cpu)                (1)
+
+# define dyntick_save_progress_counter_sched(cpu)       do { } while (0)
+# define rcu_qsctr_inc_needed_dyntick(cpu)              (1)
 
 #endif /* CONFIG_NO_HZ */
 
+static void save_qsctr_sched(int cpu)
+{
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+        rdssp->sched_qs_snap = rdssp->sched_qs;
+}
+
+static inline int rcu_qsctr_inc_needed(int cpu)
+{
+        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
+
+        /*
+         * If there has been a quiescent state, no more need to wait
+         * on this CPU.
+         */
+
+        if (rdssp->sched_qs != rdssp->sched_qs_snap) {
+                smp_mb(); /* force ordering with cpu entering schedule(). */
+                return 0;
+        }
+
+        /* We need this CPU to go through a quiescent state. */
+
+        return 1;
+}
+
 /*
  * Get here when RCU is idle.  Decide whether we need to
  * move out of idle state, and return non-zero if so.
@@ -819,6 +920,26 @@ void rcu_check_callbacks(int cpu, int user)
         unsigned long flags;
         struct rcu_data *rdp = RCU_DATA_CPU(cpu);
 
+        /*
+         * If this CPU took its interrupt from user mode or from the
+         * idle loop, and this is not a nested interrupt, then
+         * this CPU has to have exited all prior preept-disable
+         * sections of code.  So increment the counter to note this.
+         *
+         * The memory barrier is needed to handle the case where
+         * writes from a preempt-disable section of code get reordered
+         * into schedule() by this CPU's write buffer.  So the memory
+         * barrier makes sure that the rcu_qsctr_inc() is seen by other
+         * CPUs to happen after any such write.
+         */
+
+        if (user ||
+            (idle_cpu(cpu) && !in_softirq() &&
+             hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+                smp_mb();       /* Guard against aggressive schedule(). */
+                rcu_qsctr_inc(cpu);
+        }
+
         rcu_check_mb(cpu);
         if (rcu_ctrlblk.completed == rdp->completed)
                 rcu_try_flip();
@@ -869,6 +990,8 @@ void rcu_offline_cpu(int cpu)
         struct rcu_head *list = NULL;
         unsigned long flags;
         struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+        struct rcu_head *schedlist = NULL;
+        struct rcu_head **schedtail = &schedlist;
         struct rcu_head **tail = &list;
 
         /*
@@ -882,6 +1005,11 @@ void rcu_offline_cpu(int cpu)
                 rcu_offline_cpu_enqueue(rdp->waitlist[i], rdp->waittail[i],
                                                 list, tail);
         rcu_offline_cpu_enqueue(rdp->nextlist, rdp->nexttail, list, tail);
+        rcu_offline_cpu_enqueue(rdp->waitschedlist, rdp->waitschedtail,
+                                schedlist, schedtail);
+        rcu_offline_cpu_enqueue(rdp->nextschedlist, rdp->nextschedtail,
+                                schedlist, schedtail);
+        rdp->rcu_sched_sleeping = 0;
         spin_unlock_irqrestore(&rdp->lock, flags);
         rdp->waitlistcount = 0;
 
@@ -916,12 +1044,15 @@ void rcu_offline_cpu(int cpu)
          * fix.
          */
 
-        local_irq_save(flags);
+        local_irq_save(flags);  /* disable preempt till we know what lock. */
         rdp = RCU_DATA_ME();
         spin_lock(&rdp->lock);
         *rdp->nexttail = list;
         if (list)
                 rdp->nexttail = tail;
+        *rdp->nextschedtail = schedlist;
+        if (schedlist)
+                rdp->nextschedtail = schedtail;
         spin_unlock_irqrestore(&rdp->lock, flags);
 }
 
@@ -936,10 +1067,25 @@ void rcu_offline_cpu(int cpu)
 void __cpuinit rcu_online_cpu(int cpu)
 {
         unsigned long flags;
+        struct rcu_data *rdp;
 
         spin_lock_irqsave(&rcu_ctrlblk.fliplock, flags);
         cpu_set(cpu, rcu_cpu_online_map);
         spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, flags);
+
+        /*
+         * The rcu_sched grace-period processing might have bypassed
+         * this CPU, given that it was not in the rcu_cpu_online_map
+         * when the grace-period scan started.  This means that the
+         * grace-period task might sleep.  So make sure that if this
+         * should happen, the first callback posted to this CPU will
+         * wake up the grace-period task if need be.
+         */
+
+        rdp = RCU_DATA_CPU(cpu);
+        spin_lock_irqsave(&rdp->lock, flags);
+        rdp->rcu_sched_sleeping = 1;
+        spin_unlock_irqrestore(&rdp->lock, flags);
 }
 
 static void rcu_process_callbacks(struct softirq_action *unused)
@@ -982,31 +1128,196 @@ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
         *rdp->nexttail = head;
         rdp->nexttail = &head->next;
         RCU_TRACE_RDP(rcupreempt_trace_next_add, rdp);
-        spin_unlock(&rdp->lock);
-        local_irq_restore(flags);
+        spin_unlock_irqrestore(&rdp->lock, flags);
 }
 EXPORT_SYMBOL_GPL(call_rcu);
 
+void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+        unsigned long flags;
+        struct rcu_data *rdp;
+        int wake_gp = 0;
+
+        head->func = func;
+        head->next = NULL;
+        local_irq_save(flags);
+        rdp = RCU_DATA_ME();
+        spin_lock(&rdp->lock);
+        *rdp->nextschedtail = head;
+        rdp->nextschedtail = &head->next;
+        if (rdp->rcu_sched_sleeping) {
+
+                /* Grace-period processing might be sleeping... */
+
+                rdp->rcu_sched_sleeping = 0;
+                wake_gp = 1;
+        }
+        spin_unlock_irqrestore(&rdp->lock, flags);
+        if (wake_gp) {
+
+                /* Wake up grace-period processing, unless someone beat us. */
+
+                spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags);
+                if (rcu_ctrlblk.sched_sleep != rcu_sched_sleeping)
+                        wake_gp = 0;
+                rcu_ctrlblk.sched_sleep = rcu_sched_not_sleeping;
+                spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
+                if (wake_gp)
+                        wake_up_interruptible(&rcu_ctrlblk.sched_wq);
+        }
+}
+EXPORT_SYMBOL_GPL(call_rcu_sched);
+
 /*
  * Wait until all currently running preempt_disable() code segments
  * (including hardware-irq-disable segments) complete.  Note that
  * in -rt this does -not- necessarily result in all currently executing
  * interrupt -handlers- having completed.
  */
-void __synchronize_sched(void)
+synchronize_rcu_xxx(__synchronize_sched, call_rcu_sched)
+EXPORT_SYMBOL_GPL(__synchronize_sched);
+
+/*
+ * kthread function that manages call_rcu_sched grace periods.
+ */
+static int rcu_sched_grace_period(void *arg)
 {
-        cpumask_t oldmask;
+        int couldsleep;         /* might sleep after current pass. */
+        int couldsleepnext = 0; /* might sleep after next pass. */
         int cpu;
+        unsigned long flags;
+        struct rcu_data *rdp;
+        int ret;
 
-        if (sched_getaffinity(0, &oldmask) < 0)
-                oldmask = cpu_possible_map;
-        for_each_online_cpu(cpu) {
-                sched_setaffinity(0, &cpumask_of_cpu(cpu));
-                schedule();
-        }
-        sched_setaffinity(0, &oldmask);
+        /*
+         * Each pass through the following loop handles one
+         * rcu_sched grace period cycle.
+         */
+        do {
+                /* Save each CPU's current state. */
+
+                for_each_online_cpu(cpu) {
+                        dyntick_save_progress_counter_sched(cpu);
+                        save_qsctr_sched(cpu);
+                }
+
+                /*
+                 * Sleep for about an RCU grace-period's worth to
+                 * allow better batching and to consume less CPU.
+                 */
+                schedule_timeout_interruptible(RCU_SCHED_BATCH_TIME);
+
+                /*
+                 * If there was nothing to do last time, prepare to
+                 * sleep at the end of the current grace period cycle.
+                 */
+                couldsleep = couldsleepnext;
+                couldsleepnext = 1;
+                if (couldsleep) {
+                        spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags);
+                        rcu_ctrlblk.sched_sleep = rcu_sched_sleep_prep;
+                        spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
+                }
+
+                /*
+                 * Wait on each CPU in turn to have either visited
+                 * a quiescent state or been in dynticks-idle mode.
+                 */
+                for_each_online_cpu(cpu) {
+                        while (rcu_qsctr_inc_needed(cpu) &&
+                               rcu_qsctr_inc_needed_dyntick(cpu)) {
+                                /* resched_cpu(cpu); @@@ */
+                                schedule_timeout_interruptible(1);
+                        }
+                }
+
+                /* Advance callbacks for each CPU.  */
+
+                for_each_online_cpu(cpu) {
+
+                        rdp = RCU_DATA_CPU(cpu);
+                        spin_lock_irqsave(&rdp->lock, flags);
+
+                        /*
+                         * We are running on this CPU irq-disabled, so no
+                         * CPU can go offline until we re-enable irqs.
+                         * The current CPU might have already gone
+                         * offline (between the for_each_offline_cpu and
+                         * the spin_lock_irqsave), but in that case all its
+                         * callback lists will be empty, so no harm done.
+                         *
+                         * Advance the callbacks!  We share normal RCU's
+                         * donelist, since callbacks are invoked the
+                         * same way in either case.
+                         */
+                        if (rdp->waitschedlist != NULL) {
+                                *rdp->donetail = rdp->waitschedlist;
+                                rdp->donetail = rdp->waitschedtail;
+
+                                /*
+                                 * Next rcu_check_callbacks() will
+                                 * do the required raise_softirq().
+                                 */
+                        }
+                        if (rdp->nextschedlist != NULL) {
+                                rdp->waitschedlist = rdp->nextschedlist;
+                                rdp->waitschedtail = rdp->nextschedtail;
+                                couldsleep = 0;
+                                couldsleepnext = 0;
+                        } else {
+                                rdp->waitschedlist = NULL;
+                                rdp->waitschedtail = &rdp->waitschedlist;
+                        }
+                        rdp->nextschedlist = NULL;
+                        rdp->nextschedtail = &rdp->nextschedlist;
+
+                        /* Mark sleep intention. */
+
+                        rdp->rcu_sched_sleeping = couldsleep;
+
+                        spin_unlock_irqrestore(&rdp->lock, flags);
+                }
+
+                /* If we saw callbacks on the last scan, go deal with them. */
+
+                if (!couldsleep)
+                        continue;
+
+                /* Attempt to block... */
+
+                spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags);
+                if (rcu_ctrlblk.sched_sleep != rcu_sched_sleep_prep) {
+
+                        /*
+                         * Someone posted a callback after we scanned.
+                         * Go take care of it.
+                         */
+                        spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
+                        couldsleepnext = 0;
+                        continue;
+                }
+
+                /* Block until the next person posts a callback. */
+
+                rcu_ctrlblk.sched_sleep = rcu_sched_sleeping;
+                spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags);
+                ret = 0;
+                __wait_event_interruptible(rcu_ctrlblk.sched_wq,
+                        rcu_ctrlblk.sched_sleep != rcu_sched_sleeping,
+                        ret);
+
+                /*
+                 * Signals would prevent us from sleeping, and we cannot
+                 * do much with them in any case.  So flush them.
+                 */
+                if (ret)
+                        flush_signals(current);
+                couldsleepnext = 0;
+
+        } while (!kthread_should_stop());
+
+        return (0);
 }
-EXPORT_SYMBOL_GPL(__synchronize_sched);
 
 /*
  * Check to see if any future RCU-related work will need to be done
@@ -1023,7 +1334,9 @@ int rcu_needs_cpu(int cpu)
 
         return (rdp->donelist != NULL ||
                 !!rdp->waitlistcount ||
-                rdp->nextlist != NULL);
+                rdp->nextlist != NULL ||
+                rdp->nextschedlist != NULL ||
+                rdp->waitschedlist != NULL);
 }
 
 int rcu_pending(int cpu)
@@ -1034,7 +1347,9 @@ int rcu_pending(int cpu)
 
         if (rdp->donelist != NULL ||
             !!rdp->waitlistcount ||
-            rdp->nextlist != NULL)
+            rdp->nextlist != NULL ||
+            rdp->nextschedlist != NULL ||
+            rdp->waitschedlist != NULL)
                 return 1;
 
         /* The RCU core needs an acknowledgement from this CPU. */
@@ -1101,6 +1416,11 @@ void __init __rcu_init(void)
                 rdp->donetail = &rdp->donelist;
                 rdp->rcu_flipctr[0] = 0;
                 rdp->rcu_flipctr[1] = 0;
+                rdp->nextschedlist = NULL;
+                rdp->nextschedtail = &rdp->nextschedlist;
+                rdp->waitschedlist = NULL;
+                rdp->waitschedtail = &rdp->waitschedlist;
+                rdp->rcu_sched_sleeping = 0;
         }
         register_cpu_notifier(&rcu_nb);
 
@@ -1123,11 +1443,15 @@ void __init __rcu_init(void)
 }
 
 /*
- * Deprecated, use synchronize_rcu() or synchronize_sched() instead.
+ * Late-boot-time RCU initialization that must wait until after scheduler
+ * has been initialized.
  */
-void synchronize_kernel(void)
+void __init rcu_init_sched(void)
 {
-        synchronize_rcu();
+        rcu_sched_grace_period_task = kthread_run(rcu_sched_grace_period,
+                                                  NULL,
+                                                  "rcu_sched_grace_period");
+        WARN_ON(IS_ERR(rcu_sched_grace_period_task));
 }
 
 #ifdef CONFIG_RCU_TRACE