7 files changed, 561 insertions, 77 deletions

diff --git a/kernel/pid.c b/kernel/pid.c
index 20d59fa2d493..30bd5d4b2ac7 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -30,6 +30,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/init.h>
+#include <linux/rculist.h>
 #include <linux/bootmem.h>
 #include <linux/hash.h>
 #include <linux/pid_namespace.h>
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index f4ffbd0f306f..d8348792f9f5 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -502,10 +502,38 @@ void rcu_check_callbacks(int cpu, int user)
         if (user ||
             (idle_cpu(cpu) && !in_softirq() &&
                                 hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+
+                /*
+                 * Get here if this CPU took its interrupt from user
+                 * mode or from the idle loop, and if this is not a
+                 * nested interrupt.  In this case, the CPU is in
+                 * a quiescent state, so count it.
+                 *
+                 * Also do a memory barrier.  This 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.  The memory barrier makes sure that
+                 * the rcu_qsctr_inc() and rcu_bh_qsctr_inc() are see
+                 * by other CPUs to happen after any such write.
+                 */
+
+                smp_mb();  /* See above block comment. */
                 rcu_qsctr_inc(cpu);
                 rcu_bh_qsctr_inc(cpu);
-        } else if (!in_softirq())
+
+        } else if (!in_softirq()) {
+
+                /*
+                 * Get here if this CPU did not take its interrupt from
+                 * softirq, in other words, if it is not interrupting
+                 * a rcu_bh read-side critical section.  This is an _bh
+                 * critical section, so count it.  The memory barrier
+                 * is needed for the same reason as is the above one.
+                 */
+
+                smp_mb();  /* See above block comment. */
                 rcu_bh_qsctr_inc(cpu);
+        }
         raise_rcu_softirq();
 }
 
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index c09605f8d16c..4a74b8d48d90 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -39,16 +39,16 @@
 #include <linux/sched.h>
 #include <asm/atomic.h>
 #include <linux/bitops.h>
-#include <linux/completion.h>
 #include <linux/percpu.h>
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/mutex.h>
 #include <linux/module.h>
 
-struct rcu_synchronize {
-        struct rcu_head head;
-        struct completion completion;
+enum rcu_barrier {
+        RCU_BARRIER_STD,
+        RCU_BARRIER_BH,
+        RCU_BARRIER_SCHED,
 };
 
 static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
@@ -60,7 +60,7 @@ static struct completion rcu_barrier_completion;
  * Awaken the corresponding synchronize_rcu() instance now that a
  * grace period has elapsed.
  */
-static void wakeme_after_rcu(struct rcu_head  *head)
+void wakeme_after_rcu(struct rcu_head  *head)
 {
         struct rcu_synchronize *rcu;
 
@@ -77,17 +77,7 @@ static void wakeme_after_rcu(struct rcu_head  *head)
  * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
  * and may be nested.
  */
-void synchronize_rcu(void)
-{
-        struct rcu_synchronize rcu;
-
-        init_completion(&rcu.completion);
-        /* Will wake me after RCU finished */
-        call_rcu(&rcu.head, wakeme_after_rcu);
-
-        /* Wait for it */
-        wait_for_completion(&rcu.completion);
-}
+synchronize_rcu_xxx(synchronize_rcu, call_rcu)
 EXPORT_SYMBOL_GPL(synchronize_rcu);
 
 static void rcu_barrier_callback(struct rcu_head *notused)
@@ -99,19 +89,30 @@ static void rcu_barrier_callback(struct rcu_head *notused)
 /*
  * Called with preemption disabled, and from cross-cpu IRQ context.
  */
-static void rcu_barrier_func(void *notused)
+static void rcu_barrier_func(void *type)
 {
         int cpu = smp_processor_id();
         struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
 
         atomic_inc(&rcu_barrier_cpu_count);
-        call_rcu(head, rcu_barrier_callback);
+        switch ((enum rcu_barrier)type) {
+        case RCU_BARRIER_STD:
+                call_rcu(head, rcu_barrier_callback);
+                break;
+        case RCU_BARRIER_BH:
+                call_rcu_bh(head, rcu_barrier_callback);
+                break;
+        case RCU_BARRIER_SCHED:
+                call_rcu_sched(head, rcu_barrier_callback);
+                break;
+        }
 }
 
-/**
- * rcu_barrier - Wait until all the in-flight RCUs are complete.
+/*
+ * Orchestrate the specified type of RCU barrier, waiting for all
+ * RCU callbacks of the specified type to complete.
  */
-void rcu_barrier(void)
+static void _rcu_barrier(enum rcu_barrier type)
 {
         BUG_ON(in_interrupt());
         /* Take cpucontrol mutex to protect against CPU hotplug */
@@ -127,13 +128,39 @@ void rcu_barrier(void)
          * until all the callbacks are queued.
          */
         rcu_read_lock();
-        on_each_cpu(rcu_barrier_func, NULL, 0, 1);
+        on_each_cpu(rcu_barrier_func, (void *)type, 0, 1);
         rcu_read_unlock();
         wait_for_completion(&rcu_barrier_completion);
         mutex_unlock(&rcu_barrier_mutex);
 }
+
+/**
+ * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
+ */
+void rcu_barrier(void)
+{
+        _rcu_barrier(RCU_BARRIER_STD);
+}
 EXPORT_SYMBOL_GPL(rcu_barrier);
 
+/**
+ * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
+ */
+void rcu_barrier_bh(void)
+{
+        _rcu_barrier(RCU_BARRIER_BH);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+
+/**
+ * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
+ */
+void rcu_barrier_sched(void)
+{
+        _rcu_barrier(RCU_BARRIER_SCHED);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+
 void __init rcu_init(void)
 {
         __rcu_init();
diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index 5e02b7740702..396b121edfe5 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;
 
@@ -916,22 +1044,40 @@ 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);
 }
 
 void __devinit 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);
 }
 
 #else /* #ifdef CONFIG_HOTPLUG_CPU */
@@ -986,31 +1132,196 @@ 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
@@ -1027,7 +1338,9 @@ 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)
@@ -1038,7 +1351,9 @@ 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. */
@@ -1105,6 +1420,11 @@ 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);
 
@@ -1127,11 +1447,15 @@ 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
diff --git a/kernel/rcupreempt_trace.c b/kernel/rcupreempt_trace.c
index 49ac4947af24..5edf82c34bbc 100644
--- a/kernel/rcupreempt_trace.c
+++ b/kernel/rcupreempt_trace.c
@@ -38,7 +38,6 @@
 #include <linux/moduleparam.h>
 #include <linux/percpu.h>
 #include <linux/notifier.h>
-#include <linux/rcupdate.h>
 #include <linux/cpu.h>
 #include <linux/mutex.h>
 #include <linux/rcupreempt_trace.h>
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 33acc424667e..5e954edf0ed5 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -57,7 +57,8 @@ static int stat_interval;	/* Interval between stats, in seconds. */
                                 /*  Defaults to "only at end of test". */
 static int verbose;             /* Print more debug info. */
 static int test_no_idle_hz;     /* Test RCU's support for tickless idle CPUs. */
-static int shuffle_interval = 5; /* Interval between shuffles (in sec)*/
+static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
+static int stutter = 5;         /* Start/stop testing interval (in sec) */
 static char *torture_type = "rcu"; /* What RCU implementation to torture. */
 
 module_param(nreaders, int, 0444);
@@ -72,6 +73,8 @@ module_param(test_no_idle_hz, bool, 0444);
 MODULE_PARM_DESC(test_no_idle_hz, "Test support for tickless idle CPUs");
 module_param(shuffle_interval, int, 0444);
 MODULE_PARM_DESC(shuffle_interval, "Number of seconds between shuffles");
+module_param(stutter, int, 0444);
+MODULE_PARM_DESC(stutter, "Number of seconds to run/halt test");
 module_param(torture_type, charp, 0444);
 MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
 
@@ -91,6 +94,7 @@ static struct task_struct **fakewriter_tasks;
 static struct task_struct **reader_tasks;
 static struct task_struct *stats_task;
 static struct task_struct *shuffler_task;
+static struct task_struct *stutter_task;
 
 #define RCU_TORTURE_PIPE_LEN 10
 
@@ -119,6 +123,15 @@ static atomic_t n_rcu_torture_mberror;
 static atomic_t n_rcu_torture_error;
 static struct list_head rcu_torture_removed;
 
+static int stutter_pause_test = 0;
+
+#if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
+#define RCUTORTURE_RUNNABLE_INIT 1
+#else
+#define RCUTORTURE_RUNNABLE_INIT 0
+#endif
+int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
+
 /*
  * Allocate an element from the rcu_tortures pool.
  */
@@ -179,6 +192,16 @@ rcu_random(struct rcu_random_state *rrsp)
         return swahw32(rrsp->rrs_state);
 }
 
+static void
+rcu_stutter_wait(void)
+{
+        while (stutter_pause_test || !rcutorture_runnable)
+                if (rcutorture_runnable)
+                        schedule_timeout_interruptible(1);
+                else
+                        schedule_timeout_interruptible(round_jiffies_relative(HZ));
+}
+
 /*
  * Operations vector for selecting different types of tests.
  */
@@ -192,6 +215,7 @@ struct rcu_torture_ops {
         int (*completed)(void);
         void (*deferredfree)(struct rcu_torture *p);
         void (*sync)(void);
+        void (*cb_barrier)(void);
         int (*stats)(char *page);
         char *name;
 };
@@ -265,6 +289,7 @@ static struct rcu_torture_ops rcu_ops = {
         .completed = rcu_torture_completed,
         .deferredfree = rcu_torture_deferred_free,
         .sync = synchronize_rcu,
+        .cb_barrier = rcu_barrier,
         .stats = NULL,
         .name = "rcu"
 };
@@ -304,6 +329,7 @@ static struct rcu_torture_ops rcu_sync_ops = {
         .completed = rcu_torture_completed,
         .deferredfree = rcu_sync_torture_deferred_free,
         .sync = synchronize_rcu,
+        .cb_barrier = NULL,
         .stats = NULL,
         .name = "rcu_sync"
 };
@@ -364,6 +390,7 @@ static struct rcu_torture_ops rcu_bh_ops = {
         .completed = rcu_bh_torture_completed,
         .deferredfree = rcu_bh_torture_deferred_free,
         .sync = rcu_bh_torture_synchronize,
+        .cb_barrier = rcu_barrier_bh,
         .stats = NULL,
         .name = "rcu_bh"
 };
@@ -377,6 +404,7 @@ static struct rcu_torture_ops rcu_bh_sync_ops = {
         .completed = rcu_bh_torture_completed,
         .deferredfree = rcu_sync_torture_deferred_free,
         .sync = rcu_bh_torture_synchronize,
+        .cb_barrier = NULL,
         .stats = NULL,
         .name = "rcu_bh_sync"
 };
@@ -458,6 +486,7 @@ static struct rcu_torture_ops srcu_ops = {
         .completed = srcu_torture_completed,
         .deferredfree = rcu_sync_torture_deferred_free,
         .sync = srcu_torture_synchronize,
+        .cb_barrier = NULL,
         .stats = srcu_torture_stats,
         .name = "srcu"
 };
@@ -482,6 +511,11 @@ static int sched_torture_completed(void)
         return 0;
 }
 
+static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
+{
+        call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
+}
+
 static void sched_torture_synchronize(void)
 {
         synchronize_sched();
@@ -494,12 +528,27 @@ static struct rcu_torture_ops sched_ops = {
         .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
         .readunlock = sched_torture_read_unlock,
         .completed = sched_torture_completed,
-        .deferredfree = rcu_sync_torture_deferred_free,
+        .deferredfree = rcu_sched_torture_deferred_free,
         .sync = sched_torture_synchronize,
+        .cb_barrier = rcu_barrier_sched,
         .stats = NULL,
         .name = "sched"
 };
 
+static struct rcu_torture_ops sched_ops_sync = {
+        .init = rcu_sync_torture_init,
+        .cleanup = NULL,
+        .readlock = sched_torture_read_lock,
+        .readdelay = rcu_read_delay,  /* just reuse rcu's version. */
+        .readunlock = sched_torture_read_unlock,
+        .completed = sched_torture_completed,
+        .deferredfree = rcu_sync_torture_deferred_free,
+        .sync = sched_torture_synchronize,
+        .cb_barrier = NULL,
+        .stats = NULL,
+        .name = "sched_sync"
+};
+
 /*
  * RCU torture writer kthread.  Repeatedly substitutes a new structure
  * for that pointed to by rcu_torture_current, freeing the old structure
@@ -537,6 +586,7 @@ rcu_torture_writer(void *arg)
                 }
                 rcu_torture_current_version++;
                 oldbatch = cur_ops->completed();
+                rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
         while (!kthread_should_stop())
@@ -560,6 +610,7 @@ rcu_torture_fakewriter(void *arg)
                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
                 udelay(rcu_random(&rand) & 0x3ff);
                 cur_ops->sync();
+                rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
 
         VERBOSE_PRINTK_STRING("rcu_torture_fakewriter task stopping");
@@ -615,6 +666,7 @@ rcu_torture_reader(void *arg)
                 preempt_enable();
                 cur_ops->readunlock(idx);
                 schedule();
+                rcu_stutter_wait();
         } while (!kthread_should_stop() && !fullstop);
         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
         while (!kthread_should_stop())
@@ -661,6 +713,7 @@ rcu_torture_printk(char *page)
         if (i > 1) {
                 cnt += sprintf(&page[cnt], "!!! ");
                 atomic_inc(&n_rcu_torture_error);
+                WARN_ON_ONCE(1);
         }
         cnt += sprintf(&page[cnt], "Reader Pipe: ");
         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
@@ -785,15 +838,34 @@ rcu_torture_shuffle(void *arg)
         return 0;
 }
 
+/* Cause the rcutorture test to "stutter", starting and stopping all
+ * threads periodically.
+ */
+static int
+rcu_torture_stutter(void *arg)
+{
+        VERBOSE_PRINTK_STRING("rcu_torture_stutter task started");
+        do {
+                schedule_timeout_interruptible(stutter * HZ);
+                stutter_pause_test = 1;
+                if (!kthread_should_stop())
+                        schedule_timeout_interruptible(stutter * HZ);
+                stutter_pause_test = 0;
+        } while (!kthread_should_stop());
+        VERBOSE_PRINTK_STRING("rcu_torture_stutter task stopping");
+        return 0;
+}
+
 static inline void
 rcu_torture_print_module_parms(char *tag)
 {
         printk(KERN_ALERT "%s" TORTURE_FLAG
                 "--- %s: nreaders=%d nfakewriters=%d "
                 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
-                "shuffle_interval = %d\n",
+                "shuffle_interval=%d stutter=%d\n",
                 torture_type, tag, nrealreaders, nfakewriters,
-                stat_interval, verbose, test_no_idle_hz, shuffle_interval);
+                stat_interval, verbose, test_no_idle_hz, shuffle_interval,
+                stutter);
 }
 
 static void
@@ -802,6 +874,11 @@ rcu_torture_cleanup(void)
         int i;
 
         fullstop = 1;
+        if (stutter_task) {
+                VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
+                kthread_stop(stutter_task);
+        }
+        stutter_task = NULL;
         if (shuffler_task) {
                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_shuffle task");
                 kthread_stop(shuffler_task);
@@ -848,7 +925,9 @@ rcu_torture_cleanup(void)
         stats_task = NULL;
 
         /* Wait for all RCU callbacks to fire.  */
-        rcu_barrier();
+
+        if (cur_ops->cb_barrier != NULL)
+                cur_ops->cb_barrier();
 
         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
 
@@ -868,7 +947,7 @@ rcu_torture_init(void)
         int firsterr = 0;
         static struct rcu_torture_ops *torture_ops[] =
                 { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
-                  &srcu_ops, &sched_ops, };
+                  &srcu_ops, &sched_ops, &sched_ops_sync, };
 
         /* Process args and tell the world that the torturer is on the job. */
         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
@@ -988,6 +1067,19 @@ rcu_torture_init(void)
                         goto unwind;
                 }
         }
+        if (stutter < 0)
+                stutter = 0;
+        if (stutter) {
+                /* Create the stutter thread */
+                stutter_task = kthread_run(rcu_torture_stutter, NULL,
+                                          "rcu_torture_stutter");
+                if (IS_ERR(stutter_task)) {
+                        firsterr = PTR_ERR(stutter_task);
+                        VERBOSE_PRINTK_ERRSTRING("Failed to create stutter");
+                        stutter_task = NULL;
+                        goto unwind;
+                }
+        }
         return 0;
 
 unwind:
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 29116652dca8..c6887cf135c8 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -82,6 +82,9 @@ extern int maps_protect;
 extern int sysctl_stat_interval;
 extern int latencytop_enabled;
 extern int sysctl_nr_open_min, sysctl_nr_open_max;
+#ifdef CONFIG_RCU_TORTURE_TEST
+extern int rcutorture_runnable;
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
 
 /* Constants used for minimum and  maximum */
 #if defined(CONFIG_DETECT_SOFTLOCKUP) || defined(CONFIG_HIGHMEM)
@@ -813,6 +816,16 @@ static struct ctl_table kern_table[] = {
                 .child          = key_sysctls,
         },
 #endif
+#ifdef CONFIG_RCU_TORTURE_TEST
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "rcutorture_runnable",
+                .data           = &rcutorture_runnable,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
+#endif
 /*
  * NOTE: do not add new entries to this table unless you have read
  * Documentation/sysctl/ctl_unnumbered.txt