Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  rcu: Start RCU kthreads in TASK_INTERRUPTIBLE state
  rcu: Remove waitqueue usage for cpu, node, and boost kthreads
  rcu: Avoid acquiring rcu_node locks in timer functions
  atomic: Add atomic_or()
  Documentation: Add statistics about nested locks
  rcu: Decrease memory-barrier usage based on semi-formal proof
  rcu: Make rcu_enter_nohz() pay attention to nesting
  rcu: Don't do reschedule unless in irq
  rcu: Remove old memory barriers from rcu_process_callbacks()
  rcu: Add memory barriers
  rcu: Fix unpaired rcu_irq_enter() from locking selftests

8 files changed, 147 insertions, 151 deletions

diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
index c078ad48f7a1..8173cec473aa 100644
--- a/Documentation/RCU/trace.txt
+++ b/Documentation/RCU/trace.txt
@@ -99,18 +99,11 @@ o	"qp" indicates that RCU still expects a quiescent state from
 
 o       "dt" is the current value of the dyntick counter that is incremented
         when entering or leaving dynticks idle state, either by the
-        scheduler or by irq.  The number after the "/" is the interrupt
-        nesting depth when in dyntick-idle state, or one greater than
-        the interrupt-nesting depth otherwise.
-
-        This field is displayed only for CONFIG_NO_HZ kernels.
-
-o       "dn" is the current value of the dyntick counter that is incremented
-        when entering or leaving dynticks idle state via NMI.  If both
-        the "dt" and "dn" values are even, then this CPU is in dynticks
-        idle mode and may be ignored by RCU.  If either of these two
-        counters is odd, then RCU must be alert to the possibility of
-        an RCU read-side critical section running on this CPU.
+        scheduler or by irq.  This number is even if the CPU is in
+        dyntick idle mode and odd otherwise.  The number after the first
+        "/" is the interrupt nesting depth when in dyntick-idle state,
+        or one greater than the interrupt-nesting depth otherwise.
+        The number after the second "/" is the NMI nesting depth.
 
         This field is displayed only for CONFIG_NO_HZ kernels.
 
diff --git a/Documentation/lockstat.txt b/Documentation/lockstat.txt
index 9c0a80d17a23..cef00d42ed5b 100644
--- a/Documentation/lockstat.txt
+++ b/Documentation/lockstat.txt
@@ -12,8 +12,9 @@ Because things like lock contention can severely impact performance.
 - HOW
 
 Lockdep already has hooks in the lock functions and maps lock instances to
-lock classes. We build on that. The graph below shows the relation between
-the lock functions and the various hooks therein.
+lock classes. We build on that (see Documentation/lockdep-design.txt).
+The graph below shows the relation between the lock functions and the various
+hooks therein.
 
         __acquire
             |
@@ -128,6 +129,37 @@ points are the points we're contending with.
 
 The integer part of the time values is in us.
 
+Dealing with nested locks, subclasses may appear:
+
+32...............................................................................................................................................................................................
+33
+34                               &rq->lock:         13128          13128           0.43         190.53      103881.26          97454        3453404           0.00         401.11    13224683.11
+35                               ---------
+36                               &rq->lock            645          [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
+37                               &rq->lock            297          [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+38                               &rq->lock            360          [<ffffffff8103c4c5>] select_task_rq_fair+0x1f0/0x74a
+39                               &rq->lock            428          [<ffffffff81045f98>] scheduler_tick+0x46/0x1fb
+40                               ---------
+41                               &rq->lock             77          [<ffffffff8103bfc4>] task_rq_lock+0x43/0x75
+42                               &rq->lock            174          [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+43                               &rq->lock           4715          [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
+44                               &rq->lock            893          [<ffffffff81340524>] schedule+0x157/0x7b8
+45
+46...............................................................................................................................................................................................
+47
+48                             &rq->lock/1:         11526          11488           0.33         388.73      136294.31          21461          38404           0.00          37.93      109388.53
+49                             -----------
+50                             &rq->lock/1          11526          [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
+51                             -----------
+52                             &rq->lock/1           5645          [<ffffffff8103ed4b>] double_rq_lock+0x42/0x54
+53                             &rq->lock/1           1224          [<ffffffff81340524>] schedule+0x157/0x7b8
+54                             &rq->lock/1           4336          [<ffffffff8103ed58>] double_rq_lock+0x4f/0x54
+55                             &rq->lock/1            181          [<ffffffff8104ba65>] try_to_wake_up+0x127/0x25a
+
+Line 48 shows statistics for the second subclass (/1) of &rq->lock class
+(subclass starts from 0), since in this case, as line 50 suggests,
+double_rq_lock actually acquires a nested lock of two spinlocks.
+
 View the top contending locks:
 
 # grep : /proc/lock_stat | head
diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 96c038e43d66..ee456c79b0e6 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -34,4 +34,17 @@ static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
 }
 #endif
 
+#ifndef CONFIG_ARCH_HAS_ATOMIC_OR
+static inline void atomic_or(int i, atomic_t *v)
+{
+        int old;
+        int new;
+
+        do {
+                old = atomic_read(v);
+                new = old | i;
+        } while (atomic_cmpxchg(v, old, new) != old);
+}
+#endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR */
+
 #endif /* _LINUX_ATOMIC_H */
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f07d2f03181a..77a7671dd147 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -36,7 +36,7 @@
 #include <linux/interrupt.h>
 #include <linux/sched.h>
 #include <linux/nmi.h>
-#include <asm/atomic.h>
+#include <linux/atomic.h>
 #include <linux/bitops.h>
 #include <linux/module.h>
 #include <linux/completion.h>
@@ -95,7 +95,6 @@ static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
 DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
-static DEFINE_PER_CPU(wait_queue_head_t, rcu_cpu_wq);
 DEFINE_PER_CPU(char, rcu_cpu_has_work);
 static char rcu_kthreads_spawnable;
 
@@ -163,7 +162,7 @@ EXPORT_SYMBOL_GPL(rcu_note_context_switch);
 #ifdef CONFIG_NO_HZ
 DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
         .dynticks_nesting = 1,
-        .dynticks = 1,
+        .dynticks = ATOMIC_INIT(1),
 };
 #endif /* #ifdef CONFIG_NO_HZ */
 
@@ -322,13 +321,25 @@ void rcu_enter_nohz(void)
         unsigned long flags;
         struct rcu_dynticks *rdtp;
 
-        smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
         local_irq_save(flags);
         rdtp = &__get_cpu_var(rcu_dynticks);
-        rdtp->dynticks++;
-        rdtp->dynticks_nesting--;
-        WARN_ON_ONCE(rdtp->dynticks & 0x1);
+        if (--rdtp->dynticks_nesting) {
+                local_irq_restore(flags);
+                return;
+        }
+        /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
+        smp_mb__before_atomic_inc();  /* See above. */
+        atomic_inc(&rdtp->dynticks);
+        smp_mb__after_atomic_inc();  /* Force ordering with next sojourn. */
+        WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
         local_irq_restore(flags);
+
+        /* If the interrupt queued a callback, get out of dyntick mode. */
+        if (in_irq() &&
+            (__get_cpu_var(rcu_sched_data).nxtlist ||
+             __get_cpu_var(rcu_bh_data).nxtlist ||
+             rcu_preempt_needs_cpu(smp_processor_id())))
+                set_need_resched();
 }
 
 /*
@@ -344,11 +355,16 @@ void rcu_exit_nohz(void)
 
         local_irq_save(flags);
         rdtp = &__get_cpu_var(rcu_dynticks);
-        rdtp->dynticks++;
-        rdtp->dynticks_nesting++;
-        WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
+        if (rdtp->dynticks_nesting++) {
+                local_irq_restore(flags);
+                return;
+        }
+        smp_mb__before_atomic_inc();  /* Force ordering w/previous sojourn. */
+        atomic_inc(&rdtp->dynticks);
+        /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
+        smp_mb__after_atomic_inc();  /* See above. */
+        WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
         local_irq_restore(flags);
-        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
 }
 
 /**
@@ -362,11 +378,15 @@ void rcu_nmi_enter(void)
 {
         struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
 
-        if (rdtp->dynticks & 0x1)
+        if (rdtp->dynticks_nmi_nesting == 0 &&
+            (atomic_read(&rdtp->dynticks) & 0x1))
                 return;
-        rdtp->dynticks_nmi++;
-        WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1));
-        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
+        rdtp->dynticks_nmi_nesting++;
+        smp_mb__before_atomic_inc();  /* Force delay from prior write. */
+        atomic_inc(&rdtp->dynticks);
+        /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
+        smp_mb__after_atomic_inc();  /* See above. */
+        WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
 }
 
 /**
@@ -380,11 +400,14 @@ void rcu_nmi_exit(void)
 {
         struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
 
-        if (rdtp->dynticks & 0x1)
+        if (rdtp->dynticks_nmi_nesting == 0 ||
+            --rdtp->dynticks_nmi_nesting != 0)
                 return;
-        smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
-        rdtp->dynticks_nmi++;
-        WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1);
+        /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
+        smp_mb__before_atomic_inc();  /* See above. */
+        atomic_inc(&rdtp->dynticks);
+        smp_mb__after_atomic_inc();  /* Force delay to next write. */
+        WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
 }
 
 /**
@@ -395,13 +418,7 @@ void rcu_nmi_exit(void)
  */
 void rcu_irq_enter(void)
 {
-        struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
-
-        if (rdtp->dynticks_nesting++)
-                return;
-        rdtp->dynticks++;
-        WARN_ON_ONCE(!(rdtp->dynticks & 0x1));
-        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
+        rcu_exit_nohz();
 }
 
 /**
@@ -413,18 +430,7 @@ void rcu_irq_enter(void)
  */
 void rcu_irq_exit(void)
 {
-        struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
-
-        if (--rdtp->dynticks_nesting)
-                return;
-        smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
-        rdtp->dynticks++;
-        WARN_ON_ONCE(rdtp->dynticks & 0x1);
-
-        /* If the interrupt queued a callback, get out of dyntick mode. */
-        if (__this_cpu_read(rcu_sched_data.nxtlist) ||
-            __this_cpu_read(rcu_bh_data.nxtlist))
-                set_need_resched();
+        rcu_enter_nohz();
 }
 
 #ifdef CONFIG_SMP
@@ -436,19 +442,8 @@ void rcu_irq_exit(void)
  */
 static int dyntick_save_progress_counter(struct rcu_data *rdp)
 {
-        int ret;
-        int snap;
-        int snap_nmi;
-
-        snap = rdp->dynticks->dynticks;
-        snap_nmi = rdp->dynticks->dynticks_nmi;
-        smp_mb();       /* Order sampling of snap with end of grace period. */
-        rdp->dynticks_snap = snap;
-        rdp->dynticks_nmi_snap = snap_nmi;
-        ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0);
-        if (ret)
-                rdp->dynticks_fqs++;
-        return ret;
+        rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
+        return 0;
 }
 
 /*
@@ -459,16 +454,11 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp)
  */
 static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 {
-        long curr;
-        long curr_nmi;
-        long snap;
-        long snap_nmi;
+        unsigned long curr;
+        unsigned long snap;
 
-        curr = rdp->dynticks->dynticks;
-        snap = rdp->dynticks_snap;
-        curr_nmi = rdp->dynticks->dynticks_nmi;
-        snap_nmi = rdp->dynticks_nmi_snap;
-        smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
+        curr = (unsigned long)atomic_add_return(0, &rdp->dynticks->dynticks);
+        snap = (unsigned long)rdp->dynticks_snap;
 
         /*
          * If the CPU passed through or entered a dynticks idle phase with
@@ -478,8 +468,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
          * read-side critical section that started before the beginning
          * of the current RCU grace period.
          */
-        if ((curr != snap || (curr & 0x1) == 0) &&
-            (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) {
+        if ((curr & 0x1) == 0 || ULONG_CMP_GE(curr, snap + 2)) {
                 rdp->dynticks_fqs++;
                 return 1;
         }
@@ -908,6 +897,12 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
         unsigned long gp_duration;
 
         WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
+
+        /*
+         * Ensure that all grace-period and pre-grace-period activity
+         * is seen before the assignment to rsp->completed.
+         */
+        smp_mb(); /* See above block comment. */
         gp_duration = jiffies - rsp->gp_start;
         if (gp_duration > rsp->gp_max)
                 rsp->gp_max = gp_duration;
@@ -1455,25 +1450,11 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
  */
 static void rcu_process_callbacks(void)
 {
-        /*
-         * Memory references from any prior RCU read-side critical sections
-         * executed by the interrupted code must be seen before any RCU
-         * grace-period manipulations below.
-         */
-        smp_mb(); /* See above block comment. */
-
         __rcu_process_callbacks(&rcu_sched_state,
                                 &__get_cpu_var(rcu_sched_data));
         __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
         rcu_preempt_process_callbacks();
 
-        /*
-         * Memory references from any later RCU read-side critical sections
-         * executed by the interrupted code must be seen after any RCU
-         * grace-period manipulations above.
-         */
-        smp_mb(); /* See above block comment. */
-
         /* If we are last CPU on way to dyntick-idle mode, accelerate it. */
         rcu_needs_cpu_flush();
 }
@@ -1494,7 +1475,7 @@ static void invoke_rcu_cpu_kthread(void)
                 local_irq_restore(flags);
                 return;
         }
-        wake_up(&__get_cpu_var(rcu_cpu_wq));
+        wake_up_process(__this_cpu_read(rcu_cpu_kthread_task));
         local_irq_restore(flags);
 }
 
@@ -1544,13 +1525,10 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
  */
 static void rcu_cpu_kthread_timer(unsigned long arg)
 {
-        unsigned long flags;
         struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
         struct rcu_node *rnp = rdp->mynode;
 
-        raw_spin_lock_irqsave(&rnp->lock, flags);
-        rnp->wakemask |= rdp->grpmask;
-        raw_spin_unlock_irqrestore(&rnp->lock, flags);
+        atomic_or(rdp->grpmask, &rnp->wakemask);
         invoke_rcu_node_kthread(rnp);
 }
 
@@ -1617,14 +1595,12 @@ static int rcu_cpu_kthread(void *arg)
         unsigned long flags;
         int spincnt = 0;
         unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu);
-        wait_queue_head_t *wqp = &per_cpu(rcu_cpu_wq, cpu);
         char work;
         char *workp = &per_cpu(rcu_cpu_has_work, cpu);
 
         for (;;) {
                 *statusp = RCU_KTHREAD_WAITING;
-                wait_event_interruptible(*wqp,
-                                         *workp != 0 || kthread_should_stop());
+                rcu_wait(*workp != 0 || kthread_should_stop());
                 local_bh_disable();
                 if (rcu_cpu_kthread_should_stop(cpu)) {
                         local_bh_enable();
@@ -1672,10 +1648,10 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
         if (IS_ERR(t))
                 return PTR_ERR(t);
         kthread_bind(t, cpu);
+        set_task_state(t, TASK_INTERRUPTIBLE);
         per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
         WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
         per_cpu(rcu_cpu_kthread_task, cpu) = t;
-        wake_up_process(t);
         sp.sched_priority = RCU_KTHREAD_PRIO;
         sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
         return 0;
@@ -1698,11 +1674,10 @@ static int rcu_node_kthread(void *arg)
 
         for (;;) {
                 rnp->node_kthread_status = RCU_KTHREAD_WAITING;
-                wait_event_interruptible(rnp->node_wq, rnp->wakemask != 0);
+                rcu_wait(atomic_read(&rnp->wakemask) != 0);
                 rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
                 raw_spin_lock_irqsave(&rnp->lock, flags);
-                mask = rnp->wakemask;
-                rnp->wakemask = 0;
+                mask = atomic_xchg(&rnp->wakemask, 0);
                 rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
                 for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) {
                         if ((mask & 0x1) == 0)
@@ -1781,9 +1756,9 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
                 if (IS_ERR(t))
                         return PTR_ERR(t);
                 raw_spin_lock_irqsave(&rnp->lock, flags);
+                set_task_state(t, TASK_INTERRUPTIBLE);
                 rnp->node_kthread_task = t;
                 raw_spin_unlock_irqrestore(&rnp->lock, flags);
-                wake_up_process(t);
                 sp.sched_priority = 99;
                 sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
         }
@@ -1800,21 +1775,16 @@ static int __init rcu_spawn_kthreads(void)
 
         rcu_kthreads_spawnable = 1;
         for_each_possible_cpu(cpu) {
-                init_waitqueue_head(&per_cpu(rcu_cpu_wq, cpu));
                 per_cpu(rcu_cpu_has_work, cpu) = 0;
                 if (cpu_online(cpu))
                         (void)rcu_spawn_one_cpu_kthread(cpu);
         }
         rnp = rcu_get_root(rcu_state);
-        init_waitqueue_head(&rnp->node_wq);
-        rcu_init_boost_waitqueue(rnp);
         (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
-        if (NUM_RCU_NODES > 1)
-                rcu_for_each_leaf_node(rcu_state, rnp) {
-                        init_waitqueue_head(&rnp->node_wq);
-                        rcu_init_boost_waitqueue(rnp);
+        if (NUM_RCU_NODES > 1) {
+                rcu_for_each_leaf_node(rcu_state, rnp)
                         (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
-                }
+        }
         return 0;
 }
 early_initcall(rcu_spawn_kthreads);
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 257664815d5d..7b9a08b4aaea 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -84,11 +84,9 @@
  * Dynticks per-CPU state.
  */
 struct rcu_dynticks {
-        int dynticks_nesting;   /* Track nesting level, sort of. */
-        int dynticks;           /* Even value for dynticks-idle, else odd. */
-        int dynticks_nmi;       /* Even value for either dynticks-idle or */
-                                /*  not in nmi handler, else odd.  So this */
-                                /*  remains even for nmi from irq handler. */
+        int dynticks_nesting;   /* Track irq/process nesting level. */
+        int dynticks_nmi_nesting; /* Track NMI nesting level. */
+        atomic_t dynticks;      /* Even value for dynticks-idle, else odd. */
 };
 
 /* RCU's kthread states for tracing. */
@@ -121,7 +119,9 @@ struct rcu_node {
                                 /*  elements that need to drain to allow the */
                                 /*  current expedited grace period to */
                                 /*  complete (only for TREE_PREEMPT_RCU). */
-        unsigned long wakemask; /* CPUs whose kthread needs to be awakened. */
+        atomic_t wakemask;      /* CPUs whose kthread needs to be awakened. */
+                                /*  Since this has meaning only for leaf */
+                                /*  rcu_node structures, 32 bits suffices. */
         unsigned long qsmaskinit;
                                 /* Per-GP initial value for qsmask & expmask. */
         unsigned long grpmask;  /* Mask to apply to parent qsmask. */
@@ -159,9 +159,6 @@ struct rcu_node {
         struct task_struct *boost_kthread_task;
                                 /* kthread that takes care of priority */
                                 /*  boosting for this rcu_node structure. */
-        wait_queue_head_t boost_wq;
-                                /* Wait queue on which to park the boost */
-                                /*  kthread. */
         unsigned int boost_kthread_status;
                                 /* State of boost_kthread_task for tracing. */
         unsigned long n_tasks_boosted;
@@ -188,9 +185,6 @@ struct rcu_node {
                                 /* kthread that takes care of this rcu_node */
                                 /*  structure, for example, awakening the */
                                 /*  per-CPU kthreads as needed. */
-        wait_queue_head_t node_wq;
-                                /* Wait queue on which to park the per-node */
-                                /*  kthread. */
         unsigned int node_kthread_status;
                                 /* State of node_kthread_task for tracing. */
 } ____cacheline_internodealigned_in_smp;
@@ -284,7 +278,6 @@ struct rcu_data {
         /* 3) dynticks interface. */
         struct rcu_dynticks *dynticks;  /* Shared per-CPU dynticks state. */
         int dynticks_snap;              /* Per-GP tracking for dynticks. */
-        int dynticks_nmi_snap;          /* Per-GP tracking for dynticks_nmi. */
 #endif /* #ifdef CONFIG_NO_HZ */
 
         /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
@@ -337,6 +330,16 @@ struct rcu_data {
                                                 /*  scheduling clock irq */
                                                 /*  before ratting on them. */
 
+#define rcu_wait(cond)                                                  \
+do {                                                                    \
+        for (;;) {                                                      \
+                set_current_state(TASK_INTERRUPTIBLE);                  \
+                if (cond)                                               \
+                        break;                                          \
+                schedule();                                             \
+        }                                                               \
+        __set_current_state(TASK_RUNNING);                              \
+} while (0)
 
 /*
  * RCU global state, including node hierarchy.  This hierarchy is
@@ -446,7 +449,6 @@ static void __cpuinit rcu_preempt_init_percpu_data(int cpu);
 static void rcu_preempt_send_cbs_to_online(void);
 static void __init __rcu_init_preempt(void);
 static void rcu_needs_cpu_flush(void);
-static void __init rcu_init_boost_waitqueue(struct rcu_node *rnp);
 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
                                           cpumask_var_t cm);
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 3f6559a5f5cd..a767b7dac365 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1196,8 +1196,7 @@ static int rcu_boost_kthread(void *arg)
 
         for (;;) {
                 rnp->boost_kthread_status = RCU_KTHREAD_WAITING;
-                wait_event_interruptible(rnp->boost_wq, rnp->boost_tasks ||
-                                                        rnp->exp_tasks);
+                rcu_wait(rnp->boost_tasks || rnp->exp_tasks);
                 rnp->boost_kthread_status = RCU_KTHREAD_RUNNING;
                 more2boost = rcu_boost(rnp);
                 if (more2boost)
@@ -1275,14 +1274,6 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
 }
 
 /*
- * Initialize the RCU-boost waitqueue.
- */
-static void __init rcu_init_boost_waitqueue(struct rcu_node *rnp)
-{
-        init_waitqueue_head(&rnp->boost_wq);
-}
-
-/*
  * 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.
@@ -1304,9 +1295,9 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
         if (IS_ERR(t))
                 return PTR_ERR(t);
         raw_spin_lock_irqsave(&rnp->lock, flags);
+        set_task_state(t, TASK_INTERRUPTIBLE);
         rnp->boost_kthread_task = t;
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
-        wake_up_process(t);
         sp.sched_priority = RCU_KTHREAD_PRIO;
         sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
         return 0;
@@ -1328,10 +1319,6 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
 {
 }
 
-static void __init rcu_init_boost_waitqueue(struct rcu_node *rnp)
-{
-}
-
 static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
                                                  struct rcu_node *rnp,
                                                  int rnp_index)
@@ -1520,7 +1507,6 @@ int rcu_needs_cpu(int cpu)
 {
         int c = 0;
         int snap;
-        int snap_nmi;
         int thatcpu;
 
         /* Check for being in the holdoff period. */
@@ -1531,10 +1517,10 @@ int rcu_needs_cpu(int cpu)
         for_each_online_cpu(thatcpu) {
                 if (thatcpu == cpu)
                         continue;
-                snap = per_cpu(rcu_dynticks, thatcpu).dynticks;
-                snap_nmi = per_cpu(rcu_dynticks, thatcpu).dynticks_nmi;
+                snap = atomic_add_return(0, &per_cpu(rcu_dynticks,
+                                                     thatcpu).dynticks);
                 smp_mb(); /* Order sampling of snap with end of grace period. */
-                if (((snap & 0x1) != 0) || ((snap_nmi & 0x1) != 0)) {
+                if ((snap & 0x1) != 0) {
                         per_cpu(rcu_dyntick_drain, cpu) = 0;
                         per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
                         return rcu_needs_cpu_quick_check(cpu);
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index aa0fd72b4bc7..9678cc3650f5 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -69,10 +69,10 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
                    rdp->passed_quiesc, rdp->passed_quiesc_completed,
                    rdp->qs_pending);
 #ifdef CONFIG_NO_HZ
-        seq_printf(m, " dt=%d/%d dn=%d df=%lu",
-                   rdp->dynticks->dynticks,
+        seq_printf(m, " dt=%d/%d/%d df=%lu",
+                   atomic_read(&rdp->dynticks->dynticks),
                    rdp->dynticks->dynticks_nesting,
-                   rdp->dynticks->dynticks_nmi,
+                   rdp->dynticks->dynticks_nmi_nesting,
                    rdp->dynticks_fqs);
 #endif /* #ifdef CONFIG_NO_HZ */
         seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi);
@@ -141,9 +141,9 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
                    rdp->qs_pending);
 #ifdef CONFIG_NO_HZ
         seq_printf(m, ",%d,%d,%d,%lu",
-                   rdp->dynticks->dynticks,
+                   atomic_read(&rdp->dynticks->dynticks),
                    rdp->dynticks->dynticks_nesting,
-                   rdp->dynticks->dynticks_nmi,
+                   rdp->dynticks->dynticks_nmi_nesting,
                    rdp->dynticks_fqs);
 #endif /* #ifdef CONFIG_NO_HZ */
         seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi);
@@ -167,7 +167,7 @@ static int show_rcudata_csv(struct seq_file *m, void *unused)
 {
         seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pqc\",\"pq\",");
 #ifdef CONFIG_NO_HZ
-        seq_puts(m, "\"dt\",\"dt nesting\",\"dn\",\"df\",");
+        seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\",");
 #endif /* #ifdef CONFIG_NO_HZ */
         seq_puts(m, "\"of\",\"ri\",\"ql\",\"b\",\"ci\",\"co\",\"ca\"\n");
 #ifdef CONFIG_TREE_PREEMPT_RCU
diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 619313ed6c46..507a22fab738 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -144,7 +144,7 @@ static void init_shared_classes(void)
 
 #define HARDIRQ_ENTER()                         \
         local_irq_disable();                    \
-        irq_enter();                            \
+        __irq_enter();                          \
         WARN_ON(!in_irq());
 
 #define HARDIRQ_EXIT()                          \