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

1 files changed, 5 insertions, 19 deletions

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);