trace: set max latency variable to zero on default

[safe/jmp/linux-2.6] / kernel / rcupdate.c

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 0ccd009..d92a76a 100644 (file)
--- 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};
@@ -56,8 +56,11 @@ static atomic_t rcu_barrier_cpu_count;
 static DEFINE_MUTEX(rcu_barrier_mutex);
 static struct completion rcu_barrier_completion;
 
-/* Because of FASTCALL declaration of complete, we use this wrapper */
-static void wakeme_after_rcu(struct rcu_head  *head)
+/*
+ * Awaken the corresponding synchronize_rcu() instance now that a
+ * grace period has elapsed.
+ */
+void wakeme_after_rcu(struct rcu_head  *head)
 {
        struct rcu_synchronize *rcu;
 
@@ -77,12 +80,10 @@ static void wakeme_after_rcu(struct rcu_head  *head)
 void synchronize_rcu(void)
 {
        struct rcu_synchronize rcu;
-
        init_completion(&rcu.completion);
-       /* Will wake me after RCU finished */
+       /* Will wake me after RCU finished. */
        call_rcu(&rcu.head, wakeme_after_rcu);
-
-       /* Wait for it */
+       /* Wait for it. */
        wait_for_completion(&rcu.completion);
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu);
@@ -96,31 +97,79 @@ 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 */
        mutex_lock(&rcu_barrier_mutex);
        init_completion(&rcu_barrier_completion);
-       atomic_set(&rcu_barrier_cpu_count, 0);
-       on_each_cpu(rcu_barrier_func, NULL, 0, 1);
+       /*
+        * Initialize rcu_barrier_cpu_count to 1, then invoke
+        * rcu_barrier_func() on each CPU, so that each CPU also has
+        * incremented rcu_barrier_cpu_count.  Only then is it safe to
+        * decrement rcu_barrier_cpu_count -- otherwise the first CPU
+        * might complete its grace period before all of the other CPUs
+        * did their increment, causing this function to return too
+        * early.
+        */
+       atomic_set(&rcu_barrier_cpu_count, 1);
+       on_each_cpu(rcu_barrier_func, (void *)type, 1);
+       if (atomic_dec_and_test(&rcu_barrier_cpu_count))
+               complete(&rcu_barrier_completion);
        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();