Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
rcupdate: fix bug of rcu_barrier*()
profiling: fix !procfs build
Fixed trivial conflicts in 'include/linux/profile.h'
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 467d594..ad63af8 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -119,18 +119,19 @@
/* 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);
/*
- * The queueing of callbacks in all CPUs must be atomic with
- * respect to RCU, otherwise one CPU may queue a callback,
- * wait for a grace period, decrement barrier count and call
- * complete(), while other CPUs have not yet queued anything.
- * So, we need to make sure that grace periods cannot complete
- * until all the callbacks are queued.
+ * 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.
*/
- rcu_read_lock();
+ atomic_set(&rcu_barrier_cpu_count, 1);
on_each_cpu(rcu_barrier_func, (void *)type, 1);
- rcu_read_unlock();
+ if (atomic_dec_and_test(&rcu_barrier_cpu_count))
+ complete(&rcu_barrier_completion);
wait_for_completion(&rcu_barrier_completion);
mutex_unlock(&rcu_barrier_mutex);
}
