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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2008-01-25 21:08:24 +0100
committerIngo Molnar <mingo@elte.hu>2008-01-25 21:08:24 +0100
commite0ecfa7917cafe72f4a75f87e8bb5d8d51dc534f (patch)
tree92106dbd88530d3884bc6c4d1c088cba1ad8630e /kernel/rcupdate.c
parent01c1c660f4b8086cad7a62345fd04290f3d82c8f (diff)
Preempt-RCU: fix rcu_barrier for preemptive environment.
Fix rcu_barrier() to work properly in preemptive kernel environment. Also, the ordering of callback must be preserved while moving callbacks to another CPU during CPU hotplug. Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcupdate.c')
-rw-r--r--kernel/rcupdate.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 0ccd0095ebd..760dfc233a0 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -115,7 +115,17 @@ void rcu_barrier(void)
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.
+ */
+ rcu_read_lock();
on_each_cpu(rcu_barrier_func, NULL, 0, 1);
+ rcu_read_unlock();
wait_for_completion(&rcu_barrier_completion);
mutex_unlock(&rcu_barrier_mutex);
}