Commit-ID: abfd6e58aed4f89fd69b9b17bc4b4527efe3a645
Gitweb: http://git.kernel.org/tip/abfd6e58aed4f89fd69b9b17bc4b4527efe3a645
Author: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
AuthorDate: Thu, 20 Sep 2012 16:59:47 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 23 Oct 2012 14:46:47 -0700
rcu: Fix comment about _rcu_barrier()/orphanage exclusion
In the old days, _rcu_barrier() acquired ->onofflock to exclude
rcu_send_cbs_to_orphanage(), which allowed the latter to avoid memory
barriers in callback handling. However, _rcu_barrier() recently started
doing get_online_cpus() to lock out CPU-hotplug operations entirely, which
means that the comment in rcu_send_cbs_to_orphanage() that talks about
->onofflock is now obsolete. This commit therefore fixes the comment.
Signed-off-by: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcutree.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 74df86b..ac8aed8 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1581,8 +1581,8 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
{
/*
* Orphan the callbacks. First adjust the counts. This is safe
- * because ->onofflock excludes _rcu_barrier()'s adoption of
- * the callbacks, thus no memory barrier is required.
+ * because _rcu_barrier() excludes CPU-hotplug operations, so it
+ * cannot be running now. Thus no memory barrier is required.
*/
if (rdp->nxtlist != NULL) {
rsp->qlen_lazy += rdp->qlen_lazy;
--
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