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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@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2012-09-20 16:59:47 -07:00 committed by Paul E. McKenney
parent 6f0c0580b7
commit abfd6e58ae
1 changed files with 2 additions and 2 deletions
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4
kernel/rcutree.c
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@ -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 * Orphan the callbacks. First adjust the counts. This is safe
* because ->onofflock excludes _rcu_barrier()'s adoption of * because _rcu_barrier() excludes CPU-hotplug operations, so it
* the callbacks, thus no memory barrier is required. * cannot be running now. Thus no memory barrier is required.
*/ */
if (rdp->nxtlist != NULL) { if (rdp->nxtlist != NULL) {
rsp->qlen_lazy += rdp->qlen_lazy; rsp->qlen_lazy += rdp->qlen_lazy;