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authorPaul E. McKenney <paulmck@linux.ibm.com>2019-05-14 01:57:50 +0300
committerPaul E. McKenney <paulmck@linux.ibm.com>2019-08-14 00:35:49 +0300
commite6060b41c9955374079926a7612b857a8458ed1f (patch)
tree297581f29d4caec633aa474b3b4dc30f16e5cffe /kernel/rcu/rcu_segcblist.c
parent76c6927c3ee443e756f2c0c9f992cb04b26c65f2 (diff)
downloadlinux-e6060b41c9955374079926a7612b857a8458ed1f.tar.xz
rcu/nocb: Allow lockless use of rcu_segcblist_empty()
Currently, rcu_segcblist_empty() assumes that the callback list is not being changed by other CPUs, but upcoming changes will require it to operate locklessly. This commit therefore adds the needed READ_ONCE() call, along with the WRITE_ONCE() calls when updating the callback list's ->head field. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Diffstat (limited to 'kernel/rcu/rcu_segcblist.c')
-rw-r--r--kernel/rcu/rcu_segcblist.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
index 0e7fe678b6ac..06435a368be5 100644
--- a/kernel/rcu/rcu_segcblist.c
+++ b/kernel/rcu/rcu_segcblist.c
@@ -213,7 +213,7 @@ void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
if (!rcu_segcblist_ready_cbs(rsclp))
return; /* Nothing to do. */
*rclp->tail = rsclp->head;
- rsclp->head = *rsclp->tails[RCU_DONE_TAIL];
+ WRITE_ONCE(rsclp->head, *rsclp->tails[RCU_DONE_TAIL]);
WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL);
rclp->tail = rsclp->tails[RCU_DONE_TAIL];
for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--)
@@ -268,7 +268,7 @@ void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
if (!rclp->head)
return; /* No callbacks to move. */
*rclp->tail = rsclp->head;
- rsclp->head = rclp->head;
+ WRITE_ONCE(rsclp->head, rclp->head);
for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
if (&rsclp->head == rsclp->tails[i])
WRITE_ONCE(rsclp->tails[i], rclp->tail);