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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-04-28 20:11:09 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-06-08 18:51:59 -0700
commit6b5fc3a1331810db407c9e0e673dc1837afdc9d0 (patch)
tree00ad3040ed3d6ece09a681ea1e531fdc2a5e4bab /kernel/rcu
parent511324e462a12ea8be1a7e5fc63a992134db80d7 (diff)
downloadlinux-6b5fc3a1331810db407c9e0e673dc1837afdc9d0.tar.bz2
rcu: Add memory barriers for NOCB leader wakeup
Wait/wakeup operations do not guarantee ordering on their own. Instead, either locking or memory barriers are required. This commit therefore adds memory barriers to wake_nocb_leader() and nocb_leader_wait(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Krister Johansen <kjlx@templeofstupid.com> Cc: <stable@vger.kernel.org> # 4.6.x
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree_plugin.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 0b1042545116..573fbe9640a0 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1810,6 +1810,7 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force)
if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) {
/* Prior smp_mb__after_atomic() orders against prior enqueue. */
WRITE_ONCE(rdp_leader->nocb_leader_sleep, false);
+ smp_mb(); /* ->nocb_leader_sleep before swake_up(). */
swake_up(&rdp_leader->nocb_wq);
}
}
@@ -2064,6 +2065,7 @@ wait_again:
* nocb_gp_head, where they await a grace period.
*/
gotcbs = false;
+ smp_mb(); /* wakeup before ->nocb_head reads. */
for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) {
rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head);
if (!rdp->nocb_gp_head)