mac80211: use synchronize_rcu() with rcu_barrier()

The RCU docs used to state that rcu_barrier() included a wait
for an RCU grace period; however the comments for rcu_barrier()
as of commit f0a0e6f... "rcu: Clarify memory-ordering properties
of grace-period primitives" contradict this.

So add back synchronize_{rcu,net}() to where they once were,
but keep the rcu_barrier()s for the call_rcu() callbacks.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Bob Copeland <bob@cozybit.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 146b1320af4e..9daa64ee337e 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -839,11 +839,12 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
                  *
                  * sta_info_flush_cleanup() requires rcu_barrier()
                  * first to wait for the station call_rcu() calls
-                 * to complete, here we need at least sychronize_rcu()
-                 * it to wait for the RX path in case it is using the
+                 * to complete, and we also need synchronize_rcu()
+                 * to wait for the RX path in case it is using the
                  * interface and enqueuing frames at this very time on
                  * another CPU.
                  */
+                synchronize_rcu();
                 rcu_barrier();
                 sta_info_flush_cleanup(sdata);