From 47549650abd13d873fd2e5fc218db19e21031074 Mon Sep 17 00:00:00 2001 From: Joe Lawrence Date: Fri, 3 Oct 2014 09:58:34 -0400 Subject: [PATCH] team: avoid race condition in scheduling delayed work When team_notify_peers and team_mcast_rejoin are called, they both reset their respective .count_pending atomic variable. Then when the actual worker function is executed, the variable is atomically decremented. This pattern introduces a potential race condition where the .count_pending rolls over and the worker function keeps rescheduling until .count_pending decrements to zero again: THREAD 1 THREAD 2 ======== ======== team_notify_peers(teamX) atomic_set count_pending = 1 schedule_delayed_work team_notify_peers(teamX) atomic_set count_pending = 1 team_notify_peers_work atomic_dec_and_test count_pending = 0 (return) schedule_delayed_work team_notify_peers_work atomic_dec_and_test count_pending = -1 schedule_delayed_work (repeat until count_pending = 0) Instead of assigning a new value to .count_pending, use atomic_add to tack-on the additional desired worker function invocations. Signed-off-by: Joe Lawrence Acked-by: Jiri Pirko Fixes: fc423ff00df3a19554414ee ("team: add peer notification") Fixes: 492b200efdd20b8fcfdac87 ("team: add support for sending multicast rejoins") Signed-off-by: David S. Miller --- drivers/net/team/team.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c index ef10302ec936..1f76c2ea53f2 100644 --- a/drivers/net/team/team.c +++ b/drivers/net/team/team.c @@ -647,7 +647,7 @@ static void team_notify_peers(struct team *team) { if (!team->notify_peers.count || !netif_running(team->dev)) return; - atomic_set(&team->notify_peers.count_pending, team->notify_peers.count); + atomic_add(team->notify_peers.count, &team->notify_peers.count_pending); schedule_delayed_work(&team->notify_peers.dw, 0); } @@ -687,7 +687,7 @@ static void team_mcast_rejoin(struct team *team) { if (!team->mcast_rejoin.count || !netif_running(team->dev)) return; - atomic_set(&team->mcast_rejoin.count_pending, team->mcast_rejoin.count); + atomic_add(team->mcast_rejoin.count, &team->mcast_rejoin.count_pending); schedule_delayed_work(&team->mcast_rejoin.dw, 0); }