| From foo@baz Sun Oct 12 20:11:55 CEST 2014 |
| From: Joe Lawrence <Joe.Lawrence@stratus.com> |
| Date: Fri, 3 Oct 2014 09:58:34 -0400 |
| Subject: team: avoid race condition in scheduling delayed work |
| |
| From: Joe Lawrence <Joe.Lawrence@stratus.com> |
| |
| [ Upstream commit 47549650abd13d873fd2e5fc218db19e21031074 ] |
| |
| 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 <joe.lawrence@stratus.com> |
| Acked-by: Jiri Pirko <jiri@resnulli.us> |
| Fixes: fc423ff00df3a19554414ee ("team: add peer notification") |
| Fixes: 492b200efdd20b8fcfdac87 ("team: add support for sending multicast rejoins") |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/net/team/team.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| --- a/drivers/net/team/team.c |
| +++ b/drivers/net/team/team.c |
| @@ -647,7 +647,7 @@ static void team_notify_peers(struct tea |
| { |
| 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 tea |
| { |
| 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); |
| } |
| |
