From: Milton Miller miltonm@us.ibm.com
[ Upstream commit 03cb4d05b4ea9a3491674ca40952adb708d549fa ]
Calling ncsi_stop_channel_monitor from channel_monitor is a guaranteed deadlock on SMP because stop calls del_timer_sync on the timer that invoked channel_monitor as its timer function.
Recognise the inherent race of marking the monitor disabled before deleting the timer by just returning if enable was cleared. After a timeout (the default case -- reset to START when response received) just mark the monitor.enabled false.
If the channel has an entry on the channel_queue list, or if the state is not ACTIVE or INACTIVE, then warn and mark the timer stopped and don't restart, as the locking is broken somehow.
Fixes: 0795fb2021f0 ("net/ncsi: Stop monitor if channel times out or is inactive") Signed-off-by: Milton Miller miltonm@us.ibm.com Signed-off-by: Eddie James eajames@linux.ibm.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/ncsi/ncsi-manage.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/net/ncsi/ncsi-manage.c b/net/ncsi/ncsi-manage.c index 4910e6162232..9bd12f7517ed 100644 --- a/net/ncsi/ncsi-manage.c +++ b/net/ncsi/ncsi-manage.c @@ -103,13 +103,20 @@ static void ncsi_channel_monitor(struct timer_list *t) monitor_state = nc->monitor.state; spin_unlock_irqrestore(&nc->lock, flags);
- if (!enabled || chained) { - ncsi_stop_channel_monitor(nc); - return; - } + if (!enabled) + return; /* expected race disabling timer */ + if (WARN_ON_ONCE(chained)) + goto bad_state; + if (state != NCSI_CHANNEL_INACTIVE && state != NCSI_CHANNEL_ACTIVE) { - ncsi_stop_channel_monitor(nc); +bad_state: + netdev_warn(ndp->ndev.dev, + "Bad NCSI monitor state channel %d 0x%x %s queue\n", + nc->id, state, chained ? "on" : "off"); + spin_lock_irqsave(&nc->lock, flags); + nc->monitor.enabled = false; + spin_unlock_irqrestore(&nc->lock, flags); return; }
@@ -134,10 +141,9 @@ static void ncsi_channel_monitor(struct timer_list *t) ncsi_report_link(ndp, true); ndp->flags |= NCSI_DEV_RESHUFFLE;
- ncsi_stop_channel_monitor(nc); - ncm = &nc->modes[NCSI_MODE_LINK]; spin_lock_irqsave(&nc->lock, flags); + nc->monitor.enabled = false; nc->state = NCSI_CHANNEL_INVISIBLE; ncm->data[2] &= ~0x1; spin_unlock_irqrestore(&nc->lock, flags);