This is a note to let you know that I've just added the patch titled net/ncsi: Avoid channel_monitor hrtimer deadlock to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-ncsi-avoid-channel_monitor-hrtimer-deadlock.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 86a2441dd24df95ccf777fddfe1a64ebedb2971b Author: Milton Miller <miltonm@xxxxxxxxxx> Date: Mon Mar 29 10:20:39 2021 -0500 net/ncsi: Avoid channel_monitor hrtimer deadlock [ 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@xxxxxxxxxx> Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/ncsi/ncsi-manage.c b/net/ncsi/ncsi-manage.c index 28c42b22b748..6b7f9e1f64d3 100644 --- a/net/ncsi/ncsi-manage.c +++ b/net/ncsi/ncsi-manage.c @@ -203,13 +203,20 @@ static void ncsi_channel_monitor(unsigned long data) 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; } @@ -234,10 +241,9 @@ static void ncsi_channel_monitor(unsigned long data) 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);