Commit 03cb4d05 authored by Milton Miller's avatar Milton Miller Committed by David S. Miller
Browse files

net/ncsi: Avoid channel_monitor hrtimer deadlock 



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: 0795fb20 ("net/ncsi: Stop monitor if channel times out or is inactive")
Signed-off-by: default avatarMilton Miller <miltonm@us.ibm.com>
Signed-off-by: default avatarEddie James <eajames@linux.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6e5a03bc

net/ncsi/ncsi-manage.c

+13 −7
Original line number Diff line number Diff line
@@ -105,13 +105,20 @@ 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;

	}
@@ -136,10 +143,9 @@ 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);