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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: 0795fb2021 ("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>
This commit is contained in:
Milton Miller 2021-03-29 10:20:39 -05:00 committed by David S. Miller
parent 6e5a03bcba
commit 03cb4d05b4
1 changed files with 13 additions and 7 deletions
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20
net/ncsi/ncsi-manage.c
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@ -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);