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Message-Id: <20210329152039.15189-1-eajames@linux.ibm.com>
Date: Mon, 29 Mar 2021 10:20:39 -0500
From: Eddie James <eajames@...ux.ibm.com>
To: sam@...dozajonas.com
Cc: davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, Milton Miller <miltonm@...ibm.com>,
Eddie James <eajames@...ux.ibm.com>
Subject: [PATCH] net/ncsi: Avoid channel_monitor hrtimer deadlock
From: Milton Miller <miltonm@...ibm.com>
Calling ncsi_stop_channel_monitor from channel_monitor is a guaranteed
deadlock on SMP because stop calls del_timer_sync on the timer that
inoked 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 entrie 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@...ibm.com>
Signed-off-by: Eddie James <eajames@...ux.ibm.com>
---
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 a9cb355324d1..ffff8da707b8 100644
--- a/net/ncsi/ncsi-manage.c
+++ b/net/ncsi/ncsi-manage.c
@@ -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);
--
2.27.0
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