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Message-Id: <4cf24d94ecf99d6feb4cb1ff7e01fb33976d9df0.1649310812.git.duoming@zju.edu.cn>
Date: Thu, 7 Apr 2022 14:37:00 +0800
From: Duoming Zhou <duoming@....edu.cn>
To: linux-kernel@...r.kernel.org
Cc: chris@...kel.net, jcmvbkbc@...il.com, mustafa.ismail@...el.com,
shiraz.saleem@...el.com, jgg@...pe.ca, wg@...ndegger.com,
mkl@...gutronix.de, davem@...emloft.net, kuba@...nel.org,
pabeni@...hat.com, jes@...ined-monkey.org,
gregkh@...uxfoundation.org, jirislaby@...nel.org,
alexander.deucher@....com, linux-xtensa@...ux-xtensa.org,
linux-rdma@...r.kernel.org, linux-can@...r.kernel.org,
netdev@...r.kernel.org, linux-hippi@...site.dk,
linux-staging@...ts.linux.dev, linux-serial@...r.kernel.org,
linux-usb@...r.kernel.org, Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH 08/11] drivers: net: can: Fix deadlock in grcan_close()
There are deadlocks caused by del_timer_sync(&priv->hang_timer)
and del_timer_sync(&priv->rr_timer) in grcan_close(), one of
the deadlocks are shown below:
(Thread 1) | (Thread 2)
| grcan_reset_timer()
grcan_close() | mod_timer()
spin_lock_irqsave() //(1) | (wait a time)
... | grcan_initiate_running_reset()
del_timer_sync() | spin_lock_irqsave() //(2)
(wait timer to stop) | ...
We hold priv->lock in position (1) of thread 1 and use
del_timer_sync() to wait timer to stop, but timer handler
also need priv->lock in position (2) of thread 2.
As a result, grcan_close() will block forever.
This patch extracts del_timer_sync() from the protection of
spin_lock_irqsave(), which could let timer handler to obtain
the needed lock.
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
drivers/net/can/grcan.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
index d0c5a7a60da..1189057b5d6 100644
--- a/drivers/net/can/grcan.c
+++ b/drivers/net/can/grcan.c
@@ -1102,8 +1102,10 @@ static int grcan_close(struct net_device *dev)
priv->closing = true;
if (priv->need_txbug_workaround) {
+ spin_unlock_irqrestore(&priv->lock, flags);
del_timer_sync(&priv->hang_timer);
del_timer_sync(&priv->rr_timer);
+ spin_lock_irqsave(&priv->lock, flags);
}
netif_stop_queue(dev);
grcan_stop_hardware(dev);
--
2.17.1
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