linux-kernel - [PATCH v3] can: slcan: do not sleep with a spin lock held

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Date:   Fri, 15 Jul 2022 09:29:51 +0200
From:   Dario Binacchi <dario.binacchi@...rulasolutions.com>
To:     linux-kernel@...r.kernel.org
Cc:     ltp@...ts.linux.it, Jeroen Hofstee <jhofstee@...tronenergy.com>,
        lkp@...el.com, Richard Palethorpe <rpalethorpe@...e.de>,
        kernel test robot <oliver.sang@...el.com>, lkp@...ts.01.org,
        Jiri Slaby <jirislaby@...nel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Dario Binacchi <dario.binacchi@...rulasolutions.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Paolo Abeni <pabeni@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH v3] can: slcan: do not sleep with a spin lock held

We can't call close_candev() with a spin lock held, so release the lock
before calling it. After calling close_candev(), we can update the
fields of the private `struct can_priv' without having to acquire the
lock.

Fixes: c4e54b063f42f ("can: slcan: use CAN network device driver API")
Reported-by: kernel test robot <oliver.sang@...el.com>
Link: https://lore.kernel.org/linux-kernel/Ysrf1Yc5DaRGN1WE@xsang-OptiPlex-9020/
Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>

---

Changes in v3:
- Update the commit message.
- Reset sl->rcount and sl->xleft before releasing the spin lock.

Changes in v2:
- Release the lock just before calling the close_candev().

 drivers/net/can/slcan/slcan-core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
index 54d29a410ad5..d40ddc596596 100644
--- a/drivers/net/can/slcan/slcan-core.c
+++ b/drivers/net/can/slcan/slcan-core.c
@@ -689,15 +689,14 @@ static int slc_close(struct net_device *dev)
 		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 	}
 	netif_stop_queue(dev);
+	sl->rcount   = 0;
+	sl->xleft    = 0;
+	spin_unlock_bh(&sl->lock);
 	close_candev(dev);
 	sl->can.state = CAN_STATE_STOPPED;
 	if (sl->can.bittiming.bitrate == CAN_BITRATE_UNKNOWN)
 		sl->can.bittiming.bitrate = CAN_BITRATE_UNSET;
 
-	sl->rcount   = 0;
-	sl->xleft    = 0;
-	spin_unlock_bh(&sl->lock);
-
 	return 0;
 }
 
-- 
2.32.0