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Commit a8e83b17 authored by Tyler Hall's avatar Tyler Hall Committed by David S. Miller
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slcan: Port write_wakeup deadlock fix from slip 



The commit "slip: Fix deadlock in write_wakeup" fixes a deadlock caused
by a change made in both slcan and slip. This is a direct port of that
fix.

Signed-off-by: default avatarTyler Hall <tylerwhall@gmail.com>
Cc: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: Andre Naujoks <nautsch2@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 661f7fda

drivers/net/can/slcan.c

+27 −10
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ 
#include <linux/delay.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/workqueue.h>

#include <linux/can.h>

#include <linux/can/skb.h>
@@ -85,6 +86,7 @@ struct slcan { 
	struct tty_struct	*tty;		/* ptr to TTY structure	     */

	struct net_device	*dev;		/* easy for intr handling    */

	spinlock_t		lock;

	struct work_struct	tx_work;	/* Flushes transmit buffer   */



	/* These are pointers to the malloc()ed frame buffers. */

	unsigned char		rbuff[SLC_MTU];	/* receiver buffer	     */
@@ -309,36 +311,46 @@ static void slc_encaps(struct slcan *sl, struct can_frame *cf) 
	sl->dev->stats.tx_bytes += cf->can_dlc;

}



/*

 * Called by the driver when there's room for more data.  If we have

 * more packets to send, we send them here.

 */

static void slcan_write_wakeup(struct tty_struct *tty)

/* Write out any remaining transmit buffer. Scheduled when tty is writable */

static void slcan_transmit(struct work_struct *work)

{

	struct slcan *sl = container_of(work, struct slcan, tx_work);

	int actual;

	struct slcan *sl = (struct slcan *) tty->disc_data;



	spin_lock_bh(&sl->lock);

	/* First make sure we're connected. */

	if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))

	if (!sl->tty || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev)) {

		spin_unlock_bh(&sl->lock);

		return;

	}



	spin_lock_bh(&sl->lock);

	if (sl->xleft <= 0)  {

		/* Now serial buffer is almost free & we can start

		 * transmission of another packet */

		sl->dev->stats.tx_packets++;

		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);

		spin_unlock_bh(&sl->lock);

		netif_wake_queue(sl->dev);

		return;

	}



	actual = tty->ops->write(tty, sl->xhead, sl->xleft);

	actual = sl->tty->ops->write(sl->tty, sl->xhead, sl->xleft);

	sl->xleft -= actual;

	sl->xhead += actual;

	spin_unlock_bh(&sl->lock);

}



/*

 * Called by the driver when there's room for more data.

 * Schedule the transmit.

 */

static void slcan_write_wakeup(struct tty_struct *tty)

{

	struct slcan *sl = tty->disc_data;



	schedule_work(&sl->tx_work);

}



/* Send a can_frame to a TTY queue. */

static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)

{
@@ -528,6 +540,7 @@ static struct slcan *slc_alloc(dev_t line) 
	sl->magic = SLCAN_MAGIC;

	sl->dev	= dev;

	spin_lock_init(&sl->lock);

	INIT_WORK(&sl->tx_work, slcan_transmit);

	slcan_devs[i] = dev;



	return sl;
@@ -626,8 +639,12 @@ static void slcan_close(struct tty_struct *tty) 
	if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)

		return;



	spin_lock_bh(&sl->lock);

	tty->disc_data = NULL;

	sl->tty = NULL;

	spin_unlock_bh(&sl->lock);



	flush_work(&sl->tx_work);



	/* Flush network side */

	unregister_netdev(sl->dev);