From: Oliver Hartkopp <socketcan@hartkopp•net>
To: Andre Naujoks <nautsch2@gmail•com>
Cc: davem@davemloft•net, Wolfgang Grandegger <wg@grandegger•com>,
Marc Kleine-Budde <mkl@pengutronix•de>,
linux-can@vger•kernel.org, netdev@vger•kernel.org,
linux-kernel@vger•kernel.org
Subject: Re: [PATCH net 1/3] slip/slcan: added locking in wakeup function
Date: Fri, 13 Sep 2013 20:45:29 +0200 [thread overview]
Message-ID: <52335D49.1000105@hartkopp.net> (raw)
In-Reply-To: <1379093833-4949-2-git-send-email-nautsch2@gmail.com>
On 13.09.2013 19:37, Andre Naujoks wrote:
> The locking is needed, since the the internal buffer for the CAN frames is
> changed during the wakeup call. This could cause buffer inconsistencies
> under high loads, especially for the outgoing short CAN packet skbuffs.
>
> The needed locks led to deadlocks before commit
> "5ede52538ee2b2202d9dff5b06c33bfde421e6e4 tty: Remove extra wakeup from pty
> write() path", which removed the direct callback to the wakeup function from the
> tty layer.
>
> As slcan.c is based on slip.c the issue in the original code is fixed, too.
>
> Signed-off-by: Andre Naujoks <nautsch2@gmail•com>
At least for slcan.c:
Acked-by: Oliver Hartkopp <socketcan@hartkopp•net>
Tnx for figuring that out with your heavy load testing.
Best regards,
Oliver
> ---
> drivers/net/can/slcan.c | 3 +++
> drivers/net/slip/slip.c | 3 +++
> 2 files changed, 6 insertions(+)
>
> diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
> index 874188b..d571e2e 100644
> --- a/drivers/net/can/slcan.c
> +++ b/drivers/net/can/slcan.c
> @@ -286,11 +286,13 @@ static void slcan_write_wakeup(struct tty_struct *tty)
> if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
> return;
>
> + spin_lock(&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);
> + spin_unlock(&sl->lock);
> netif_wake_queue(sl->dev);
> return;
> }
> @@ -298,6 +300,7 @@ static void slcan_write_wakeup(struct tty_struct *tty)
> actual = tty->ops->write(tty, sl->xhead, sl->xleft);
> sl->xleft -= actual;
> sl->xhead += actual;
> + spin_unlock(&sl->lock);
> }
>
> /* Send a can_frame to a TTY queue. */
> diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
> index a34d6bf..cc70ecf 100644
> --- a/drivers/net/slip/slip.c
> +++ b/drivers/net/slip/slip.c
> @@ -429,11 +429,13 @@ static void slip_write_wakeup(struct tty_struct *tty)
> if (!sl || sl->magic != SLIP_MAGIC || !netif_running(sl->dev))
> return;
>
> + spin_lock(&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);
> + spin_unlock(&sl->lock);
> sl_unlock(sl);
> return;
> }
> @@ -441,6 +443,7 @@ static void slip_write_wakeup(struct tty_struct *tty)
> actual = tty->ops->write(tty, sl->xhead, sl->xleft);
> sl->xleft -= actual;
> sl->xhead += actual;
> + spin_unlock(&sl->lock);
> }
>
> static void sl_tx_timeout(struct net_device *dev)
>
next prev parent reply other threads:[~2013-09-13 18:45 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-13 17:37 [PATCH net 0/3] SLCAN/SLIP fixes and performance Andre Naujoks
2013-09-13 17:37 ` [PATCH net 1/3] slip/slcan: added locking in wakeup function Andre Naujoks
2013-09-13 18:45 ` Oliver Hartkopp [this message]
2013-09-19 9:36 ` Marc Kleine-Budde
2013-09-19 10:29 ` Andre Naujoks
2013-09-19 10:35 ` Marc Kleine-Budde
2013-09-19 10:43 ` Peter Hurley
2013-09-13 17:37 ` [PATCH net 2/3] lib: introduce upper case hex ascii helpers Andre Naujoks
2013-09-15 4:27 ` Thiago Farina
2013-09-15 4:35 ` Andrew Morton
2013-09-19 9:38 ` Marc Kleine-Budde
2013-09-19 9:57 ` Oliver Hartkopp
2013-09-13 17:37 ` [PATCH net 3/3] slcan: rewrite of slc_bump and slc_encaps Andre Naujoks
2013-09-13 18:43 ` Oliver Hartkopp
2013-09-19 9:47 ` Marc Kleine-Budde
2013-09-14 10:45 ` [PATCH net 0/3] SLCAN/SLIP fixes and performance Marc Kleine-Budde
2013-09-14 11:22 ` Andre Naujoks
2013-09-20 19:39 ` David Miller
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