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* [PATCH RFC] can: m_can: m_can_tx_work_queue(): fix tx_skb race condition
@ 2021-05-05 11:43 Marc Kleine-Budde
  2021-05-05 12:06 ` Torin Cooper-Bennun
  0 siblings, 1 reply; 5+ messages in thread
From: Marc Kleine-Budde @ 2021-05-05 11:43 UTC (permalink / raw)
  To: linux-can; +Cc: Marc Kleine-Budde

The m_can_start_xmit() function checks if the cdev->tx_skb is NULL and
returns with NETDEV_TX_BUSY in case tx_sbk is not NULL.

There is a race condition in the m_can_tx_work_queue(), where first
the skb is send to the driver and then the case tx_sbk is set to NULL.
A TX complete IRQ might come in between and wake the queue, which
results in tx_skb not being cleared yet.

Fixes: f524f829b75a ("can: m_can: Create a m_can platform framework")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
Hello,

compile time tested only.

Marc

 drivers/net/can/m_can/m_can.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 2fa10bc0befe..bba2a449ac70 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1544,6 +1544,8 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
 	int i;
 	int putidx;
 
+	cdev->tx_skb = NULL;
+
 	/* Generate ID field for TX buffer Element */
 	/* Common to all supported M_CAN versions */
 	if (cf->can_id & CAN_EFF_FLAG) {
@@ -1660,7 +1662,6 @@ static void m_can_tx_work_queue(struct work_struct *ws)
 						   tx_work);
 
 	m_can_tx_handler(cdev);
-	cdev->tx_skb = NULL;
 }
 
 static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
-- 
2.30.2



^ permalink raw reply related	[flat|nested] 5+ messages in thread

* Re: [PATCH RFC] can: m_can: m_can_tx_work_queue(): fix tx_skb race condition
  2021-05-05 11:43 [PATCH RFC] can: m_can: m_can_tx_work_queue(): fix tx_skb race condition Marc Kleine-Budde
@ 2021-05-05 12:06 ` Torin Cooper-Bennun
  2021-05-05 12:35   ` Marc Kleine-Budde
  0 siblings, 1 reply; 5+ messages in thread
From: Torin Cooper-Bennun @ 2021-05-05 12:06 UTC (permalink / raw)
  To: Marc Kleine-Budde; +Cc: linux-can

On Wed, May 05, 2021 at 01:43:02PM +0200, Marc Kleine-Budde wrote:
> The m_can_start_xmit() function checks if the cdev->tx_skb is NULL and
> returns with NETDEV_TX_BUSY in case tx_sbk is not NULL.
> 
> There is a race condition in the m_can_tx_work_queue(), where first
> the skb is send to the driver and then the case tx_sbk is set to NULL.
> A TX complete IRQ might come in between and wake the queue, which
> results in tx_skb not being cleared yet.
> 
> Fixes: f524f829b75a ("can: m_can: Create a m_can platform framework")
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> ---
> Hello,
> 
> compile time tested only.
> 
> Marc

Thanks a lot for spotting this Marc, after initial testing this is
working very well. I don't see that error message at all now, even at
very high transmit rates, and dropped frames are reduced considerably.

(Test setup: RPi CM4, TCAN4550, 500 kbit/s CAN-FD.)

--
Regards,

Torin Cooper-Bennun
Software Engineer | maxiluxsystems.com


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH RFC] can: m_can: m_can_tx_work_queue(): fix tx_skb race condition
  2021-05-05 12:06 ` Torin Cooper-Bennun
@ 2021-05-05 12:35   ` Marc Kleine-Budde
  2021-05-05 12:46     ` Torin Cooper-Bennun
  0 siblings, 1 reply; 5+ messages in thread
From: Marc Kleine-Budde @ 2021-05-05 12:35 UTC (permalink / raw)
  To: Torin Cooper-Bennun; +Cc: linux-can

[-- Attachment #1: Type: text/plain, Size: 1333 bytes --]

On 05.05.2021 13:06:59, Torin Cooper-Bennun wrote:
> On Wed, May 05, 2021 at 01:43:02PM +0200, Marc Kleine-Budde wrote:
> > The m_can_start_xmit() function checks if the cdev->tx_skb is NULL and
> > returns with NETDEV_TX_BUSY in case tx_sbk is not NULL.
> > 
> > There is a race condition in the m_can_tx_work_queue(), where first
> > the skb is send to the driver and then the case tx_sbk is set to NULL.
> > A TX complete IRQ might come in between and wake the queue, which
> > results in tx_skb not being cleared yet.
> > 
> > Fixes: f524f829b75a ("can: m_can: Create a m_can platform framework")
> > Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> > ---
> > Hello,
> > 
> > compile time tested only.
> > 
> > Marc
> 
> Thanks a lot for spotting this Marc, after initial testing this is
> working very well. I don't see that error message at all now, even at
> very high transmit rates, and dropped frames are reduced considerably.
> 
> (Test setup: RPi CM4, TCAN4550, 500 kbit/s CAN-FD.)

Can I add your Tested-by?

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH RFC] can: m_can: m_can_tx_work_queue(): fix tx_skb race condition
  2021-05-05 12:35   ` Marc Kleine-Budde
@ 2021-05-05 12:46     ` Torin Cooper-Bennun
  2021-05-05 12:50       ` Marc Kleine-Budde
  0 siblings, 1 reply; 5+ messages in thread
From: Torin Cooper-Bennun @ 2021-05-05 12:46 UTC (permalink / raw)
  To: Marc Kleine-Budde; +Cc: linux-can

On Wed, May 05, 2021 at 02:35:01PM +0200, Marc Kleine-Budde wrote:
> > Thanks a lot for spotting this Marc, after initial testing this is
> > working very well. I don't see that error message at all now, even at
> > very high transmit rates, and dropped frames are reduced considerably.
> > 
> > (Test setup: RPi CM4, TCAN4550, 500 kbit/s CAN-FD.)
> 
> Can I add your Tested-by?
> 
> Marc
> 
> -- 
> Pengutronix e.K.                 | Marc Kleine-Budde           |
> Embedded Linux                   | https://www.pengutronix.de  |
> Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
> Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

Yes, please do!

--
Regards,

Torin Cooper-Bennun
Software Engineer | maxiluxsystems.com


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH RFC] can: m_can: m_can_tx_work_queue(): fix tx_skb race condition
  2021-05-05 12:46     ` Torin Cooper-Bennun
@ 2021-05-05 12:50       ` Marc Kleine-Budde
  0 siblings, 0 replies; 5+ messages in thread
From: Marc Kleine-Budde @ 2021-05-05 12:50 UTC (permalink / raw)
  To: Torin Cooper-Bennun; +Cc: linux-can

[-- Attachment #1: Type: text/plain, Size: 773 bytes --]

On 05.05.2021 13:46:14, Torin Cooper-Bennun wrote:
> On Wed, May 05, 2021 at 02:35:01PM +0200, Marc Kleine-Budde wrote:
> > > Thanks a lot for spotting this Marc, after initial testing this is
> > > working very well. I don't see that error message at all now, even at
> > > very high transmit rates, and dropped frames are reduced considerably.
> > > 
> > > (Test setup: RPi CM4, TCAN4550, 500 kbit/s CAN-FD.)
> > 
> > Can I add your Tested-by?

> Yes, please do!

Done.

Thanks,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2021-05-05 12:50 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-05-05 11:43 [PATCH RFC] can: m_can: m_can_tx_work_queue(): fix tx_skb race condition Marc Kleine-Budde
2021-05-05 12:06 ` Torin Cooper-Bennun
2021-05-05 12:35   ` Marc Kleine-Budde
2021-05-05 12:46     ` Torin Cooper-Bennun
2021-05-05 12:50       ` Marc Kleine-Budde

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