From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: "Sebastian Würl" <sebastian.wuerl@ororatech.com>
Cc: "Wolfgang Grandegger" <wg@grandegger.com>,
"Marc Kleine-Budde" <mkl@pengutronix.de>,
"David S. Miller" <davem@davemloft.net>,
"Eric Dumazet" <edumazet@google.com>,
"Jakub Kicinski" <kuba@kernel.org>,
"Paolo Abeni" <pabeni@redhat.com>,
"Vincent Mailhol" <mailhol.vincent@wanadoo.fr>,
"Stefan Mätje" <stefan.maetje@esd.eu>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
"Oliver Hartkopp" <socketcan@hartkopp.net>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
linux-can@vger.kernel.org, netdev <netdev@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drivers/net/can/spi/mcp251x.c: Fix race condition on receive interrupt
Date: Wed, 3 Aug 2022 18:48:57 +0200 [thread overview]
Message-ID: <CAHp75VdCH2tJQq3v_-iNP27oWFGF7EtKc-w299tLhDV85WbroQ@mail.gmail.com> (raw)
In-Reply-To: <20220803153300.58732-1-sebastian.wuerl@ororatech.com>
On Wed, Aug 3, 2022 at 5:36 PM Sebastian Würl
<sebastian.wuerl@ororatech.com> wrote:
>
> The mcp251x driver uses both receiving mailboxes of the can controller
CAN
> chips. For retrieving the CAN frames from the controller via SPI, it checks
> once per interrupt which mailboxes have been filled, an will retrieve the
> messages accordingly.
>
> This introduces a race condition, as another CAN frame can enter mailbox 1
> while mailbox 0 is emptied. If now another CAN frame enters mailbox 0 until
> the interrupt handler is called next, mailbox 0 is emptied before
> mailbox 1, leading to out-of-order CAN frames in the network device.
>
> This is fixed by checking the interrupt flags once again after freeing
> mailbox 0, to correctly also empty mailbox 1 before leaving the handler.
>
> For reproducing the bug I created the following setup:
> - Two CAN devices, one Raspberry Pi with MCP2515, the other can be any.
> - Setup CAN to 1 MHz
> - Spam bursts of 5 CAN-messages with increasing CAN-ids
> - Continue sending the bursts while sleeping a second between the bursts
> - Check on the RPi whether the received messages have increasing CAN-ids
> - Without this patch, every burst of messages will contain a flipped pair
Fixes tag?
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2022-08-03 16:49 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-03 15:32 [PATCH] drivers/net/can/spi/mcp251x.c: Fix race condition on receive interrupt Sebastian Würl
2022-08-03 16:48 ` Andy Shevchenko [this message]
2022-08-03 16:50 ` Andy Shevchenko
2022-08-03 19:08 ` Marc Kleine-Budde
2022-08-03 18:59 ` Marc Kleine-Budde
2022-08-04 6:48 ` [PATCH] can: mcp251x: " Sebastian Würl
2022-08-04 7:06 ` Marc Kleine-Budde
2022-08-04 7:45 ` Sebastian Würl
2022-08-04 7:51 ` Marc Kleine-Budde
2022-08-04 7:59 ` [PATCH v3] " Sebastian Würl
2022-08-04 8:14 ` [PATCH v4] " Sebastian Würl
2022-08-04 8:28 ` Marc Kleine-Budde
2022-08-04 18:42 ` Andy Shevchenko
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