netdev - Kernel hang caused by commit "can: m_can: Start/Cancel polling timer together with interrupts"

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Date: Tue, 18 Jun 2024 18:12:27 +0200
From: Matthias Schiffer <matthias.schiffer@...tq-group.com>
To: Markus Schneider-Pargmann <msp@...libre.com>
Cc: Chandrasekar Ramakrishnan <rcsekar@...sung.com>, Marc Kleine-Budde
 <mkl@...gutronix.de>, Vincent Mailhol <mailhol.vincent@...adoo.fr>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>,  Paolo Abeni <pabeni@...hat.com>, Tony Lindgren
 <tony@...mide.com>, Judith Mendez <jm@...com>,  linux-can@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,  linux@...tq-group.com
Subject: Kernel hang caused by commit "can: m_can: Start/Cancel polling
 timer together with interrupts"

Hi Markus,

we've found that recent kernels hang on the TI AM62x SoC (where no m_can interrupt is available and
thus the polling timer is used), always a few seconds after the CAN interfaces are set up.

I have bisected the issue to commit a163c5761019b ("can: m_can: Start/Cancel polling timer together
with interrupts"). Both master and 6.6 stable (which received a backport of the commit) are
affected. On 6.6 the commit is easy to revert, but on master a lot has happened on top of that
change.

As far as I can tell, the reason is that hrtimer_cancel() tries to cancel the timer synchronously,
which will deadlock when called from the hrtimer callback itself (hrtimer_callback -> m_can_isr ->
m_can_disable_all_interrupts -> hrtimer_cancel).

I can try to come up with a fix, but I think you are much more familiar with the driver code. Please
let me know if you need any more information.

Best regards,
Matthias

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