From: Sudeep Holla <sudeep.holla@arm.com>
To: jassisinghbrar@gmail.com
Cc: khilman@baylibre.com, linux-kernel@vger.kernel.org,
Jassi Brar <jaswinder.singh@linaro.org>,
Sudeep Holla <sudeep.holla@arm.com>,
linux-amlogic@lists.infradead.org, ionela.voinescu@arm.com,
da@libre.computer, jbrunet@baylibre.com
Subject: Re: [PATCH] mailbox: avoid timer start from callback
Date: Fri, 16 Oct 2020 18:50:39 +0100 [thread overview]
Message-ID: <20201016175039.7xs4cafoe2uq7zus@bogus> (raw)
In-Reply-To: <20201016173020.12686-1-jassisinghbrar@gmail.com>
On Fri, Oct 16, 2020 at 12:30:20PM -0500, jassisinghbrar@gmail.com wrote:
> From: Jassi Brar <jaswinder.singh@linaro.org>
>
> If the txdone is done by polling, it is possible for msg_submit() to start
> the timer while txdone_hrtimer() callback is running. If the timer needs
> recheduling, it could already be enqueued by the time hrtimer_forward_now()
> is called, leading hrtimer to loudly complain.
>
> WARNING: CPU: 3 PID: 74 at kernel/time/hrtimer.c:932 hrtimer_forward+0xc4/0x110
> CPU: 3 PID: 74 Comm: kworker/u8:1 Not tainted 5.9.0-rc2-00236-gd3520067d01c-dirty #5
> Hardware name: Libre Computer AML-S805X-AC (DT)
> Workqueue: events_freezable_power_ thermal_zone_device_check
> pstate: 20000085 (nzCv daIf -PAN -UAO BTYPE=--)
> pc : hrtimer_forward+0xc4/0x110
> lr : txdone_hrtimer+0xf8/0x118
> [...]
>
> This can be fixed by not starting the timer from the callback path. Which
> requires the timer reloading as long as any message is queued on the
> channel, and not just when current tx is not done yet.
>
I came to similar conclusion and was testing something similar. You bet
me. Since we have single timer and multiple channels, each time a message
is enqueued on any channel, timer gets added which is wrong.
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
I tested this patch too by reverting offending commit in -next, so
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
You seem to have dropped the Fixes tags. Is that intentional ? If so,
any particular reasons. I think it is stable material and better to have
fixes tag so that it gets added to stable trees.
--
Regards,
Sudeep
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next prev parent reply other threads:[~2020-10-16 17:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-16 17:30 [PATCH] mailbox: avoid timer start from callback jassisinghbrar
2020-10-16 17:50 ` Sudeep Holla [this message]
2020-10-16 18:24 ` Jassi Brar
2020-10-16 18:38 ` Jerome Brunet
2020-10-16 18:45 ` Jassi Brar
2020-10-16 19:32 ` Jerome Brunet
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