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Message-ID: <ZO-BkaGuVCgdr3wc@slm.duckdns.org>
Date: Wed, 30 Aug 2023 07:51:13 -1000
From: Tejun Heo <tj@...nel.org>
To: Heiner Kallweit <hkallweit1@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
intel-gfx@...ts.freedesktop.org
Subject: Re: WQ_UNBOUND warning since recent workqueue refactoring
Hello,
(cc'ing i915 folks)
On Wed, Aug 30, 2023 at 04:57:42PM +0200, Heiner Kallweit wrote:
> Recently I started to see the following warning on linux-next and presumably
> this may be related to the refactoring of the workqueue core code.
>
> [ 56.900223] workqueue: output_poll_execute [drm_kms_helper] hogged CPU for >10000us 4 times, consider switching to WQ_UNBOUND
> [ 56.923226] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for >10000us 4 times, consider switching to WQ_UNBOUND
> [ 97.860430] workqueue: output_poll_execute [drm_kms_helper] hogged CPU for >10000us 8 times, consider switching to WQ_UNBOUND
> [ 97.884453] workqueue: i915_hpd_poll_init_work [i915] hogged CPU for >10000us 8 times, consider switching to WQ_UNBOUND
>
> Adding WQ_UNBOUND to these queues didn't change the behavior.
That should have made them go away as the code path isn't active at all for
WQ_UNBOUND workqueues. Can you please double check?
> Maybe relevant: I run the affected system headless.
i915 folks, workqueue recently added debug warnings which trigger when a
per-cpu work item hogs the CPU for too long - 10ms in this case. This is
problematic because such work item can stall other per-cpu work items.
* Is it expected for the above two work functions to occupy the CPU for over
10ms repeatedly?
* If so, can we make them use an unbound workqueue instead?
Thanks.
--
tejun
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