linux-kernel - Re: [PATCH v1 1/6] drm/lima: fix devfreq refcount imbalance for job timeouts

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Date: Fri, 19 Jan 2024 09:50:42 +0800
From: Qiang Yu <yuq825@...il.com>
To: Erico Nunes <nunes.erico@...il.com>
Cc: dri-devel@...ts.freedesktop.org, lima@...ts.freedesktop.org, 
	anarsoul@...il.com, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Sumit Semwal <sumit.semwal@...aro.org>, christian.koenig@....com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/6] drm/lima: fix devfreq refcount imbalance for job timeouts

On Thu, Jan 18, 2024 at 7:14 PM Erico Nunes <nunes.erico@...il.com> wrote:
>
> On Thu, Jan 18, 2024 at 2:36 AM Qiang Yu <yuq825@...il.com> wrote:
> >
> > So this is caused by same job trigger both done and timeout handling?
> > I think a better way to solve this is to make sure only one handler
> > (done or timeout) process the job instead of just making lima_pm_idle()
> > unique.
>
> It's not very clear to me how to best ensure that, with the drm_sched
> software timeout and the irq happening potentially at the same time.
This could be done by stopping scheduler run more job and disable
GP/PP interrupt. Then after sync irq, there should be no more new
irq gets in when we handling timeout.

> I think patch 4 in this series describes and covers the most common
> case that this would be hit. So maybe now this patch could be dropped
> in favour of just that one.
Yes.

> But since this was a bit hard to reproduce and I'm not sure the issue
> is entirely covered by that, I just decided to keep this small change
> as it prevented all the stack trace reproducers I was able to come up
> with.
>
> Erico