linux-kernel - Re: [PATCH v2] Revert "drm/nouveau: Remove waitque for sched teardown"

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Message-Id: <DCJHFF0AEDB6.6JMTQPQA5800@kernel.org>
Date: Wed, 03 Sep 2025 23:27:37 +0200
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Philipp Stanner" <phasta@...nel.org>
Cc: "Lyude Paul" <lyude@...hat.com>, "David Airlie" <airlied@...il.com>,
 "Simona Vetter" <simona@...ll.ch>, "Sumit Semwal"
 <sumit.semwal@...aro.org>, Christian König
 <christian.koenig@....com>, <dri-devel@...ts.freedesktop.org>,
 <nouveau@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] Revert "drm/nouveau: Remove waitque for sched
 teardown"

On Mon Sep 1, 2025 at 10:31 AM CEST, Philipp Stanner wrote:
> This reverts:
>
> commit bead88002227 ("drm/nouveau: Remove waitque for sched teardown")
> commit 5f46f5c7af8c ("drm/nouveau: Add new callback for scheduler teardown")
>
> from the drm/sched teardown leak fix series:
>
> https://lore.kernel.org/dri-devel/20250710125412.128476-2-phasta@kernel.org/
>
> The aforementioned series removed a blocking waitqueue from
> nouveau_sched_fini(). It was mistakenly assumed that this waitqueue only
> prevents jobs from leaking, which the series fixed.
>
> The waitqueue, however, also guarantees that all VM_BIND related jobs
> are finished in order, cleaning up mappings in the GPU's MMU. These jobs
> must be executed sequentially. Without the waitqueue, this is no longer
> guaranteed, because entity and scheduler teardown can race with each
> other.
>
> Revert all patches related to the waitqueue removal.
>
> Fixes: bead88002227 ("drm/nouveau: Remove waitque for sched teardown")
> Suggested-by: Danilo Krummrich <dakr@...nel.org>
> Signed-off-by: Philipp Stanner <phasta@...nel.org>

Applied to drm-misc-fixes, thanks!