linux-kernel - Re: [PATCH 1/2] drm: introduce page_flip

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Message-ID: <CAFZQkGz54fuprfAwT1BiadfrqJu7PWHNmFGkFzAYacVqPq-vZA@mail.gmail.com>
Date: Thu, 29 Jan 2026 22:56:52 +0100
From: Xaver Hugl <xaver.hugl@....org>
To: Michel Dänzer <michel.daenzer@...lbox.org>
Cc: Christian König <christian.koenig@....com>, 
	Timur Kristóf <timur.kristof@...il.com>, 
	Alex Deucher <alexdeucher@...il.com>, Hamza Mahfooz <someguy@...ective-light.com>, 
	Mario Limonciello <mario.limonciello@....com>, dri-devel@...ts.freedesktop.org, 
	Alex Deucher <alexander.deucher@....com>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>, 
	Rodrigo Siqueira <siqueira@...lia.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Sunil Khatri <sunil.khatri@....com>, Ce Sun <cesun102@....com>, Lijo Lazar <lijo.lazar@....com>, 
	Kenneth Feng <kenneth.feng@....com>, Ivan Lipski <ivan.lipski@....com>, 
	Alex Hung <alex.hung@....com>, Tom Chung <chiahsuan.chung@....com>, 
	Melissa Wen <mwen@...lia.com>, Fangzhi Zuo <Jerry.Zuo@....com>, amd-gfx@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] drm: introduce page_flip_timeout()

> Another possibility is that test-only commits with the DRM_MODE_ATOMIC_TEST_ONLY flag (which can happen in parallel while the kernel is processing a "real" commit) accidentally have side effects on the current kernel state, resulting in the "real" commit failing to do something it should. There have been bugs like that in the amdgpu DM code before.

Some users reported that GPU resets on dGPUs happens way less often
with legacy modesetting than atomic, which led me to the same
conclusion of possibly missing locks in the driver.
To test that theory, I recently gave some affected users a patch to
lock KWin's commit thread(s) while doing atomic tests on the main
thread, so it never does two atomic commits simultaneously.

Testing on APUs showed that it did not help there, but as I haven't
heard back from any dGPU users yet, it's still a possible factor.

- Xaver