linux-kernel - Re: [PATCH 1/3] drm/amd: fix race in page flip job

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Message-ID: <02562071-6010-7c49-fb82-aceaf24d877f@daenzer.net>
Date:   Fri, 21 Dec 2018 09:56:52 +0100
From:   Michel Dänzer <michel@...nzer.net>
To:     Yu Zhao <yuzhao@...gle.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Christian König <christian.koenig@....com>,
        Alex Deucher <alexander.deucher@....com>
Cc:     David Zhou <David1.Zhou@....com>,
        Daniel Stone <daniels@...labora.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, Samuel Li <Samuel.Li@....com>,
        Junwei Zhang <Jerry.Zhang@....com>,
        Harry Wentland <harry.wentland@....com>
Subject: Re: [PATCH 1/3] drm/amd: fix race in page flip job

On 2018-12-21 4:10 a.m., Yu Zhao wrote:
> Fix race between page flip job submission and completion. We invoke
> page_flip callback to submit page flip job to GPU first and then set
> pflip_status. If GPU fires page flip done irq in between, its handler
> won't see the correct pflip_status thus will refuse to notify the job
> completion. The job will eventually times out.
> 
> Reverse the order of calling page_flip and setting pflip_status to
> fix the race.

There is no race, amdgpu_crtc->pflip_status is protected by dev->event_lock.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer