From mboxrd@z Thu Jan  1 00:00:00 1970
From: Maxime Ripard <maxime.ripard@bootlin.com>
Subject: Re: [PATCH v2 02/12] drm/fb-helper: Avoid race with DRM
 userspace
Date: Tue, 16 Apr 2019 11:26:48 +0200
Message-ID: <20190416092648.ha5x4yvatgmcizql@flea>
References: <20190407165243.54043-1-noralf@tronnes.org>
 <20190407165243.54043-3-noralf@tronnes.org>
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To: Noralf =?utf-8?Q?Tr=C3=B8nnes?= <noralf@tronnes.org>
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On Sun, Apr 07, 2019 at 06:52:33PM +0200, Noralf Tr=F8nnes wrote:
> drm_fb_helper_is_bound() is used to check if DRM userspace is in control.
> This is done by looking at the fb on the primary plane. By the time
> fb-helper gets around to committing, it's possible that the facts have
> changed.
>
> Avoid this race by holding the drm_device->master_mutex lock while
> committing. When DRM userspace does its first open, it will now wait
> until fb-helper is done. The helper will stay away if there's a master.
>
> Locking rule: Always take the fb-helper lock first.
>
> v2:
> - Remove drm_fb_helper_is_bound() (Daniel Vetter)
> - No need to check fb_helper->dev->master in
>   drm_fb_helper_single_fb_probe(), restore_fbdev_mode() has the check.
>
> Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Noralf Tr=F8nnes <noralf@tronnes.org>

With the changes asked by Daniel,
Reviewed-by: Maxime Ripard <maxime.ripard@bootlin.com>

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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