From: Javier Martinez Canillas <javierm@redhat.com>
To: Thomas Zimmermann <tzimmermann@suse.de>,
airlied@gmail.com, daniel@ffwll.ch,
maarten.lankhorst@linux.intel.com, mripard@kernel.org
Cc: dri-devel@lists.freedesktop.org,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org,
intel-gfx@lists.freedesktop.org, linux-arm-msm@vger.kernel.org,
freedreno@lists.freedesktop.org, amd-gfx@lists.freedesktop.org,
linux-tegra@vger.kernel.org,
Thomas Zimmermann <tzimmermann@suse.de>
Subject: Re: [PATCH] drm/fb-helper: Remove drm_fb_helper_unprepare() from drm_fb_helper_fini()
Date: Tue, 21 Feb 2023 11:27:00 +0100 [thread overview]
Message-ID: <87y1orxqiz.fsf@minerva.mail-host-address-is-not-set> (raw)
In-Reply-To: <20230216140620.17699-1-tzimmermann@suse.de>
Thomas Zimmermann <tzimmermann@suse.de> writes:
> Move drm_fb_helper_unprepare() from drm_fb_helper_fini() into the
> calling fbdev implementation. Avoids a possible stale mutex with
> generic fbdev code.
>
> As indicated by its name, drm_fb_helper_prepare() prepares struct
> drm_fb_helper before setting up the fbdev support with a call to
> drm_fb_helper_init(). In legacy fbdev emulation, this happens next
> to each other. If successful, drm_fb_helper_fini() later tear down
> the fbdev device and also unprepare via drm_fb_helper_unprepare().
>
> Generic fbdev emulation prepares struct drm_fb_helper immediately
> after allocating the instance. It only calls drm_fb_helper_init()
> as part of processing a hotplug event. If the hotplug-handling fails,
> it runs drm_fb_helper_fini(). This unprepares the fb-helper instance
> and the next hotplug event runs on stale data.
>
> Solve this by moving drm_fb_helper_unprepare() from drm_fb_helper_fini()
> into the fbdev implementations. Call it right before freeing the
> fb-helper instance.
>
> Fixes: 4825797c36da ("drm/fb-helper: Introduce drm_fb_helper_unprepare()")
I think this should be Fixes: 032116bbe152 ("drm/fbdev-generic: Minimize
client unregistering") instead? Because commit 4825797c36da just added a
wrapper function for mutex_destroy(&fb_helper->lock), but it was commit
032116bbe152 that made drm_fbdev_cleanup() to call that helper function.
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: Javier Martinez Canillas <javierm@redhat.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: dri-devel@lists.freedesktop.org
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
The change itself looks good to me.
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
--
Best regards,
Javier Martinez Canillas
Core Platforms
Red Hat
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next prev parent reply other threads:[~2023-02-21 10:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-16 14:06 [PATCH] drm/fb-helper: Remove drm_fb_helper_unprepare() from drm_fb_helper_fini() Thomas Zimmermann
2023-02-16 20:11 ` Daniel Vetter
2023-02-17 8:18 ` Thomas Zimmermann
2023-02-17 19:48 ` Daniel Vetter
2023-02-21 10:27 ` Javier Martinez Canillas [this message]
2023-02-21 12:23 ` Thomas Zimmermann
2023-02-21 12:31 ` Javier Martinez Canillas
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