Hi Am 21.02.23 um 11:27 schrieb Javier Martinez Canillas:
Thomas Zimmermann <tzimmermann@xxxxxxx> 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.
Good point. After looking through the recent fbdev commits, I'll use commit 643231b28380 ("drm/fbdev-generic: Minimize hotplug error handling") for the tag. This is the one that added the call to drm_fb_helper_fini() to the client's hotplug handler. And _fini() currently does the _unprepare(), when it shouldn't.
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> Cc: Maxime Ripard <mripard@xxxxxxxxxx> Cc: David Airlie <airlied@xxxxxxxxx> Cc: Daniel Vetter <daniel@xxxxxxxx> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> ---The change itself looks good to me. Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Thanks a lot. Best regards Thomas -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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