On Tue, Nov 15, 2022 at 10:30:01AM +0100, Andrzej Hajda wrote: > On 13.07.2021 15:59, Daniel Vetter wrote: > > Some vague evidences suggests this can go wrong. Try to prevent it by > > holding the right mutex and clearing ->deferred_setup to make sure we > > later on don't accidentally try to re-register the fbdev when the > > driver thought it had it all cleaned up already. > > > > v2: I realized that this is fundamentally butchered, and CI complained > > about lockdep splats. So limit the critical section again and just add > > a few notes what the proper fix is. > > > > References: https://intel-gfx-ci.01.org/tree/linux-next/next-20201215/fi-byt-j1900/igt@i915_pm_rpm@xxxxxxxxxxxxxxxxxx > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > > Cc: Maxime Ripard <mripard@xxxxxxxxxx> > > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> > > Cc: David Airlie <airlied@xxxxxxxx> > > Cc: Daniel Vetter <daniel@xxxxxxxx> > > Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx> I just dropped this one from my patch pile a while ago, because there were conflicts. If you like it, feel free to resurrect&rebase and then merge it (but maybe cc intel-gfx so the CI there can test it). -Daniel > > Regards > Andrzej > > > --- > > drivers/gpu/drm/drm_fb_helper.c | 10 ++++++++++ > > 1 file changed, 10 insertions(+) > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > > index 9d82fda274eb..8f11e5abb222 100644 > > --- a/drivers/gpu/drm/drm_fb_helper.c > > +++ b/drivers/gpu/drm/drm_fb_helper.c > > @@ -598,6 +598,9 @@ EXPORT_SYMBOL(drm_fb_helper_alloc_fbi); > > * A wrapper around unregister_framebuffer, to release the fb_info > > * framebuffer device. This must be called before releasing all resources for > > * @fb_helper by calling drm_fb_helper_fini(). > > + * > > + * Note that this is fundamentally racy on hotunload because it doen't handle > > + * open fbdev file descriptors at all. Use drm_fbdev_generic_setup() instead. > > */ > > void drm_fb_helper_unregister_fbi(struct drm_fb_helper *fb_helper) > > { > > @@ -611,6 +614,9 @@ EXPORT_SYMBOL(drm_fb_helper_unregister_fbi); > > * @fb_helper: driver-allocated fbdev helper, can be NULL > > * > > * This cleans up all remaining resources associated with @fb_helper. > > + * > > + * Note that this is fundamentally racy on hotunload because it doen't handle > > + * open fbdev file descriptors at all. Use drm_fbdev_generic_setup() instead. > > */ > > void drm_fb_helper_fini(struct drm_fb_helper *fb_helper) > > { > > @@ -2382,6 +2388,10 @@ static void drm_fbdev_client_unregister(struct drm_client_dev *client) > > { > > struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client); > > + mutex_lock(&fb_helper->lock); > > + fb_helper->deferred_setup = false; > > + mutex_unlock(&fb_helper->lock); > > + > > if (fb_helper->fbdev) > > /* drm_fbdev_fb_destroy() takes care of cleanup */ > > drm_fb_helper_unregister_fbi(fb_helper); > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
