Hi Daniel, On Tue, Jul 13, 2021 at 03:59:22PM +0200, 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> > --- > 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 s/doen't/doesn't/ > + * 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 s/doen't/doesn't/ > + * 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); I could not find any better spot to clear deferred_setup - so I think this is OK. With the two spellign issues fixed: Acked-by: Sam Ravnborg <sam@xxxxxxxxxxxx> No r-b as I an not too fluent in these code paths and all the locking. Sam _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
