On Thu, Jul 13, 2017 at 03:04:58PM +0100, Chris Wilson wrote: > Quoting Jiri Slaby (2017-07-13 14:57:31) > > Stealing this thread as an opensuse user hit that too: > > https://bugzilla.suse.com/show_bug.cgi?id=1045105 > > It's a false positive. I did once upon a time send some patches to move > the lockdep warning to kref so that didn't need to call it from drm > before an unlocked path. Basically you want > > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c > index 8dc11064253d..3118aed844f1 100644 > --- a/drivers/gpu/drm/drm_gem.c > +++ b/drivers/gpu/drm/drm_gem.c > @@ -826,7 +826,6 @@ drm_gem_object_put_unlocked(struct drm_gem_object *obj) > return; > > dev = obj->dev; > - might_lock(&dev->struct_mutex); > > if (dev->driver->gem_free_object_unlocked) > kref_put(&obj->refcount, drm_gem_object_free); > diff --git a/include/linux/kref.h b/include/linux/kref.h > index 29220724bf1c..4b1133cd5d20 100644 > --- a/include/linux/kref.h > +++ b/include/linux/kref.h > @@ -77,6 +77,8 @@ static inline int kref_put_mutex(struct kref *kref, > void (*release)(struct kref *kref), > struct mutex *lock) > { > + might_lock(lock); > + > if (refcount_dec_and_mutex_lock(&kref->refcount, lock)) { > release(kref); > return 1; > > > Though now we probably want to move that might_lock() into refcount. I think we want this here: diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 8dc11064253d..9663a79dd363 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -826,13 +826,15 @@ drm_gem_object_put_unlocked(struct drm_gem_object *obj) return; dev = obj->dev; - might_lock(&dev->struct_mutex); if (dev->driver->gem_free_object_unlocked) kref_put(&obj->refcount, drm_gem_object_free); - else if (kref_put_mutex(&obj->refcount, drm_gem_object_free, + else { + might_lock(&dev->struct_mutex); + if (kref_put_mutex(&obj->refcount, drm_gem_object_free, &dev->struct_mutex)) - mutex_unlock(&dev->struct_mutex); + mutex_unlock(&dev->struct_mutex); + } } EXPORT_SYMBOL(drm_gem_object_put_unlocked); If it works I'll wrap it into a patch. Note you need rather new-ish kernel to make sure we're sufficiently struct_mutex free in i915 (otherwise there's still the locking loop). v4.10 should be new enough afaics. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
