On Mon, 30 Oct 2023 02:01:58 +0300 Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> wrote: > @@ -238,6 +308,20 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem) > if (refcount_dec_not_one(&shmem->pages_use_count)) > return; > > + /* > + * Destroying the object is a special case because acquiring > + * the obj lock can cause a locking order inversion between > + * reservation_ww_class_mutex and fs_reclaim. > + * > + * This deadlock is not actually possible, because no one should > + * be already holding the lock when GEM is released. Unfortunately > + * lockdep is not aware of this detail. So when the refcount drops > + * to zero, we pretend it is already locked. > + */ > + if (!kref_read(&shmem->base.refcount) && > + refcount_dec_and_test(&shmem->pages_use_count)) > + return drm_gem_shmem_free_pages(shmem); Uh, with get/put_pages() being moved to the create/free_gem() hooks, we're back to a situation where pages_use_count > 0 when we reach gem->refcount == 0, which is not nice. We really need to patch drivers so they dissociate GEM creation from the backing storage allocation/reservation + mapping of the BO in GPU VM space.
