drm/panfrost: Use mutex_trylock in panfrost_gem_purge (55b9a054) · Commits · 戴 / test

Lockdep reports a circular locking dependency with pages_lock taken in the shrinker callback. The deadlock can't actually happen with current users at least as a BO will never be purgeable when pages_lock is held. To be safe, let's use mutex_trylock() instead and bail if a BO is locked already. Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Signed-off-by:

Rob Herring <robh@kernel.org> Reviewed-by:

Steven Price <steven.price@arm.com> Acked-by:

Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190823021216.5862-7-robh@kernel.org

drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c

+7 −4

Original line number	Diff line number	Diff line
		@@ -36,15 +36,18 @@ panfrost_gem_shrinker_count(struct shrinker shrinker, struct shrink_control sc
		return count;
		}

		static void panfrost_gem_purge(struct drm_gem_object *obj)
		static bool panfrost_gem_purge(struct drm_gem_object *obj)
		{
		struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
		mutex_lock(&shmem->pages_lock);

		if (!mutex_trylock(&shmem->pages_lock))
		return false;

		panfrost_mmu_unmap(to_panfrost_bo(obj));
		drm_gem_shmem_purge_locked(obj);

		mutex_unlock(&shmem->pages_lock);
		return true;
		}

		static unsigned long
		@@ -61,8 +64,8 @@ panfrost_gem_shrinker_scan(struct shrinker shrinker, struct shrink_control sc)
		list_for_each_entry_safe(shmem, tmp, &pfdev->shrinker_list, madv_list) {
		if (freed >= sc->nr_to_scan)
		break;
		if (drm_gem_shmem_is_purgeable(shmem)) {
		panfrost_gem_purge(&shmem->base);
		if (drm_gem_shmem_is_purgeable(shmem) &&
		panfrost_gem_purge(&shmem->base)) {
		freed += shmem->base.size >> PAGE_SHIFT;
		list_del_init(&shmem->madv_list);
		}

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