On 23/08/2019 03:12, Rob Herring wrote:
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: Steven Price steven.price@arm.com Cc: Alyssa Rosenzweig alyssa.rosenzweig@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
v2: new patch
drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c index d191632b6197..458f0fa68111 100644 --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c +++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c @@ -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);