This is a note to let you know that I've just added the patch titled drm/panfrost: Fix a deadlock between the shrinker and madvise path to the 5.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-panfrost-fix-a-deadlock-between-the-shrinker-and-madvise-path.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 7d2d6d01293e6d9b42a6cb410be4158571f7fe9d Mon Sep 17 00:00:00 2001 From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> Date: Sun, 1 Nov 2020 18:40:16 +0100 Subject: drm/panfrost: Fix a deadlock between the shrinker and madvise path From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> commit 7d2d6d01293e6d9b42a6cb410be4158571f7fe9d upstream. panfrost_ioctl_madvise() and panfrost_gem_purge() acquire the mappings and shmem locks in different orders, thus leading to a potential the mappings lock first. Fixes: bdefca2d8dc0 ("drm/panfrost: Add the panfrost_gem_mapping concept") Cc: <stable@xxxxxxxxxxxxxxx> Cc: Christian Hewitt <christianshewitt@xxxxxxxxx> Reported-by: Christian Hewitt <christianshewitt@xxxxxxxxx> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> Reviewed-by: Steven Price <steven.price@xxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20201101174016.839110-1-boris.brezillon@xxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/panfrost/panfrost_gem.c | 4 +--- drivers/gpu/drm/panfrost/panfrost_gem.h | 2 +- drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c | 14 +++++++++++--- 3 files changed, 13 insertions(+), 7 deletions(-) --- a/drivers/gpu/drm/panfrost/panfrost_gem.c +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c @@ -105,14 +105,12 @@ void panfrost_gem_mapping_put(struct pan kref_put(&mapping->refcount, panfrost_gem_mapping_release); } -void panfrost_gem_teardown_mappings(struct panfrost_gem_object *bo) +void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo) { struct panfrost_gem_mapping *mapping; - mutex_lock(&bo->mappings.lock); list_for_each_entry(mapping, &bo->mappings.list, node) panfrost_gem_teardown_mapping(mapping); - mutex_unlock(&bo->mappings.lock); } int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_priv) --- a/drivers/gpu/drm/panfrost/panfrost_gem.h +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h @@ -82,7 +82,7 @@ struct panfrost_gem_mapping * panfrost_gem_mapping_get(struct panfrost_gem_object *bo, struct panfrost_file_priv *priv); void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping); -void panfrost_gem_teardown_mappings(struct panfrost_gem_object *bo); +void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo); void panfrost_gem_shrinker_init(struct drm_device *dev); void panfrost_gem_shrinker_cleanup(struct drm_device *dev); --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c +++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c @@ -40,18 +40,26 @@ static bool panfrost_gem_purge(struct dr { struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); struct panfrost_gem_object *bo = to_panfrost_bo(obj); + bool ret = false; if (atomic_read(&bo->gpu_usecount)) return false; - if (!mutex_trylock(&shmem->pages_lock)) + if (!mutex_trylock(&bo->mappings.lock)) return false; - panfrost_gem_teardown_mappings(bo); + if (!mutex_trylock(&shmem->pages_lock)) + goto unlock_mappings; + + panfrost_gem_teardown_mappings_locked(bo); drm_gem_shmem_purge_locked(obj); + ret = true; mutex_unlock(&shmem->pages_lock); - return true; + +unlock_mappings: + mutex_unlock(&bo->mappings.lock); + return ret; } static unsigned long Patches currently in stable-queue which might be from boris.brezillon@xxxxxxxxxxxxx are queue-5.9/drm-panfrost-fix-a-deadlock-between-the-shrinker-and-madvise-path.patch