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drm/panfrost: Fix a deadlock between the shrinker and madvise path 

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@vger.kernel.org>
Cc: Christian Hewitt <christianshewitt@gmail.com>
Reported-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201101174016.839110-1-boris.brezillon@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Boris Brezillon 2020-11-01 18:40:16 +01:00 committed by Greg Kroah-Hartman
parent b9d91fa921
commit d61edc0600
3 changed files with 13 additions and 7 deletions
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4
drivers/gpu/drm/panfrost/panfrost_gem.c
View File

@ -105,14 +105,12 @@ void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping)
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)

2
drivers/gpu/drm/panfrost/panfrost_gem.h
View File

@ -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);

14
drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
View File

@ -40,18 +40,26 @@ static bool panfrost_gem_purge(struct drm_gem_object *obj)
{
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