Commit 7d2d6d01 authored by Boris Brezillon's avatar Boris Brezillon
Browse files

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



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: bdefca2d ("drm/panfrost: Add the panfrost_gem_mapping concept")
Cc: <stable@vger.kernel.org>
Cc: Christian Hewitt <christianshewitt@gmail.com>
Reported-by: default avatarChristian Hewitt <christianshewitt@gmail.com>
Signed-off-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201101174016.839110-1-boris.brezillon@collabora.com
parent dcda7c28

drivers/gpu/drm/panfrost/panfrost_gem.c

+1 −3
Original line number Diff line number Diff line
@@ -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)

drivers/gpu/drm/panfrost/panfrost_gem.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c

+11 −3
Original line number Diff line number Diff line
@@ -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

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