[Linaro-mm-sig] Re: [PATCH] drm/gem: modernize locks to use scoped_guard()

On Tue, Jun 16, 2026 at 11:49:57PM +0530, Biren Pandya wrote:

Several GEM core functions manually managed mutex_lock() and mutex_unlock() over single scopes or error paths. This adds boilerplate and carries the risk of lock leaks if error paths are refactored.

Modernize these locks by deploying the <linux/cleanup.h> scoped_guard() macro. This ensures that the locks are reliably dropped when the block exits, cleanly removing goto out_unlock paths and tightening the lifecycle.

What's the reason for doing so in in drm_gem and not other areas in DRM ?

Signed-off-by: Biren Pandya birenpandya@gmail.com

Compiled locally, but requires IGT validation by the DRM CI.

drivers/gpu/drm/drm_gem.c | 66 ++++++++++++++++++--------------------- 1 file changed, 30 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 891c3bff5ae0..d3a061d42ba7 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -346,13 +346,13 @@ void drm_gem_object_handle_put_unlocked(struct drm_gem_object *obj) * we checked for a name. */

• mutex_lock(&dev->object_name_lock);
• if (--obj->handle_count == 0) {

• drm_gem_object_handle_free(obj);
  

• drm_gem_object_exported_dma_buf_free(obj);
  

• final = true;
  

• scoped_guard(mutex, &dev->object_name_lock) {

• if (--obj->handle_count == 0) {
  

• 	drm_gem_object_handle_free(obj);
  

• 	drm_gem_object_exported_dma_buf_free(obj);
  

• 	final = true;
  

• }
  

  }

• mutex_unlock(&dev->object_name_lock);

if (final) drm_gem_object_put(obj); @@ -374,11 +374,8 @@ drm_gem_object_release_handle(int id, void *ptr, void *data) if (obj->funcs->close) obj->funcs->close(obj, file_priv);

• mutex_lock(&file_priv->prime.lock);
• drm_prime_remove_buf_handle(&file_priv->prime, id);
• mutex_unlock(&file_priv->prime.lock);

• scoped_guard(mutex, &file_priv->prime.lock)

• drm_prime_remove_buf_handle(&file_priv->prime, id);
  

drm_vma_node_revoke(&obj->vma_node, file_priv); @@ -1021,37 +1018,34 @@ int drm_gem_change_handle_ioctl(struct drm_device *dev, void *data, goto out; }

• mutex_lock(&file_priv->prime.lock);

• scoped_guard(mutex, &file_priv->prime.lock) {

• spin_lock(&file_priv->table_lock);
  

• ret = idr_alloc(&file_priv->object_idr, obj, handle, handle + 1,
  

• 		GFP_NOWAIT);
  

• spin_unlock(&file_priv->table_lock);
  

And why don't you use guards for the spinlock as well ?

• spin_lock(&file_priv->table_lock);
• ret = idr_alloc(&file_priv->object_idr, obj, handle, handle + 1,

• 	GFP_NOWAIT);
  

• spin_unlock(&file_priv->table_lock);

• if (ret < 0)
  

• 	break;
  

• if (ret < 0)

• goto out_unlock;
  

• if (obj->dma_buf) {
  

• 	ret = drm_prime_add_buf_handle(&file_priv->prime, obj->dma_buf,
  

• 				       handle);
  

• 	if (ret < 0) {
  

• 		spin_lock(&file_priv->table_lock);
  

• 		idr_remove(&file_priv->object_idr, handle);
  

• 		spin_unlock(&file_priv->table_lock);
  

• 		break;
  

• 	}
  

• if (obj->dma_buf) {

• ret = drm_prime_add_buf_handle(&file_priv->prime, obj->dma_buf,
  

• 			       handle);
  

• if (ret < 0) {
  

• 	spin_lock(&file_priv->table_lock);
  

• 	idr_remove(&file_priv->object_idr, handle);
  

• 	spin_unlock(&file_priv->table_lock);
  

• 	goto out_unlock;
  

• 	drm_prime_remove_buf_handle(&file_priv->prime, args->handle);
  

  }

• drm_prime_remove_buf_handle(&file_priv->prime, args->handle);
  

• }
• ret = 0;
• spin_lock(&file_priv->table_lock);
• idr_remove(&file_priv->object_idr, args->handle);
• spin_unlock(&file_priv->table_lock);

• ret = 0;
  

-out_unlock:

• mutex_unlock(&file_priv->prime.lock);

• spin_lock(&file_priv->table_lock);
  

• idr_remove(&file_priv->object_idr, args->handle);
  

• spin_unlock(&file_priv->table_lock);
  

• }

out: drm_gem_object_put(obj);

base-commit: 72c25183cac9bc584c9de21797a5883af44bcc7a