Re: [PATCH] drm/panfrost: Fix leak when free gem object

[Steven Price <steven.price@arm.com>]

On 10/07/2025 04:05, lihongtao wrote:
> obj->mappings.lock should be destroyed when free
> panfrost gem object in panfrost_gem_free_object.

mutex_destroy() doesn't actually release any resources. It is purely a
debugging feature (if CONFIG_DEBUG_MUTEXES is disabled then it is
compiled away completely).

So it's not a "leak" as such. But there is some value in using it as it
would (in debug builds) warn us if we attempt to destroy a locked mutex
or attempt to use a mutex after the destroy.

But if we're going to fix this I think we should be more complete. A
quick grep should we have 6 different mutexes in panfrost:

panfrost_device.c:      mutex_init(&pfdev->sched_lock);
panfrost_device.c:      mutex_init(&pfdev->debugfs.gems_lock);
panfrost_drv.c: mutex_init(&pfdev->shrinker_lock);
panfrost_gem.c: mutex_init(&obj->mappings.lock);
panfrost_gem.c: mutex_init(&obj->label.lock);
panfrost_perfcnt.c:     mutex_init(&perfcnt->lock);

But there's only one existing call to mutex_destroy():

panfrost_gem.c: mutex_destroy(&bo->label.lock);

It would be good to consider if the other mutexes should also be destroyed.

Thanks,
Steve

> 
> Signed-off-by: lihongtao <lihongtao@kylinos.cn>
> ---
>  drivers/gpu/drm/panfrost/panfrost_gem.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index 963f04ba2de6..00549f482eec 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -49,6 +49,7 @@ static void panfrost_gem_free_object(struct drm_gem_object *obj)
>  		kvfree(bo->sgts);
>  	}
>  
> +	mutex_destroy(&bo->mappings.lock);
>  	drm_gem_shmem_free(&bo->base);
>  }
>