linux-kernel - Re: [PATCH v19 03/30] drm/gem: Document locking rule of vmap and evict callbacks

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Date: Thu, 25 Jan 2024 08:55:02 +0100
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc: David Airlie <airlied@...il.com>, Gerd Hoffmann <kraxel@...hat.com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, Christian König
 <christian.koenig@....com>, Qiang Yu <yuq825@...il.com>, Steven Price
 <steven.price@....com>, Emma Anholt <emma@...olt.net>, Melissa Wen
 <mwen@...lia.com>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, kernel@...labora.com,
 virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v19 03/30] drm/gem: Document locking rule of vmap and
 evict callbacks

On Fri,  5 Jan 2024 21:45:57 +0300
Dmitry Osipenko <dmitry.osipenko@...labora.com> wrote:

> The vmap/vunmap/evict GEM callbacks are always invoked with a held GEM's
> reservation lock. Document this locking rule for clarity.
> 
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>

> ---
>  include/drm/drm_gem.h | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index f835fdee6a5e..021f64371056 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -156,7 +156,8 @@ struct drm_gem_object_funcs {
>  	 * @vmap:
>  	 *
>  	 * Returns a virtual address for the buffer. Used by the
> -	 * drm_gem_dmabuf_vmap() helper.
> +	 * drm_gem_dmabuf_vmap() helper. Called with a held GEM reservation
> +	 * lock.
>  	 *
>  	 * This callback is optional.
>  	 */
> @@ -166,7 +167,8 @@ struct drm_gem_object_funcs {
>  	 * @vunmap:
>  	 *
>  	 * Releases the address previously returned by @vmap. Used by the
> -	 * drm_gem_dmabuf_vunmap() helper.
> +	 * drm_gem_dmabuf_vunmap() helper. Called with a held GEM reservation
> +	 * lock.
>  	 *
>  	 * This callback is optional.
>  	 */
> @@ -189,7 +191,8 @@ struct drm_gem_object_funcs {
>  	 * @evict:
>  	 *
>  	 * Evicts gem object out from memory. Used by the drm_gem_object_evict()
> -	 * helper. Returns 0 on success, -errno otherwise.
> +	 * helper. Returns 0 on success, -errno otherwise. Called with a held
> +	 * GEM reservation lock.
>  	 *
>  	 * This callback is optional.
>  	 */