Message-ID: <a1cd8c74-98f4-bff0-0344-cbece787c6e8@redhat.com>
Date:   Mon, 6 Feb 2023 19:47:13 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.6.0
Subject: Re: [PATCH] drm/shmem-helper: Fix locking for
 drm_gem_shmem_get_pages_sgt()
Content-Language: en-US
To:     Asahi Lina <lina@asahilina.net>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>
Cc:     linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= <noralf@tronnes.org>,
        asahi@lists.linux.dev, Alyssa Rosenzweig <alyssa@rosenzweig.io>
References: <20230205125124.2260-1-lina@asahilina.net>
From:   Javier Martinez Canillas <javierm@redhat.com>
In-Reply-To: <20230205125124.2260-1-lina@asahilina.net>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hello Lina,

On 2/5/23 13:51, Asahi Lina wrote:
> Other functions touching shmem->sgt take the pages lock, so do that here
> too. drm_gem_shmem_get_pages() & co take the same lock, so move to the
> _locked() variants to avoid recursive locking.
> 
> Discovered while auditing locking to write the Rust abstractions.
> 
> Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects")
> Fixes: 4fa3d66f132b ("drm/shmem: Do dma_unmap_sg before purging pages")
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> ---

Good catch. The patch looks good to me.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>

What about drm_gem_shmem_free() BTW, I believe that the helper should also
grab the lock before unmap / free the sgtable?

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat