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Date:   Wed, 10 Aug 2022 20:49:52 +0300
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Subject: Re: [Linaro-mm-sig] [PATCH v2 3/5] dma-buf: Move all dma-bufs to
 dynamic locking specification
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To:     =?UTF-8?Q?Christian_K=c3=b6nig?= <ckoenig.leichtzumerken@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Gerd Hoffmann <kraxel@redhat.com>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        Daniel Almeida <daniel.almeida@collabora.com>,
        Gert Wollny <gert.wollny@collabora.com>,
        Gustavo Padovan <gustavo.padovan@collabora.com>,
        Daniel Stone <daniel@fooishbar.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Rob Clark <robdclark@gmail.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Tomasz Figa <tfiga@chromium.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= <thomas_os@shipmail.org>
Cc:     dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Dmitry Osipenko <digetx@gmail.com>,
        linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org,
        amd-gfx@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
        kernel@collabora.com, virtualization@lists.linux-foundation.org,
        spice-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org,
        linux-arm-msm@vger.kernel.org
References: <20220725151839.31622-1-dmitry.osipenko@collabora.com>
 <20220725151839.31622-4-dmitry.osipenko@collabora.com>
 <6c8bded9-1809-608f-749a-5ee28b852d32@gmail.com>
From:   Dmitry Osipenko <dmitry.osipenko@collabora.com>
In-Reply-To: <6c8bded9-1809-608f-749a-5ee28b852d32@gmail.com>
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On 8/10/22 14:30, Christian König wrote:
> Am 25.07.22 um 17:18 schrieb Dmitry Osipenko:
>> This patch moves the non-dynamic dma-buf users over to the dynamic
>> locking specification. The strict locking convention prevents deadlock
>> situation for dma-buf importers and exporters.
>>
>> Previously the "unlocked" versions of the dma-buf API functions weren't
>> taking the reservation lock and this patch makes them to take the lock.
>>
>> Intel and AMD GPU drivers already were mapping imported dma-bufs under
>> the held lock, hence the "locked" variant of the functions are added
>> for them and the drivers are updated to use the "locked" versions.
> 
> In general "Yes, please", but that won't be that easy.
> 
> You not only need to change amdgpu and i915, but all drivers
> implementing the map_dma_buf(), unmap_dma_buf() callbacks.
> 
> Auditing all that code is a huge bunch of work.
Hm, neither of drivers take the resv lock in map_dma_buf/unmap_dma_buf.
It's easy to audit them all and I did it. So either I'm missing
something or it doesn't take much time to check them all. Am I really
missing something?

https://elixir.bootlin.com/linux/latest/A/ident/map_dma_buf

-- 
Best regards,
Dmitry