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Date:   Thu, 17 Mar 2022 20:45:33 +0300
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Subject: Re: [PATCH v2 6/8] drm/shmem-helper: Add generic memory shrinker
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To:     David Airlie <airlied@linux.ie>, Gerd Hoffmann <kraxel@redhat.com>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Chia-I Wu <olvaffe@gmail.com>,
        Daniel Almeida <daniel.almeida@collabora.com>,
        Gert Wollny <gert.wollny@collabora.com>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Rob Herring <robh@kernel.org>,
        Steven Price <steven.price@arm.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Gustavo Padovan <gustavo.padovan@collabora.com>,
        Daniel Stone <daniel@fooishbar.org>,
        virtualization@lists.linux-foundation.org,
        Dmitry Osipenko <digetx@gmail.com>
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From:   Dmitry Osipenko <dmitry.osipenko@collabora.com>
In-Reply-To: <YjNwnOMvboOkGm4w@phenom.ffwll.local>
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On 3/17/22 20:32, Daniel Vetter wrote:
>> +static void drm_gem_shmem_update_purgeable_status(struct drm_gem_shmem_object *shmem)
>> +{
>> +	struct drm_gem_object *obj = &shmem->base;
>> +	struct drm_gem_shmem_shrinker *gem_shrinker = obj->dev->shmem_shrinker;
>> +	size_t page_count = obj->size >> PAGE_SHIFT;
>> +
>> +	if (!gem_shrinker || obj->import_attach || !obj->funcs->purge)
>> +		return;
>> +
>> +	mutex_lock(&shmem->vmap_lock);
>> +	mutex_lock(&shmem->pages_lock);
>> +	mutex_lock(&gem_shrinker->lock);
> Uh this is just terrible I think.
> 
> Can't we move shmem helpers over to reasonable locking, i.e. per-object
> dma_resv_lock for everything? I know it's a pile of work, but I think
> we're way past the point with things like this popping up where we should
> just bite that bullet.
> 
> I discussed the full thing with Daniel Stone, but maybe a joint refresher
> on irc would be a good thing.

Aha! Perhaps I saw bits of that discussion, but it wasn't entirely clear
to me what was discussed in fact. Sounds like a good idea to try to use
the reservation lock everywhere, thank you for the suggestion.