linux-kernel - Re: [PATCH v3 6/6] drm/shmem-helper: Switch to reservation lock

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Message-ID: <CACvgo52QvmZw5k_9dmBHPB25rTdLZJzVG_vNFr8or+3f5sVO=Q@mail.gmail.com>
Date:   Mon, 22 May 2023 14:02:19 +0100
From:   Emil Velikov <emil.l.velikov@...il.com>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc:     Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Liam Mark <lmark@...eaurora.org>,
        Brian Starkey <Brian.Starkey@....com>,
        John Stultz <jstultz@...gle.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Tomi Valkeinen <tomba@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        linux-tegra@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH v3 6/6] drm/shmem-helper: Switch to reservation lock

Hi Dmitry,

Saw v3 fly by, so I had a quick look. Original RB still stands,
although I noticed a couple of non-blocking nitpicks.

On Sun, 21 May 2023 at 22:00, Dmitry Osipenko
<dmitry.osipenko@...labora.com> wrote:

> -static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
> +static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
>  {

Should this getter have a dma_resv_assert_held(shmem->base.resv); like
it's put brethren?


> -void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
> +static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
> +{
> +       int ret;
> +
> +       dma_resv_assert_held(shmem->base.resv);
> +
> +       ret = drm_gem_shmem_get_pages(shmem);
> +
> +       return ret;

With the assert_held in the getter, it would be less confusing to
inline this and the unpin_locked functions.

> +}
> +
> +static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
>  {
> -       mutex_lock(&shmem->pages_lock);
> -       drm_gem_shmem_put_pages_locked(shmem);
> -       mutex_unlock(&shmem->pages_lock);
> +       dma_resv_assert_held(shmem->base.resv);
> +
> +       drm_gem_shmem_put_pages(shmem);

Side note: the putter has an assert_held so the extra one here seems quite odd.

As said at the top - with or w/o these nitpicks, the original RB still stands.

HTH o/
-Emil