From: Boris Brezillon <boris.brezillon@collabora.com>
To: "Adrián Larumbe" <adrian.larumbe@collabora.com>
Cc: Qiang Yu <yuq825@gmail.com>,
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>,
Rob Herring <robh@kernel.org>,
Steven Price <steven.price@arm.com>,
Sumit Semwal <sumit.semwal@linaro.org>,
Christian Koenig= <christian.koenig@amd.com>,
Dmitry Osipenko <dmitry.osipenko@collabora.com>,
Zack Rusin <zack.rusin@broadcom.com>,
kernel@collabora.com, dri-devel@lists.freedesktop.org,
lima@lists.freedesktop.org, linux-kernel@vger.kernel.org,
linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org
Subject: Re: [PATCH v3 1/2] drm/panfrost: Fix dma_resv deadlock at drm object pin time
Date: Thu, 2 May 2024 09:09:36 +0200 [thread overview]
Message-ID: <20240502090936.2156c025@collabora.com> (raw)
In-Reply-To: <20240501065650.2809530-2-adrian.larumbe@collabora.com>
On Wed, 1 May 2024 07:55:59 +0100
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:
> When Panfrost must pin an object that is being prepared a dma-buf
> attachment for on behalf of another driver, the core drm gem object pinning
> code already takes a lock on the object's dma reservation.
>
> However, Panfrost GEM object's pinning callback would eventually try taking
> the lock on the same dma reservation when delegating pinning of the object
> onto the shmem subsystem, which led to a deadlock.
>
> This can be shown by enabling CONFIG_DEBUG_WW_MUTEX_SLOWPATH, which throws
> the following recursive locking situation:
>
> weston/3440 is trying to acquire lock:
> ffff000000e235a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: drm_gem_shmem_pin+0x34/0xb8 [drm_shmem_helper]
> but task is already holding lock:
> ffff000000e235a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: drm_gem_pin+0x2c/0x80 [drm]
>
> Fix it by assuming the object's reservation had already been locked by the
> time we reach panfrost_gem_pin.
You should probably mention that drm_gem_shmem_object_pin() assumes the
lock to be held, thus explaining the drm_gem_shmem_pin() ->
drm_gem_shmem_object_pin() transition.
Oh, and the commit message refers explicitly to Panfrost in a few places
even though you're fixing Lima as well.
>
> Do the same thing for the Lima driver, as it most likely suffers from the
> same issue.
>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> Cc: Boris Brezillon <boris.brezillon@collabora.com>
> Cc: Steven Price <steven.price@arm.com>
> Fixes: a78027847226 ("drm/gem: Acquire reservation lock in drm_gem_{pin/unpin}()")
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
With the commit message adjusted as suggested,
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> ---
> drivers/gpu/drm/lima/lima_gem.c | 2 +-
> drivers/gpu/drm/panfrost/panfrost_gem.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
> index 7ea244d876ca..c4e0f9faaa47 100644
> --- a/drivers/gpu/drm/lima/lima_gem.c
> +++ b/drivers/gpu/drm/lima/lima_gem.c
> @@ -185,7 +185,7 @@ static int lima_gem_pin(struct drm_gem_object *obj)
> if (bo->heap_size)
> return -EINVAL;
>
> - return drm_gem_shmem_pin(&bo->base);
> + return drm_gem_shmem_object_pin(obj);
> }
>
> static int lima_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index d47b40b82b0b..f268bd5c2884 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -192,7 +192,7 @@ static int panfrost_gem_pin(struct drm_gem_object *obj)
> if (bo->is_heap)
> return -EINVAL;
>
> - return drm_gem_shmem_pin(&bo->base);
> + return drm_gem_shmem_object_pin(obj);
> }
>
> static enum drm_gem_object_status panfrost_gem_status(struct drm_gem_object *obj)
next prev parent reply other threads:[~2024-05-02 7:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-01 6:55 [PATCH v3 0/2] drm: Fix dma_resv deadlock at drm object pin time Adrián Larumbe
2024-05-01 6:55 ` [PATCH v3 1/2] drm/panfrost: " Adrián Larumbe
2024-05-02 7:09 ` Boris Brezillon [this message]
2024-05-02 11:14 ` Thomas Zimmermann
2024-05-01 6:56 ` [PATCH v3 2/2] drm/gem-shmem: Add import attachment warning to locked pin function Adrián Larumbe
2024-05-02 7:01 ` Boris Brezillon
2024-05-02 11:51 ` [PATCH v3 0/2] drm: Fix dma_resv deadlock at drm object pin time Thomas Zimmermann
2024-05-02 11:59 ` Boris Brezillon
2024-05-02 12:00 ` Boris Brezillon
2024-05-02 12:18 ` Thomas Zimmermann
2024-05-17 18:16 ` Adrián Larumbe
2024-05-21 16:18 ` Boris Brezillon
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