linux-kernel - Re: [PATCH v4 2/3] drm/lima: Fix dma_resv deadlock at drm object pin time

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Message-ID: <20240523141321.52ea7224@collabora.com>
Date: Thu, 23 May 2024 14:13:21 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: Rob Herring <robh@...nel.org>, Steven Price <steven.price@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Sumit Semwal
 <sumit.semwal@...aro.org>, Christian König
 <christian.koenig@....com>, Dmitry Osipenko
 <dmitry.osipenko@...labora.com>, Zack Rusin <zack.rusin@...adcom.com>,
 kernel@...labora.com, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v4 2/3] drm/lima: Fix dma_resv deadlock at drm object
 pin time

On Thu, 23 May 2024 12:32:18 +0100
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> Commit a78027847226 ("drm/gem: Acquire reservation lock in
> drm_gem_{pin/unpin}()") moved locking the DRM object's dma reservation to
> drm_gem_pin(), but Lima's pin callback kept calling drm_gem_shmem_pin,
> which also tries to lock the same dma_resv, leading to a double lock
> situation.
> 
> As was already done for Panfrost in the previous commit, fix it by
> replacing drm_gem_shmem_pin() with its locked variant.
> 
> Cc: Thomas Zimmermann <tzimmermann@...e.de>
> Cc: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> Cc: Boris Brezillon <boris.brezillon@...labora.com>
> Cc: Steven Price <steven.price@....com>
> Fixes: a78027847226 ("drm/gem: Acquire reservation lock in drm_gem_{pin/unpin}()")
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>

> ---
>  drivers/gpu/drm/lima/lima_gem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
> index 7ea244d876ca..9bb997dbb4b9 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_pin_locked(&bo->base);
>  }
>  
>  static int lima_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)