linux-kernel - Re: [PATCH v2 1/7] media: videobuf2: Don't assert held reservation lock for dma-buf mmapping

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Date:   Wed, 12 Apr 2023 16:39:44 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        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>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Amol Maheshwari <amahesh@....qualcomm.com>,
        Emil Velikov <emil.l.velikov@...il.com>
Cc:     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, linux-arm-msm@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH v2 1/7] media: videobuf2: Don't assert held reservation
 lock for dma-buf mmapping

On 06/04/2023 18:06, Dmitry Osipenko wrote:
> Don't assert held dma-buf reservation lock on memory mapping of exported
> buffer.
> 
> We're going to change dma-buf mmap() locking policy such that exporters
> will have to handle the lock. The previous locking policy caused deadlock
> problem for DRM drivers in a case of self-imported dma-bufs once these
> drivers are moved to use reservation lock universally. The problem is
> solved by moving the lock down to exporters. This patch prepares videobuf2
> for the locking policy update.
> 
> Reviewed-by: Emil Velikov <emil.l.velikov@...il.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>

Reviewed-by: Hans Verkuil <hverkuil-cisco@...all.nl>

Regards,

	Hans

> ---
>  drivers/media/common/videobuf2/videobuf2-dma-contig.c | 3 ---
>  drivers/media/common/videobuf2/videobuf2-dma-sg.c     | 3 ---
>  drivers/media/common/videobuf2/videobuf2-vmalloc.c    | 3 ---
>  3 files changed, 9 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> index 205d3cac425c..2fa455d4a048 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> @@ -11,7 +11,6 @@
>   */
>  
>  #include <linux/dma-buf.h>
> -#include <linux/dma-resv.h>
>  #include <linux/module.h>
>  #include <linux/refcount.h>
>  #include <linux/scatterlist.h>
> @@ -456,8 +455,6 @@ static int vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf, struct iosys_map *map)
>  static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
>  	struct vm_area_struct *vma)
>  {
> -	dma_resv_assert_held(dbuf->resv);
> -
>  	return vb2_dc_mmap(dbuf->priv, vma);
>  }
>  
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> index 183037fb1273..28f3fdfe23a2 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> @@ -10,7 +10,6 @@
>   * the Free Software Foundation.
>   */
>  
> -#include <linux/dma-resv.h>
>  #include <linux/module.h>
>  #include <linux/mm.h>
>  #include <linux/refcount.h>
> @@ -498,8 +497,6 @@ static int vb2_dma_sg_dmabuf_ops_vmap(struct dma_buf *dbuf,
>  static int vb2_dma_sg_dmabuf_ops_mmap(struct dma_buf *dbuf,
>  	struct vm_area_struct *vma)
>  {
> -	dma_resv_assert_held(dbuf->resv);
> -
>  	return vb2_dma_sg_mmap(dbuf->priv, vma);
>  }
>  
> diff --git a/drivers/media/common/videobuf2/videobuf2-vmalloc.c b/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> index a6c6d2fcaaa4..7c635e292106 100644
> --- a/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> +++ b/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> @@ -10,7 +10,6 @@
>   * the Free Software Foundation.
>   */
>  
> -#include <linux/dma-resv.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
>  #include <linux/mm.h>
> @@ -319,8 +318,6 @@ static int vb2_vmalloc_dmabuf_ops_vmap(struct dma_buf *dbuf,
>  static int vb2_vmalloc_dmabuf_ops_mmap(struct dma_buf *dbuf,
>  	struct vm_area_struct *vma)
>  {
> -	dma_resv_assert_held(dbuf->resv);
> -
>  	return vb2_vmalloc_mmap(dbuf->priv, vma);
>  }
>