[PATCH 1/2] media: exynos4-is: fix deadlock on driver probe

[PATCH 1/2] media: exynos4-is: fix deadlock on driver probe

[Marek Szyprowski]

Commit 0c426c472b5585ed6e59160359c979506d45ae49 ("[media] media: Always
keep a graph walk large enough around") changed
media_device_register_entity() function to take mdev->graph_mutex. This
causes deadlock in driver probe, which calls (indirectly) this function
with ->graph_mutex taken. This patch removes taking ->graph_mutex in
driver probe to avoid deadlock. Other drivers don't take ->graph_mutex
for entity registration, so this change should be safe.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/media/platform/exynos4-is/media-dev.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/drivers/media/platform/exynos4-is/media-dev.c b/drivers/media/platform/exynos4-is/media-dev.c
index 04348b502232..891625e77ef5 100644
--- a/drivers/media/platform/exynos4-is/media-dev.c
+++ b/drivers/media/platform/exynos4-is/media-dev.c
@@ -1448,22 +1448,13 @@ static int fimc_md_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, fmd);
 
-	/* Protect the media graph while we're registering entities */
-	mutex_lock(&fmd->media_dev.graph_mutex);
-
 	ret = fimc_md_register_platform_entities(fmd, dev->of_node);
-	if (ret) {
-		mutex_unlock(&fmd->media_dev.graph_mutex);
+	if (ret)
 		goto err_clk;
-	}
 
 	ret = fimc_md_register_sensor_entities(fmd);
-	if (ret) {
-		mutex_unlock(&fmd->media_dev.graph_mutex);
+	if (ret)
 		goto err_m_ent;
-	}
-
-	mutex_unlock(&fmd->media_dev.graph_mutex);
 
 	ret = device_create_file(&pdev->dev, &dev_attr_subdev_conf_mode);
 	if (ret)
-- 
1.9.2

[PATCH 2/2] media: s3c-camif: fix deadlock on driver probe()

[Marek Szyprowski]

Commit 0c426c472b5585ed6e59160359c979506d45ae49 ("[media] media: Always
keep a graph walk large enough around") changed
media_device_register_entity() function to take mdev->graph_mutex. This
causes deadlock in driver probe, which calls (indirectly) this function
with ->graph_mutex taken. This patch removes taking ->graph_mutex in
driver probe to avoid deadlock. Other drivers don't take ->graph_mutex
for entity registration, so this change should be safe.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 drivers/media/platform/s3c-camif/camif-core.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/media/platform/s3c-camif/camif-core.c b/drivers/media/platform/s3c-camif/camif-core.c
index 0b44b9accf50..af237af204e2 100644
--- a/drivers/media/platform/s3c-camif/camif-core.c
+++ b/drivers/media/platform/s3c-camif/camif-core.c
@@ -493,21 +493,17 @@ static int s3c_camif_probe(struct platform_device *pdev)
 	if (ret < 0)
 		goto err_sens;
 
-	mutex_lock(&camif->media_dev.graph_mutex);
-
 	ret = v4l2_device_register_subdev_nodes(&camif->v4l2_dev);
 	if (ret < 0)
-		goto err_unlock;
+		goto err_sens;
 
 	ret = camif_register_video_nodes(camif);
 	if (ret < 0)
-		goto err_unlock;
+		goto err_sens;
 
 	ret = camif_create_media_links(camif);
 	if (ret < 0)
-		goto err_unlock;
-
-	mutex_unlock(&camif->media_dev.graph_mutex);
+		goto err_sens;
 
 	ret = media_device_register(&camif->media_dev);
 	if (ret < 0)
@@ -516,8 +512,6 @@ static int s3c_camif_probe(struct platform_device *pdev)
 	pm_runtime_put(dev);
 	return 0;
 
-err_unlock:
-	mutex_unlock(&camif->media_dev.graph_mutex);
 err_sens:
 	v4l2_device_unregister(&camif->v4l2_dev);
 	media_device_unregister(&camif->media_dev);
-- 
1.9.2

Re: [PATCH 2/2] media: s3c-camif: fix deadlock on driver probe()

[Hans Verkuil]

On 04/28/16 12:25, Marek Szyprowski wrote:
> Commit 0c426c472b5585ed6e59160359c979506d45ae49 ("[media] media: Always
> keep a graph walk large enough around") changed
> media_device_register_entity() function to take mdev->graph_mutex. This
> causes deadlock in driver probe, which calls (indirectly) this function
> with ->graph_mutex taken. This patch removes taking ->graph_mutex in
> driver probe to avoid deadlock. Other drivers don't take ->graph_mutex
> for entity registration, so this change should be safe.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>

Thanks!

	Hans

> ---
>  drivers/media/platform/s3c-camif/camif-core.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/media/platform/s3c-camif/camif-core.c b/drivers/media/platform/s3c-camif/camif-core.c
> index 0b44b9accf50..af237af204e2 100644
> --- a/drivers/media/platform/s3c-camif/camif-core.c
> +++ b/drivers/media/platform/s3c-camif/camif-core.c
> @@ -493,21 +493,17 @@ static int s3c_camif_probe(struct platform_device *pdev)
>  	if (ret < 0)
>  		goto err_sens;
>  
> -	mutex_lock(&camif->media_dev.graph_mutex);
> -
>  	ret = v4l2_device_register_subdev_nodes(&camif->v4l2_dev);
>  	if (ret < 0)
> -		goto err_unlock;
> +		goto err_sens;
>  
>  	ret = camif_register_video_nodes(camif);
>  	if (ret < 0)
> -		goto err_unlock;
> +		goto err_sens;
>  
>  	ret = camif_create_media_links(camif);
>  	if (ret < 0)
> -		goto err_unlock;
> -
> -	mutex_unlock(&camif->media_dev.graph_mutex);
> +		goto err_sens;
>  
>  	ret = media_device_register(&camif->media_dev);
>  	if (ret < 0)
> @@ -516,8 +512,6 @@ static int s3c_camif_probe(struct platform_device *pdev)
>  	pm_runtime_put(dev);
>  	return 0;
>  
> -err_unlock:
> -	mutex_unlock(&camif->media_dev.graph_mutex);
>  err_sens:
>  	v4l2_device_unregister(&camif->v4l2_dev);
>  	media_device_unregister(&camif->media_dev);
> 

Re: [PATCH 1/2] media: exynos4-is: fix deadlock on driver probe

[Sakari Ailus]

Hi Marek,

Marek Szyprowski wrote:
> Commit 0c426c472b5585ed6e59160359c979506d45ae49 ("[media] media: Always
> keep a graph walk large enough around") changed
> media_device_register_entity() function to take mdev->graph_mutex. This
> causes deadlock in driver probe, which calls (indirectly) this function
> with ->graph_mutex taken. This patch removes taking ->graph_mutex in
> driver probe to avoid deadlock. Other drivers don't take ->graph_mutex
> for entity registration, so this change should be safe.
>
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>

You could also add:

Fixes: 0c426c472b55 ("[media] media: Always keep a graph walk large 
enough around")

I guess these should go to fixes, the patches in question are already 
heading for v4.6. Cc Mauro.

-- 
Kind regards,

Sakari Ailus
sakari.ailus@linux.intel.com

Re: [PATCH 1/2] media: exynos4-is: fix deadlock on driver probe

[Mauro Carvalho Chehab]

Em Mon, 2 May 2016 00:59:56 +0300
Sakari Ailus <sakari.ailus@linux.intel.com> escreveu:

> Hi Marek,
> 
> Marek Szyprowski wrote:
> > Commit 0c426c472b5585ed6e59160359c979506d45ae49 ("[media] media: Always
> > keep a graph walk large enough around") changed
> > media_device_register_entity() function to take mdev->graph_mutex. This
> > causes deadlock in driver probe, which calls (indirectly) this function
> > with ->graph_mutex taken. This patch removes taking ->graph_mutex in
> > driver probe to avoid deadlock. Other drivers don't take ->graph_mutex
> > for entity registration, so this change should be safe.
> >
> > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>  
> 
> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> 
> You could also add:
> 
> Fixes: 0c426c472b55 ("[media] media: Always keep a graph walk large 
> enough around")
> 
> I guess these should go to fixes, the patches in question are already 
> heading for v4.6. Cc Mauro.

The patches from Sakari for v4.6 were merged already at -rc6. Just merged
them back at the master branch.

Regards,
Mauro

Re: [PATCH 1/2] media: exynos4-is: fix deadlock on driver probe

[Hans Verkuil]

On 05/02/16 12:52, Mauro Carvalho Chehab wrote:
> Em Mon, 2 May 2016 00:59:56 +0300
> Sakari Ailus <sakari.ailus@linux.intel.com> escreveu:
> 
>> Hi Marek,
>>
>> Marek Szyprowski wrote:
>>> Commit 0c426c472b5585ed6e59160359c979506d45ae49 ("[media] media: Always
>>> keep a graph walk large enough around") changed
>>> media_device_register_entity() function to take mdev->graph_mutex. This
>>> causes deadlock in driver probe, which calls (indirectly) this function
>>> with ->graph_mutex taken. This patch removes taking ->graph_mutex in
>>> driver probe to avoid deadlock. Other drivers don't take ->graph_mutex
>>> for entity registration, so this change should be safe.
>>>
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>  
>>
>> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>>
>> You could also add:
>>
>> Fixes: 0c426c472b55 ("[media] media: Always keep a graph walk large 
>> enough around")
>>
>> I guess these should go to fixes, the patches in question are already 
>> heading for v4.6. Cc Mauro.
> 
> The patches from Sakari for v4.6 were merged already at -rc6. Just merged
> them back at the master branch.

I'm confused. The two patches from Marek fixing driver probe deadlock are not
in the master tree (just pulled from it, it's now rc6), so the deadlock still
happens in kernel 4.6.

Regards,

	Hans

Re: [PATCH 1/2] media: exynos4-is: fix deadlock on driver probe

[Hans Verkuil]

On 04/28/2016 12:25 PM, Marek Szyprowski wrote:
> Commit 0c426c472b5585ed6e59160359c979506d45ae49 ("[media] media: Always
> keep a graph walk large enough around") changed
> media_device_register_entity() function to take mdev->graph_mutex. This
> causes deadlock in driver probe, which calls (indirectly) this function
> with ->graph_mutex taken. This patch removes taking ->graph_mutex in
> driver probe to avoid deadlock. Other drivers don't take ->graph_mutex
> for entity registration, so this change should be safe.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Hans Verkuil <hans.verkuil@cisco.com>

Thanks!

	Hans

> ---
>  drivers/media/platform/exynos4-is/media-dev.c | 13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/media/platform/exynos4-is/media-dev.c b/drivers/media/platform/exynos4-is/media-dev.c
> index 04348b502232..891625e77ef5 100644
> --- a/drivers/media/platform/exynos4-is/media-dev.c
> +++ b/drivers/media/platform/exynos4-is/media-dev.c
> @@ -1448,22 +1448,13 @@ static int fimc_md_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, fmd);
>  
> -	/* Protect the media graph while we're registering entities */
> -	mutex_lock(&fmd->media_dev.graph_mutex);
> -
>  	ret = fimc_md_register_platform_entities(fmd, dev->of_node);
> -	if (ret) {
> -		mutex_unlock(&fmd->media_dev.graph_mutex);
> +	if (ret)
>  		goto err_clk;
> -	}
>  
>  	ret = fimc_md_register_sensor_entities(fmd);
> -	if (ret) {
> -		mutex_unlock(&fmd->media_dev.graph_mutex);
> +	if (ret)
>  		goto err_m_ent;
> -	}
> -
> -	mutex_unlock(&fmd->media_dev.graph_mutex);
>  
>  	ret = device_create_file(&pdev->dev, &dev_attr_subdev_conf_mode);
>  	if (ret)
>