[PATCH] drm: fix drm_mode_getconnector() locking imbalance regression

[PATCH] drm: fix drm_mode_getconnector() locking imbalance regression

[Tommi Rantala]

Regression in commit 2caa80e72b57c6216aec6f6a11fcfb4fec46daa0
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Sun Feb 22 11:38:36 2015 +0100

    drm: Fix deadlock due to getconnector locking changes

If the drm_connector_find() call returns NULL, we should no longer
call drm_modeset_unlock() to avoid locking imbalance.

Signed-off-by: Tommi Rantala <tt.rantala@gmail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/drm_crtc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 679b10e..b6f076b 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -2121,7 +2121,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
 	connector = drm_connector_find(dev, out_resp->connector_id);
 	if (!connector) {
 		ret = -ENOENT;
-		goto out;
+		goto out_unlock;
 	}
 
 	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++)
@@ -2201,6 +2201,8 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
 
 out:
 	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
+out_unlock:
 	mutex_unlock(&dev->mode_config.mutex);
 
 	return ret;
-- 
2.1.0

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Re: [PATCH] drm: fix drm_mode_getconnector() locking imbalance regression

[Daniel Vetter]

On Fri, Apr 03, 2015 at 10:45:29AM +0300, Tommi Rantala wrote:
> Regression in commit 2caa80e72b57c6216aec6f6a11fcfb4fec46daa0
> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> Date:   Sun Feb 22 11:38:36 2015 +0100
> 
>     drm: Fix deadlock due to getconnector locking changes
> 
> If the drm_connector_find() call returns NULL, we should no longer
> call drm_modeset_unlock() to avoid locking imbalance.
> 
> Signed-off-by: Tommi Rantala <tt.rantala@gmail.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>

Oops, thanks for catching this. If this missed 4.0 then we need to
backport it.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/drm_crtc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 679b10e..b6f076b 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -2121,7 +2121,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
>  	connector = drm_connector_find(dev, out_resp->connector_id);
>  	if (!connector) {
>  		ret = -ENOENT;
> -		goto out;
> +		goto out_unlock;
>  	}
>  
>  	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++)
> @@ -2201,6 +2201,8 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
>  
>  out:
>  	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +out_unlock:
>  	mutex_unlock(&dev->mode_config.mutex);
>  
>  	return ret;
> -- 
> 2.1.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH] drm: fix drm_mode_getconnector() locking imbalance regression

[Jani Nikula]

On Tue, 07 Apr 2015, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Fri, Apr 03, 2015 at 10:45:29AM +0300, Tommi Rantala wrote:
>> Regression in commit 2caa80e72b57c6216aec6f6a11fcfb4fec46daa0
>> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Date:   Sun Feb 22 11:38:36 2015 +0100
>> 
>>     drm: Fix deadlock due to getconnector locking changes
>> 
>> If the drm_connector_find() call returns NULL, we should no longer
>> call drm_modeset_unlock() to avoid locking imbalance.
>> 
>> Signed-off-by: Tommi Rantala <tt.rantala@gmail.com>
>> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> Oops, thanks for catching this. If this missed 4.0 then we need to
> backport it.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Pushed to topic/drm-fixes, should still make it to 4.0. Thanks for the
patch and review.

BR,
Jani.



>
>> ---
>>  drivers/gpu/drm/drm_crtc.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
>> index 679b10e..b6f076b 100644
>> --- a/drivers/gpu/drm/drm_crtc.c
>> +++ b/drivers/gpu/drm/drm_crtc.c
>> @@ -2121,7 +2121,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
>>  	connector = drm_connector_find(dev, out_resp->connector_id);
>>  	if (!connector) {
>>  		ret = -ENOENT;
>> -		goto out;
>> +		goto out_unlock;
>>  	}
>>  
>>  	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++)
>> @@ -2201,6 +2201,8 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
>>  
>>  out:
>>  	drm_modeset_unlock(&dev->mode_config.connection_mutex);
>> +
>> +out_unlock:
>>  	mutex_unlock(&dev->mode_config.mutex);
>>  
>>  	return ret;
>> -- 
>> 2.1.0
>> 
>
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Jani Nikula, Intel Open Source Technology Center
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