[PATCH] drm: Fixup locking WARNINGs in drm_mode_config_reset

[PATCH] drm: Fixup locking WARNINGs in drm_mode_config_reset

[Daniel Vetter]

With

commit 7a3f3d6667f5f9ffd1517f6b21d64bbf5312042c
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jul 9 23:44:28 2015 +0200

    drm: Check locking in drm_for_each_connector

we started checking the locking in drm_for_each_connector but somehow
I totally missed drm_mode_config_reset. There's no problem there since
this function should only be called in single-threaded contexts
(driver load or resume), so just wrap the loop with the right lock.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/drm_crtc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index c91c18b2b1d4..a8e5ca79aad1 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -5273,9 +5273,11 @@ void drm_mode_config_reset(struct drm_device *dev)
 		if (encoder->funcs->reset)
 			encoder->funcs->reset(encoder);
 
+	mutex_lock(dev->mode_config.mutex);
 	drm_for_each_connector(connector, dev)
 		if (connector->funcs->reset)
 			connector->funcs->reset(connector);
+	mutex_unlock(dev->mode_config.mutex);
 }
 EXPORT_SYMBOL(drm_mode_config_reset);
 
-- 
2.1.4

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[PATCH] drm: Fixup locking WARNINGs in drm_mode_config_reset

[Daniel Vetter]

With

commit 7a3f3d6667f5f9ffd1517f6b21d64bbf5312042c
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jul 9 23:44:28 2015 +0200

    drm: Check locking in drm_for_each_connector

we started checking the locking in drm_for_each_connector but somehow
I totally missed drm_mode_config_reset. There's no problem there since
this function should only be called in single-threaded contexts
(driver load or resume), so just wrap the loop with the right lock.

v2: Drink coffee and all that ...

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/drm_crtc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index c91c18b2b1d4..10c1a0f6680c 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -5273,9 +5273,11 @@ void drm_mode_config_reset(struct drm_device *dev)
 		if (encoder->funcs->reset)
 			encoder->funcs->reset(encoder);
 
+	mutex_lock(&dev->mode_config.mutex);
 	drm_for_each_connector(connector, dev)
 		if (connector->funcs->reset)
 			connector->funcs->reset(connector);
+	mutex_unlock(&dev->mode_config.mutex);
 }
 EXPORT_SYMBOL(drm_mode_config_reset);
 
-- 
2.1.4

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Re: [PATCH] drm: Fixup locking WARNINGs in drm_mode_config_reset

[Daniel Vetter]

On Wed, Jul 29, 2015 at 08:32:43AM +0200, Daniel Vetter wrote:
> With
> 
> commit 7a3f3d6667f5f9ffd1517f6b21d64bbf5312042c
> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> Date:   Thu Jul 9 23:44:28 2015 +0200
> 
>     drm: Check locking in drm_for_each_connector
> 
> we started checking the locking in drm_for_each_connector but somehow
> I totally missed drm_mode_config_reset. There's no problem there since
> this function should only be called in single-threaded contexts
> (driver load or resume), so just wrap the loop with the right lock.
> 
> v2: Drink coffee and all that ...
> 
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

Tested-by: Jianwei Wang <jianwei.wang.chn@gmail.com>

> ---
>  drivers/gpu/drm/drm_crtc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index c91c18b2b1d4..10c1a0f6680c 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -5273,9 +5273,11 @@ void drm_mode_config_reset(struct drm_device *dev)
>  		if (encoder->funcs->reset)
>  			encoder->funcs->reset(encoder);
>  
> +	mutex_lock(&dev->mode_config.mutex);
>  	drm_for_each_connector(connector, dev)
>  		if (connector->funcs->reset)
>  			connector->funcs->reset(connector);
> +	mutex_unlock(&dev->mode_config.mutex);
>  }
>  EXPORT_SYMBOL(drm_mode_config_reset);
>  
> -- 
> 2.1.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH] drm: Fixup locking WARNINGs in drm_mode_config_reset

[Laurent Pinchart]

Hi Daniel,

Thank you for the patch.

On Wednesday 29 July 2015 08:32:43 Daniel Vetter wrote:
> With
> 
> commit 7a3f3d6667f5f9ffd1517f6b21d64bbf5312042c
> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> Date:   Thu Jul 9 23:44:28 2015 +0200
> 
>     drm: Check locking in drm_for_each_connector
> 
> we started checking the locking in drm_for_each_connector but somehow
> I totally missed drm_mode_config_reset. There's no problem there since
> this function should only be called in single-threaded contexts
> (driver load or resume), so just wrap the loop with the right lock.
> 
> v2: Drink coffee and all that ...
> 
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

This gets rid of the warning at driver load time with the rcar-du-drm driver.

Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  drivers/gpu/drm/drm_crtc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index c91c18b2b1d4..10c1a0f6680c 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -5273,9 +5273,11 @@ void drm_mode_config_reset(struct drm_device *dev)
>  		if (encoder->funcs->reset)
>  			encoder->funcs->reset(encoder);
> 
> +	mutex_lock(&dev->mode_config.mutex);
>  	drm_for_each_connector(connector, dev)
>  		if (connector->funcs->reset)
>  			connector->funcs->reset(connector);
> +	mutex_unlock(&dev->mode_config.mutex);

Wouldn't it make sense to protect the whole function with the mode_config 
mutex, given that it's documented as "protecting the KMS related lists and 
structures" ?

>  }
>  EXPORT_SYMBOL(drm_mode_config_reset);

-- 
Regards,

Laurent Pinchart

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Re: [PATCH] drm: Fixup locking WARNINGs in drm_mode_config_reset

[Daniel Vetter]

On Wed, Jul 29, 2015 at 11:15:23PM +0300, Laurent Pinchart wrote:
> Hi Daniel,
> 
> Thank you for the patch.
> 
> On Wednesday 29 July 2015 08:32:43 Daniel Vetter wrote:
> > With
> > 
> > commit 7a3f3d6667f5f9ffd1517f6b21d64bbf5312042c
> > Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Date:   Thu Jul 9 23:44:28 2015 +0200
> > 
> >     drm: Check locking in drm_for_each_connector
> > 
> > we started checking the locking in drm_for_each_connector but somehow
> > I totally missed drm_mode_config_reset. There's no problem there since
> > this function should only be called in single-threaded contexts
> > (driver load or resume), so just wrap the loop with the right lock.
> > 
> > v2: Drink coffee and all that ...
> > 
> > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> 
> This gets rid of the warning at driver load time with the rcar-du-drm driver.
> 
> Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Thanks for testing, applied patch to drm-misc.
> 
> > ---
> >  drivers/gpu/drm/drm_crtc.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> > index c91c18b2b1d4..10c1a0f6680c 100644
> > --- a/drivers/gpu/drm/drm_crtc.c
> > +++ b/drivers/gpu/drm/drm_crtc.c
> > @@ -5273,9 +5273,11 @@ void drm_mode_config_reset(struct drm_device *dev)
> >  		if (encoder->funcs->reset)
> >  			encoder->funcs->reset(encoder);
> > 
> > +	mutex_lock(&dev->mode_config.mutex);
> >  	drm_for_each_connector(connector, dev)
> >  		if (connector->funcs->reset)
> >  			connector->funcs->reset(connector);
> > +	mutex_unlock(&dev->mode_config.mutex);
> 
> Wouldn't it make sense to protect the whole function with the mode_config 
> mutex, given that it's documented as "protecting the KMS related lists and 
> structures" ?

Well that was correct ages ago I guess but since then we've split out tons
of other locks. It doesn't protect anything else really since those lists
are all static after driver load, and even here it's just to shut up the
WARNING (which is right for runtime in general and not harmful to grab the
lock really either).

I do have a plan to fix up kerneldoc, but I want to get the various
improvements collabora is working on in first.
-Daniel

> 
> >  }
> >  EXPORT_SYMBOL(drm_mode_config_reset);
> 
> -- 
> Regards,
> 
> Laurent Pinchart
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH] drm: Fixup locking WARNINGs in drm_mode_config_reset

[shuang.he]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he@intel.com)
Task id: 6887
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
ILK                 -1              297/297              296/297
SNB                                  315/315              315/315
IVB                                  342/342              342/342
BYT                                  282/282              282/282
HSW                                  378/378              378/378
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*ILK  igt@kms_flip@flip-vs-dpms-interruptible      PASS(1)      DMESG_WARN(1)
Note: You need to pay more attention to line start with '*'
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