linux-kernel - Re: [PATCH] drm: Fixup hang when unregistering drm dev with open

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Date:   Tue, 11 Apr 2017 17:05:03 -0400
From:   Sean Paul <seanpaul@...omium.org>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     linux-kernel@...r.kernel.org, briannorris@...omium.org,
        dianders@...omium.org, tfiga@...omium.org, seanpaul@...omium.org,
        zyw@...k-chips.com, marcheu@...omium.org, mark.yao@...k-chips.com,
        hshi@...omium.org, Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH] drm: Fixup hang when unregistering drm dev with
 open_count 0

On Wed, Apr 12, 2017 at 04:57:54AM +0800, Jeffy Chen wrote:
> My previous patch (c5d8fac2bf  drm: Unplug drm device when unregistering
> it) calls drm_unplug_dev when unregistering drm dev. But if open_count
> is 0, the unplug will try to unregister the drm dev again and cause
> deadlock.
> 
> Fix it by dropping drm_unplug_dev and use drm_device_set_plug_state
> directly.

Hi Jeffy,
That patch was not applied anywhere, the test robot just picked it up from the
mailing list.

Please squash this into the original patch and re-send.

Thanks,

Sean

> 
> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
> 
> ---
> 
>  drivers/gpu/drm/drm_drv.c | 15 +--------------
>  include/drm/drm_drv.h     |  1 -
>  2 files changed, 1 insertion(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index ad13e20..cc2d018 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -355,19 +355,6 @@ void drm_put_dev(struct drm_device *dev)
>  }
>  EXPORT_SYMBOL(drm_put_dev);
>  
> -void drm_unplug_dev(struct drm_device *dev)
> -{
> -	mutex_lock(&drm_global_mutex);
> -
> -	drm_device_set_plug_state(dev, false);
> -
> -	if (dev->open_count == 0) {
> -		drm_put_dev(dev);
> -	}
> -	mutex_unlock(&drm_global_mutex);
> -}
> -EXPORT_SYMBOL(drm_unplug_dev);
> -
>  /*
>   * DRM internal mount
>   * We want to be able to allocate our own "struct address_space" to control
> @@ -825,7 +812,7 @@ void drm_dev_unregister(struct drm_device *dev)
>  	drm_lastclose(dev);
>  
>  	dev->registered = false;
> -	drm_unplug_dev(dev);
> +	drm_device_set_plug_state(dev, false);
>  
>  	if (drm_core_check_feature(dev, DRIVER_MODESET))
>  		drm_modeset_unregister_all(dev);
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index 0fefc3f..eb63078 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev);
>  void drm_dev_ref(struct drm_device *dev);
>  void drm_dev_unref(struct drm_device *dev);
>  void drm_put_dev(struct drm_device *dev);
> -void drm_unplug_dev(struct drm_device *dev);
>  
>  int drm_dev_set_unique(struct drm_device *dev, const char *name);
>  
> -- 
> 2.1.4
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS