Re: [PATCH] drm/i915: Localise the fbdev console lock frobbing

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On Tue, Aug 12, 2014 at 03:15:17PM +0100, Chris Wilson wrote:
> Rather than take and release the console_lock() around a non-existent
> DRM_I915_FBDEV, move the lock acquisation into the callee where it will
> be compiled out by the config option entirely. This includes moving the
> deferred fb_set_suspend() dance and encapsulating it entirely within
> intel_fbdev.c.
> 
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
>  drivers/gpu/drm/i915/i915_dma.c    |  5 ++---
>  drivers/gpu/drm/i915/i915_drv.c    | 26 +-------------------------
>  drivers/gpu/drm/i915/i915_drv.h    |  8 --------
>  drivers/gpu/drm/i915/intel_fbdev.c | 33 +++++++++++++++++++++++++++++++++
>  4 files changed, 36 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 49149406fcd8..d0b3411fc13c 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -1339,8 +1339,6 @@ static int i915_load_modeset_init(struct drm_device *dev)
>  	if (ret)
>  		goto cleanup_irq;
>  
> -	INIT_WORK(&dev_priv->console_resume_work, intel_console_resume);
> -
>  	intel_modeset_gem_init(dev);
>  
>  	/* Always safe in the mode setting case. */
> @@ -1835,6 +1833,8 @@ int i915_driver_unload(struct drm_device *dev)
>  		return ret;
>  	}
>  
> +	flush_scheduled_work();

Tbh I prefer the explicit work flushing and keeping it in dev_priv. We can
shovel it into the I915_FBDEV #ifdef that's already there though.

> +
>  	i915_perf_unregister(dev);
>  	intel_fini_runtime_pm(dev_priv);
>  
> @@ -1859,7 +1859,6 @@ int i915_driver_unload(struct drm_device *dev)
>  	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
>  		intel_fbdev_fini(dev);
>  		intel_modeset_cleanup(dev);
> -		cancel_work_sync(&dev_priv->console_resume_work);
>  
>  		/*
>  		 * free the memory space allocated for the child device
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 35b119072c11..9adafc7c5819 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -558,9 +558,7 @@ static int i915_drm_freeze(struct drm_device *dev)
>  	intel_uncore_forcewake_reset(dev, false);
>  	intel_opregion_fini(dev);
>  
> -	console_lock();
>  	intel_fbdev_set_suspend(dev, FBINFO_STATE_SUSPENDED);

This one here must be synchronous.

> -	console_unlock();
>  
>  	dev_priv->suspend_count++;
>  
> @@ -599,18 +597,6 @@ int i915_suspend(struct drm_device *dev, pm_message_t state)
>  	return 0;
>  }
>  
> -void intel_console_resume(struct work_struct *work)
> -{
> -	struct drm_i915_private *dev_priv =
> -		container_of(work, struct drm_i915_private,
> -			     console_resume_work);
> -	struct drm_device *dev = dev_priv->dev;
> -
> -	console_lock();
> -	intel_fbdev_set_suspend(dev, FBINFO_STATE_RUNNING);
> -	console_unlock();
> -}
> -
>  static int i915_drm_thaw_early(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> @@ -683,17 +669,7 @@ static int __i915_drm_thaw(struct drm_device *dev, bool restore_gtt_mappings)
>  
>  	intel_opregion_init(dev);
>  
> -	/*
> -	 * The console lock can be pretty contented on resume due
> -	 * to all the printk activity.  Try to keep it out of the hot
> -	 * path of resume if possible.
> -	 */
> -	if (console_trylock()) {
> -		intel_fbdev_set_suspend(dev, FBINFO_STATE_RUNNING);
> -		console_unlock();
> -	} else {
> -		schedule_work(&dev_priv->console_resume_work);
> -	}
> +	intel_fbdev_set_suspend(dev, FBINFO_STATE_RUNNING);
>  
>  	mutex_lock(&dev_priv->modeset_restore_lock);
>  	dev_priv->modeset_restore = MODESET_DONE;
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 517a78e27bbb..e38dd39d84ad 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1603,12 +1603,6 @@ struct drm_i915_private {
>  	struct intel_fbdev *fbdev;
>  #endif
>  
> -	/*
> -	 * The console may be contended at resume, but we don't
> -	 * want it to block on it.
> -	 */
> -	struct work_struct console_resume_work;
> -
>  	struct drm_property *broadcast_rgb_property;
>  	struct drm_property *force_audio_property;
>  
> @@ -2310,8 +2304,6 @@ extern unsigned long i915_gfx_val(struct drm_i915_private *dev_priv);
>  extern void i915_update_gfx_val(struct drm_i915_private *dev_priv);
>  int vlv_force_gfx_clock(struct drm_i915_private *dev_priv, bool on);
>  
> -extern void intel_console_resume(struct work_struct *work);
> -
>  /* i915_irq.c */
>  void i915_queue_hangcheck(struct drm_device *dev);
>  __printf(3, 4)
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> index 5d879d185fe1..4eecb34a0e32 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -26,6 +26,7 @@
>  
>  #include <linux/module.h>
>  #include <linux/kernel.h>
> +#include <linux/console.h>
>  #include <linux/errno.h>
>  #include <linux/string.h>
>  #include <linux/mm.h>
> @@ -678,6 +679,19 @@ void intel_fbdev_fini(struct drm_device *dev)
>  	dev_priv->fbdev = NULL;
>  }
>  
> +struct set_suspend_work {
> +	struct work_struct work;
> +	struct drm_device *dev;
> +	int state;
> +};
> +
> +static void intel_fbdev_set_suspend_worker(struct work_struct *work)
> +{
> +	struct set_suspend_work *ss = container_of(work, typeof(*ss), work);
> +	intel_fbdev_set_suspend(ss->dev, ss->state);

This still trylocks so ends up busy-looping through launching more work
items. Probably better also do this synchronously.
-Daniel

> +	kfree(ss);
> +}
> +
>  void intel_fbdev_set_suspend(struct drm_device *dev, int state)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> @@ -689,6 +703,24 @@ void intel_fbdev_set_suspend(struct drm_device *dev, int state)
>  
>  	info = ifbdev->helper.fbdev;
>  
> +	/*
> +	 * The console lock can be pretty contented on resume due
> +	 * to all the printk activity.  Try to keep it out of the hot
> +	 * path of resume if possible.
> +	 */
> +	if (!console_trylock()) {
> +		struct set_suspend_work *ss;
> +
> +		ss = kmalloc(sizeof(*ss), GFP_KERNEL);
> +		if (ss) {
> +			ss->dev = dev;
> +			ss->state = state;
> +			INIT_WORK(&ss->work, intel_fbdev_set_suspend_worker);
> +			schedule_work(&ss->work);
> +		}
> +		return;
> +	}
> +
>  	/* On resume from hibernation: If the object is shmemfs backed, it has
>  	 * been restored from swap. If the object is stolen however, it will be
>  	 * full of whatever garbage was left in there.
> @@ -697,6 +729,7 @@ void intel_fbdev_set_suspend(struct drm_device *dev, int state)
>  		memset_io(info->screen_base, 0, info->screen_size);
>  
>  	fb_set_suspend(info, state);
> +	console_unlock();
>  }
>  
>  void intel_fbdev_output_poll_changed(struct drm_device *dev)
> -- 
> 2.1.0.rc1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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