[Intel-gfx] [PATCH RESEND FOR CI] drm/i915: Fix races on fbdev

Lukas Wunner lukas at wunner.de
Thu Mar 3 18:30:33 UTC 2016


Hi Damien, Hi Daniel,

I've submitted the patch below for the third time now in an attempt
to get CI to test it, again to no avail. This time I didn't set the
In-Reply-To header and only submitted it as a single patch instead
of as a series because I expected this might confuse CI.

Nevertheless CI misclassified it under "Series" instead of "Patches",
reports that the series consists of 0 patches and doesn't test it:
https://patchwork.freedesktop.org/series/4068/

Earlier attempts:
https://patchwork.freedesktop.org/series/3453/
https://patchwork.freedesktop.org/series/3126/

Sorry, I give up.

Best regards,

Lukas

On Thu, Mar 03, 2016 at 06:02:53PM +0100, Lukas Wunner wrote:
> The ->lastclose callback invokes intel_fbdev_restore_mode() and has
> been witnessed to run before intel_fbdev_initial_config_async()
> has finished.
> 
> We might likewise receive hotplug events or be suspended before
> we've had a chance to fully set up the fbdev.
> 
> Fix by waiting for the asynchronous thread to finish.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93580
> Reported-by: Gustav F├Ągerlind <gustav.fagerlind at gmail.com>
> Reported-by: "Li, Weinan Z" <weinan.z.li at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: stable at vger.kernel.org
> Signed-off-by: Lukas Wunner <lukas at wunner.de>
> ---
>  drivers/gpu/drm/i915/i915_dma.c    | 8 +++-----
>  drivers/gpu/drm/i915/intel_fbdev.c | 4 ++++
>  2 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 4aa3db6..9d76dfb 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -430,11 +430,9 @@ static int i915_load_modeset_init(struct drm_device *dev)
>  	 * Some ports require correctly set-up hpd registers for detection to
>  	 * work properly (leading to ghost connected connector status), e.g. VGA
>  	 * on gm45.  Hence we can only set up the initial fbdev config after hpd
> -	 * irqs are fully enabled. Now we should scan for the initial config
> -	 * only once hotplug handling is enabled, but due to screwed-up locking
> -	 * around kms/fbdev init we can't protect the fdbev initial config
> -	 * scanning against hotplug events. Hence do this first and ignore the
> -	 * tiny window where we will loose hotplug notifactions.
> +	 * irqs are fully enabled. We protect the fbdev initial config scanning
> +	 * against hotplug events by waiting in intel_fbdev_output_poll_changed
> +	 * until the asynchronous thread has finished.
>  	 */
>  	intel_fbdev_initial_config_async(dev);
>  
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> index ae9cf6f..936c3d7 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -754,6 +754,7 @@ void intel_fbdev_set_suspend(struct drm_device *dev, int state, bool synchronous
>  	struct intel_fbdev *ifbdev = dev_priv->fbdev;
>  	struct fb_info *info;
>  
> +	async_synchronize_full();
>  	if (!ifbdev)
>  		return;
>  
> @@ -800,6 +801,8 @@ void intel_fbdev_set_suspend(struct drm_device *dev, int state, bool synchronous
>  void intel_fbdev_output_poll_changed(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> +
> +	async_synchronize_full();
>  	if (dev_priv->fbdev)
>  		drm_fb_helper_hotplug_event(&dev_priv->fbdev->helper);
>  }
> @@ -811,6 +814,7 @@ void intel_fbdev_restore_mode(struct drm_device *dev)
>  	struct intel_fbdev *ifbdev = dev_priv->fbdev;
>  	struct drm_fb_helper *fb_helper;
>  
> +	async_synchronize_full();
>  	if (!ifbdev)
>  		return;
>  
> -- 
> 1.8.5.2 (Apple Git-48)
> 


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