Re: [PATCH RESEND FOR CI] drm/i915: Fix races on fbdev

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 03 Mar 2016, Lukas Wunner <lukas@wunner.de> wrote:
> 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.

git send-email is all it takes.

BR,
Jani.


>
> 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 Fägerlind <gustav.fagerlind@gmail.com>
>> Reported-by: "Li, Weinan Z" <weinan.z.li@intel.com>
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Lukas Wunner <lukas@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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-- 
Jani Nikula, Intel Open Source Technology Center
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