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

[Damien Lespiau <damien.lespiau@intel.com>]

Hi Lukas,

I'm sorry I haven't reacted sooner. I've enabled the option to only
consider git send-email patches on intel-gfx as we were having a lot of
false positives (ie patchwork considering emails were people were making
suggestions with diffs as patches to test).

I'm not sure how you send your emails, but I can tell why that it didn't
pass the "is this a git send-email patch?" question. We're looking at
two things:

  - The X-Mailer header
  - The Message-Id (git send-email has a special way to craft its
    message IDs)

I've replayed your email by hand with an extra X-Mailer header and
patchwork picked it up (and hopefully we should have a run of our basic
acceptance tests done on it):

  https://patchwork.freedesktop.org/series/4068/

You can keep whatever you're doing now and trick patchwork to take your
patches by added this extra header to your emails:

  X-Mailer: git-send-email 2.4.3

Or use git send-email.

HTH,

-- 
Damien

On Thu, Mar 03, 2016 at 07:30:33PM +0100, Lukas Wunner 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.
> 
> 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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