Re: [PATCH] drm/i915: Don't del_timer_sync uninitialized timer

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Mar 17, 2014 at 01:17:32PM +0000, Chris Wilson wrote:
> On Sat, Mar 15, 2014 at 11:30:18AM -0700, Ben Widawsky wrote:
> > On Sat, Mar 15, 2014 at 03:20:23PM +0000, Chris Wilson wrote:
> > > On Sat, Mar 15, 2014 at 12:47:22PM +0100, Daniel Vetter wrote:
> > > > On Fri, Mar 14, 2014 at 05:21:36PM -0700, Ben Widawsky wrote:
> > > > > Broken by:
> > > > > commit 0294ae7b44bba7ab0d4cef9a8736287f38bdb4fd
> > > > > Author: Chris Wilson <chris@chris-wilson.co.uk>
> > > > > Date:   Thu Mar 13 12:00:29 2014 +0000
> > > > > 
> > > > >     drm/i915: Consolidate forcewake resetting to a single function
> > > > > 
> > > > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > > > Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> > > > > Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> > > > > ---
> > > > >  drivers/gpu/drm/i915/intel_uncore.c | 6 +++---
> > > > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> > > > > index e6bb421..7e55ceb 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_uncore.c
> > > > > +++ b/drivers/gpu/drm/i915/intel_uncore.c
> > > > > @@ -362,6 +362,9 @@ void intel_uncore_early_sanitize(struct drm_device *dev)
> > > > >  {
> > > > >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > > > >  
> > > > > +	setup_timer(&dev_priv->uncore.force_wake_timer,
> > > > > +		    gen6_force_wake_timer, (unsigned long)dev_priv);
> > > > 
> > > > We call early_sanitize also from our resume code, so this will now
> > > > re-setup the timer again. We generally don't do that since if we ever leak
> > > > the timer to here in an enabled state it causes havoc.
> > > 
> > > Gah, really? intel_uncore_early_init()! There must be a clean way to
> > > break this up.
> > > -Chris
> > 
> > At least in the code base I was looking at, we currently do this also,
> > so I didn't think this was any worse.
> > 
> > With lockdep turned on, the module will not even load, so please either
> > revert the original, or merge this.
> 
> I think we can just:
> 
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index a62ff21..c9fcc20 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -317,9 +317,10 @@ static void intel_uncore_forcewake_reset(struct drm_device *dev, bool restore)
>  {
>         struct drm_i915_private *dev_priv = dev->dev_private;
>         unsigned long irqflags;
> -       int pending;
> +       int pending = 0;
>  
> -       pending = del_timer_sync(&dev_priv->uncore.force_wake_timer);
> +       if (dev_priv->uncore.force_wake_timer.function)
> +               pending = del_timer_sync(&dev_priv->uncore.force_wake_timer);
>  
>         /* Hold uncore.lock across reset to prevent any register access
>          * with forcewake not set correctly
> 
> i.e.
> 
> -       del_timer_sync(&dev_priv->uncore.force_wake_timer);
> +       if (dev_priv->uncore.force_wake_timer.function)
> +               del_timer_sync(&dev_priv->uncore.force_wake_timer);

I've thought of this:

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index e4d2b9f15ae2..9faee49f210d 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1608,8 +1608,6 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 		goto put_bridge;
 	}
 
-	intel_uncore_early_sanitize(dev);
-
 	/* This must be called before any calls to HAS_PCH_* */
 	intel_detect_pch(dev);
 
diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index e2e328d86aff..c3832d9270a6 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -736,6 +736,8 @@ void intel_uncore_init(struct drm_device *dev)
 	setup_timer(&dev_priv->uncore.force_wake_timer,
 		    gen6_force_wake_timer, (unsigned long)dev_priv);
 
+	intel_uncore_early_sanitize(dev);
+
 	if (IS_VALLEYVIEW(dev)) {
 		dev_priv->uncore.funcs.force_wake_get = __vlv_force_wake_get;
 		dev_priv->uncore.funcs.force_wake_put = __vlv_force_wake_put;

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