Re: [PATCH] drm/i915: Don't continually defer the hangcheck

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Nov 07, 2014 at 05:14:36PM +0200, Mika Kuoppala wrote:
> Chris Wilson <chris@chris-wilson.co.uk> writes:
> 
> > On Fri, Nov 07, 2014 at 04:28:33PM +0200, Mika Kuoppala wrote:
> >> Chris Wilson <chris@chris-wilson.co.uk> writes:
> >> 
> >> > With multiple rings, we may continue to render on the blitter whilst
> >> > executing an infinite shader on the render ring. As we currently, rearm
> >> > the timer with each execbuf, in this scenario the hangcheck will never
> >> > fire and we will never detect the lockup on the render ring. Instead,
> >> > only arm the timer once per hangcheck, so that hangcheck runs more
> >> > frequently.
> >> >
> >> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> >> > Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> >> > ---
> >> >  drivers/gpu/drm/i915/i915_irq.c | 9 +++++++--
> >> >  1 file changed, 7 insertions(+), 2 deletions(-)
> >> >
> >> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> >> > index 318a6a0724d0..82b4d742aba5 100644
> >> > --- a/drivers/gpu/drm/i915/i915_irq.c
> >> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> >> > @@ -3039,11 +3039,16 @@ static void i915_hangcheck_elapsed(unsigned long data)
> >> >  void i915_queue_hangcheck(struct drm_device *dev)
> >> >  {
> >> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> >> > +	struct timer_list *timer = &dev_priv->gpu_error.hangcheck_timer;
> >> > +
> >> >  	if (!i915.enable_hangcheck)
> >> >  		return;
> >> >  
> >> > -	mod_timer(&dev_priv->gpu_error.hangcheck_timer,
> >> > -		  round_jiffies_up(jiffies + DRM_I915_HANGCHECK_JIFFIES));
> >> > +	if (timer_pending(timer))
> >> > +		return;
> >> > +
> >> 
> >> As this is called from both process and interrupt context, what
> >> keeps us safe from not messing up the timer bookkeepping? The lock in timer code?
> >> 
> >> I am thinking that the other thread will hit the BUG_ON in add_timer().
> >
> > if (!timer_pending(timer))
> > 	timer->expires = round_jiffies_up(jiffies + DRM_I915_HANGCHECK_JIFFIES));
> > mod_timer(timer, timer->expires);
> > ?
> 
> With this changed:
> 
> Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=86225

Can you please respin this with mod_timer so that I can slurp it in?

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