Re: [PATCH] drm/i915: Pull intel_uncore_arm_unclaimed_mmio_detection() under the spinlock

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Elsewhere we manipulate uncore.unclaimed_mmio_check and
> i915_param.mmio_debug under the irq lock (e.g. preserving the current
> value across a user forcewake grab), but do not protect the manipulation
> inside intel_uncore_arm_unclaimed_mmio_detection() from concurrent
> access, even from itself. This is an issue as we do call
> arm_unclaimed_mmio_detection from multiple threads without coordination.
>
> Suggested-by: Mika Kuoppala <mika.kuoppala@intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_uncore.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index 05f0cda18501..3ad302c66254 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -2283,8 +2283,12 @@ bool intel_uncore_unclaimed_mmio(struct drm_i915_private *dev_priv)
>  bool
>  intel_uncore_arm_unclaimed_mmio_detection(struct drm_i915_private *dev_priv)
>  {
> +	bool ret = false;
> +
> +	spin_lock_irq(&dev_priv->uncore.lock);
> +
>  	if (unlikely(dev_priv->uncore.unclaimed_mmio_check <= 0))
> -		return false;
> +		goto out;
>  
>  	if (unlikely(intel_uncore_unclaimed_mmio(dev_priv))) {
>  		if (!i915_modparams.mmio_debug) {
> @@ -2294,10 +2298,13 @@ intel_uncore_arm_unclaimed_mmio_detection(struct drm_i915_private *dev_priv)
>  			i915_modparams.mmio_debug++;
>  		}
>  		dev_priv->uncore.unclaimed_mmio_check--;
> -		return true;
> +		ret = true;
>  	}
>  
> -	return false;
> +out:
> +	spin_unlock_irq(&dev_priv->uncore.lock);
> +
> +	return ret;

Patchbot didn't see how the future will unfold. I did.

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intelcom>

>  }
>  
>  static enum forcewake_domains
> -- 
> 2.19.0.rc1
>
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