[Intel-gfx] [PATCH 12/46] drm/i915/gem: Track the rpm wakerefs

[John Harrison]

On 1/9/2019 03:16, Mika Kuoppala wrote:
> Chris Wilson <chris at chris-wilson.co.uk> writes:
>
>> diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
>> index 16693dd4d019..bc230e43b98f 100644
>> --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
>> +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
>> @@ -154,6 +154,7 @@ i915_gem_shrink(struct drm_i915_private *i915,
>>   		{ &i915->mm.bound_list, I915_SHRINK_BOUND },
>>   		{ NULL, 0 },
>>   	}, *phase;
>> +	intel_wakeref_t wakeref = 0;
>>   	unsigned long count = 0;
>>   	unsigned long scanned = 0;
>>   	bool unlock;
>> @@ -183,9 +184,11 @@ i915_gem_shrink(struct drm_i915_private *i915,
>>   	 * device just to recover a little memory. If absolutely necessary,
>>   	 * we will force the wake during oom-notifier.
>>   	 */
>> -	if ((flags & I915_SHRINK_BOUND) &&
>> -	    !intel_runtime_pm_get_if_in_use(i915))
>> -		flags &= ~I915_SHRINK_BOUND;
>> +	if (flags & I915_SHRINK_BOUND) {
>> +		wakeref = intel_runtime_pm_get_if_in_use(i915);
>> +		if (!wakeref)
>> +			flags &= ~I915_SHRINK_BOUND;
>> +	}
>>   
>>   	/*
>>   	 * As we may completely rewrite the (un)bound list whilst unbinding
>> @@ -266,7 +269,7 @@ i915_gem_shrink(struct drm_i915_private *i915,
>>   	}
>>   
>>   	if (flags & I915_SHRINK_BOUND)
>> -		intel_runtime_pm_put_unchecked(i915);
>> +		intel_runtime_pm_put(i915, wakeref);
> This is ok but raises a question that did we have
> GEM_BUG_ON(wakeref == 0) on pm_put? Perhaps not needed
> per se as we do find that we don't have ref for 0.
>
> Reviewed-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
>

There is a WARN not a BUG if pm_put() is called with a zero wakeref (in 
the cancel_ function after the search fails to find a match with zero). 
However, the flag checks mean that it can't happen from here.

John.