[PATCH 1/2] drm/sched: add drm_sched_prealloc_dependency_slots

[Christian König]

>> + *
>> + * Return:
>> + * 0 on success, or an error on failing to expand the array.
>> + */
>> +int drm_sched_job_prealloc_dependency_slots(struct drm_sched_job
>> *job,
>> +					    unsigned int num_deps)
>> +{
>> +	struct dma_fence *fence;
>> +	u32 id = 0;
>> +	int ret;
>> +
>> +	while (num_deps--) {
>> +		fence = dma_fence_get_stub();
>> +		ret = xa_alloc(&job->dependencies, &id, fence,
>> xa_limit_32b,
>> +			       GFP_KERNEL);
> So this would fill the xarr with already signaled fences which then
> later will be replaced with unsignaled fences?

Yes, exactly that's the idea.

> Help me out here: would it also work to add NULL instead of that stub-
> fence?

Good question, idk. That's an implementation detail of the xarray.

Tvrtko also correctly pointed out that it is most likely a bad idea to use dma_fence_is_signaled() in the critical code path.

I will try to dig through the xarray behavior up and update the patch if possible.

Thanks,
Christian.
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