[Intel-gfx] [PATCH v8 4/6] drm/i915: Interrupt driven fences

[John Harrison]

On 13/05/2016 08:27, Chris Wilson wrote:
> On Thu, May 12, 2016 at 10:06:34PM +0100, John.C.Harrison at Intel.com wrote:
>> +void i915_gem_request_notify(struct intel_engine_cs *engine, bool fence_locked)
>> +{
>> +	struct drm_i915_gem_request *req, *req_next;
>> +	unsigned long flags;
>>   	u32 seqno;
>>   
>> -	seqno = req->engine->get_seqno(req->engine);
>> +	if (list_empty(&engine->fence_signal_list))
>> +		return;
>> +
>> +	if (!fence_locked)
>> +		spin_lock_irqsave(&engine->fence_lock, flags);
>> +
>> +	if (engine->irq_seqno_barrier)
>> +		engine->irq_seqno_barrier(engine);
>> +	seqno = engine->get_seqno(engine);
>> +
>> +	list_for_each_entry_safe(req, req_next, &engine->fence_signal_list, signal_link) {
> NO, NO, NO. As we said the very first time, you cannot do this from an
> irq handler.
>
> The current code is already bad enough, this is making it large constant
> + N times worse. Please do look at how to do signal driven fences in O(1)
> that I posted many months ago and several times since.

If you have a better solution available then please post it in a form 
that can be merged and get it reviewed and accepted.

> -Chris
>