[Intel-gfx] [PATCH v4 15/16] drm/i915: Immediately process a reset before starting waiting

[Tvrtko Ursulin]

On 23/02/2017 12:41, Chris Wilson wrote:
> On Thu, Feb 23, 2017 at 12:35:38PM +0000, Tvrtko Ursulin wrote:
>>
>> On 23/02/2017 07:44, Chris Wilson wrote:
>>> As we handoff the GPU reset to the waiter, we need to check we don't
>>> miss a wakeup if it has already been sent prior to us starting the wait.
>>>
>>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> ---
>>> drivers/gpu/drm/i915/i915_gem_request.c | 7 +++++--
>>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
>>> index ee601e13e28a..eaa333a35f7c 100644
>>> --- a/drivers/gpu/drm/i915/i915_gem_request.c
>>> +++ b/drivers/gpu/drm/i915/i915_gem_request.c
>>> @@ -1081,8 +1081,10 @@ long i915_wait_request(struct drm_i915_gem_request *req,
>>> 	trace_i915_gem_request_wait_begin(req, flags);
>>>
>>> 	add_wait_queue(&req->execute, &exec);
>>> -	if (flags & I915_WAIT_LOCKED)
>>> +	if (flags & I915_WAIT_LOCKED) {
>>> 		add_wait_queue(errq, &reset);
>>> +		__i915_wait_request_check_and_reset(req);
>>> +	}
>>>
>>> 	intel_wait_init(&wait);
>>>
>>> @@ -1120,7 +1122,8 @@ long i915_wait_request(struct drm_i915_gem_request *req,
>>> 		goto complete;
>>>
>>> 	set_current_state(state);
>>> -	if (intel_engine_add_wait(req->engine, &wait))
>>> +	if (intel_engine_add_wait(req->engine, &wait) ||
>>> +	    flags & I915_WAIT_LOCKED)
>>> 		/* In order to check that we haven't missed the interrupt
>>> 		 * as we enabled it, we need to kick ourselves to do a
>>> 		 * coherent check on the seqno before we sleep.
>>>
>>
>> Didn't figure this second bit - what's happening here?
>
> As we are now on the error/reset waitqueue from the start and have just
> set ourselves back to TASK_INTERRUPTIBLE (overriding any wake up from
> reset) before we actually sleep we need to double check for the signal
> from i915_reset.

Makes sense yes.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko