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

[Chris Wilson]

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.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre