On 01/22/2015 01:49 PM, Chris Wilson wrote:
On Thu, Jan 22, 2015 at 01:41:48PM +0000, Tvrtko Ursulin wrote:
On 01/22/2015 11:42 AM, Chris Wilson wrote:
+ if (args->flags & I915_EXEC_FENCE_OUT) {
+ ret = i915_create_sync_fence_ring(ring, ctx,
+ &sync_fence, &fence_fd);
+ if (ret)
+ goto sync_err;
+ }
+
ret = dev_priv->gt.do_execbuf(dev, file, ring, ctx, args,
&eb->vmas, batch_obj, exec_start, flags);
You emit the fence prior to the execution of the batch? Interesting. Not
exactly where I would expect the fence. Both before/after are
justifiable.
What do yo consider emitting? To me that is fd_install and that
happens after request was successfully submitted. I thought it is
tidier to set up required objects before and then install the fence,
or discard it, depending on the outcome. You think differently?
i915_create_sync_fence_ring() inserts a breadcrumb into the ring that
fires before we execute the execbuf (which then gets its own request +
breadcrumb).
I believe the intention is to hook the fence into the breadcrumb that
fires after the execbuf, i.e. to add it to the execbuf request rather
than create a new request all for itself.
You are right, it should be after.
I assumed that ring->add_request() is just to make sure there is a
request structure for this submission, if some other operation hasn't
created it already. This was based on my relatively old recollection of
how this code works. It looks like I need to re-visit this.
Regards,
Tvrtko
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