Re: [RFC i-g-t v2] tests/gem_exec_pad_to_size: Test object padding at execbuf

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 04/01/2015 02:56 PM, Chris Wilson wrote:
> On Wed, Apr 01, 2015 at 02:36:29PM +0100, Tvrtko Ursulin wrote:
>>
>> On 04/01/2015 02:06 PM, Chris Wilson wrote:
>>> On Wed, Apr 01, 2015 at 12:21:14PM +0100, Tvrtko Ursulin wrote:
>>>> +	if (drmIoctl(fd, DRM_IOCTL_I915_GEM_EXECBUFFER2, &execbuf))
>>>> +			ret = -errno;
>>>
>>>> +	if (ret == 0) {
>>>> +		gem_sync(fd, handles[0]);
>>> Not required for this test. However... You probably want to do the
>>> gem_sync() first. (Yes, there is an amusing reason to do :)
>>
>> What reason is that and what do you mean by "first"?
>
> When calling the test multiple times successive passes will have a busy
> batch, which could conceivably cause the relocations to fail, and the
> returned offsets to be -1. Calling gem_sync() before execbuf prevents that
> slowpath from affecting the test, without people wondering whether
> you need to call gem_sync() before the returned array is valid (which is
> why I did a double take here trying to work out what you meant the
> gem_sync() to do).

How it may be busy if gem_sync after execbuf is supposed to wait until 
batch has been retired?

Regards,

Tvrtko
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