[Intel-gfx] [PATCH i-g-t 3/3] i915/gem_exec_fence: Avoid long preempt-off sleeps

[Tvrtko Ursulin]

On 08/11/2019 14:22, Chris Wilson wrote:
> The kernel is now enforcing that clients are not allowed to block higher
> priority contexts from accessing the GPU; one is no longer allowed to
> sleep for a second hogging the GPU. Reduce the sleep down to 50ms, short
> enough not to anger the preempt-off checks while long enough for any
> ordinary GPU work to complete.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>   tests/i915/gem_exec_fence.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/i915/gem_exec_fence.c b/tests/i915/gem_exec_fence.c
> index 4e8bdd7b3..002120bf3 100644
> --- a/tests/i915/gem_exec_fence.c
> +++ b/tests/i915/gem_exec_fence.c
> @@ -348,7 +348,8 @@ static void test_fence_await(int fd, unsigned ring, unsigned flags)
>   		i++;
>   	}
>   
> -	sleep(1);
> +	/* Long, but not too long to anger preemption disable checks */
> +	usleep(50 * 1000); /* 50 ms, typical preempt reset is 150+ms */

Was the point of this sleep two-fold: 1) allow spinner to start (use 
polling spinner?) and allow forked children to submit (use pipe sync?)?

But okay as a quick fix.

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

Regards,

Tvrtko

>   
>   	/* Check for invalidly completing the task early */
>   	igt_assert(fence_busy(spin->out_fence));
>