Re: [PATCH v4] drm/i915/selftests: Wait for the dma-fence timeout

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

On 17/01/2018 13:57, Chris Wilson wrote:
> When testing that the timeout fired, we need to be sure we have waited
> just long enough for the timeout to have occurred and for the softirq
> (on another cpu) to have completed. Sleeping for an arbitrary amount is
> prone to error, so wait for the timeout instead and complain if it was
> too late.
> 
> v2: Use wait_event_timeout to provide an upper bound
> v3: Fix inverted check for wait_event_timeout timing out
> v4: Restore the check that the fences aren't signalled too early, by
> inspecting them before the expected timeout.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=104670
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   drivers/gpu/drm/i915/selftests/i915_sw_fence.c | 18 ++++++++----------
>   1 file changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/selftests/i915_sw_fence.c b/drivers/gpu/drm/i915/selftests/i915_sw_fence.c
> index 4fb51deb81a1..570e325af93e 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_sw_fence.c
> +++ b/drivers/gpu/drm/i915/selftests/i915_sw_fence.c
> @@ -693,7 +693,8 @@ static int test_dma_fence(void *arg)
>   	sleep = jiffies_to_usecs(delay) / 3;
>   	usleep_range(sleep, 2 * sleep);
>   	if (time_after(jiffies, end)) {
> -		pr_debug("Slept too long, delay=%lu, skipping!\n", delay);
> +		pr_debug("Slept too long, delay=%lu, (target=%lu, now=%lu) skipping\n",
> +			 delay, end, jiffies);
>   		goto skip;
>   	}
>   
> @@ -702,18 +703,15 @@ static int test_dma_fence(void *arg)
>   		goto err;
>   	}
>   
> -	do {
> -		sleep = jiffies_to_usecs(end - jiffies + 1);
> -		usleep_range(sleep, 2 * sleep);
> -	} while (!time_after(jiffies, end));
> -
> -	if (i915_sw_fence_done(not)) {
> -		pr_err("No timeout fence signaled!\n");
> +	if (!wait_event_timeout(timeout->wait,
> +				i915_sw_fence_done(timeout),
> +				2 * (end - jiffies) + 1)) {
> +		pr_err("Timeout fence unsignaled!\n");
>   		goto err;
>   	}
>   
> -	if (!i915_sw_fence_done(timeout)) {
> -		pr_err("Timeout fence unsignaled!\n");
> +	if (i915_sw_fence_done(not)) {
> +		pr_err("No timeout fence signaled!\n");
>   		goto err;
>   	}
>   
> 

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

Regards,

Tvrtko
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