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

[Chris Wilson <chris@chris-wilson.co.uk>]

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.

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 | 30 +++++++++-----------------
 1 file changed, 10 insertions(+), 20 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..f171db16a1c4 100644
--- a/drivers/gpu/drm/i915/selftests/i915_sw_fence.c
+++ b/drivers/gpu/drm/i915/selftests/i915_sw_fence.c
@@ -661,7 +661,7 @@ static int test_dma_fence(void *arg)
 {
 	struct i915_sw_fence *timeout = NULL, *not = NULL;
 	unsigned long delay = i915_selftest.timeout_jiffies;
-	unsigned long end, sleep;
+	unsigned long start, end;
 	struct dma_fence *dma;
 	int err;
 
@@ -688,36 +688,26 @@ static int test_dma_fence(void *arg)
 	}
 
 	/* We round the timeout for the fence up to the next second */
-	end = round_jiffies_up(jiffies + delay);
+	start = jiffies;
+	end = round_jiffies_up(start + delay);
 
-	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);
-		goto skip;
+	if (wait_event_interruptible(timeout->wait,
+				     i915_sw_fence_done(timeout))) {
+		err = -EINTR;
+		goto err;
 	}
 
-	if (i915_sw_fence_done(timeout) || i915_sw_fence_done(not)) {
-		pr_err("Fences signaled too early\n");
+	if (time_after(jiffies, 2*end - start)) {
+		pr_err("Timeout (now %lu) later than expected (%lu)\n",
+		       jiffies, end);
 		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");
 		goto err;
 	}
 
-	if (!i915_sw_fence_done(timeout)) {
-		pr_err("Timeout fence unsignaled!\n");
-		goto err;
-	}
-
-skip:
 	dma_fence_signal(dma);
 
 	if (!i915_sw_fence_done(timeout) || !i915_sw_fence_done(not)) {
-- 
2.15.1

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