[PATCH i-g-t] tests/sw_sync: Add subtest test_sync_expired_merge

[Rafael Antognolli]

This test creates an already expired fence, then creates a merged fence
out of that expired one (passed twice to the merge operation), and
finally closes the merged fence. It shows that if the refcounts are
wrong on the original expired fence, it might get freed while still in
use. Usually a kernel panick will follow.

Signed-off-by: Rafael Antognolli <rafael.antognolli at intel.com>
---
 tests/sw_sync.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tests/sw_sync.c b/tests/sw_sync.c
index 4336659..31cde50 100644
--- a/tests/sw_sync.c
+++ b/tests/sw_sync.c
@@ -582,6 +582,31 @@ static void test_sync_multi_producer_single_consumer(void)
 		pthread_join(threads[i], NULL);
 }
 
+static void test_sync_expired_merge(void)
+{
+	int iterations = 1 << 20;
+	int timeline;
+	int i;
+	int fence_expired, fence_merged;
+
+	timeline = sw_sync_timeline_create();
+
+	sw_sync_timeline_inc(timeline, 100);
+	fence_expired = sw_sync_fence_create(timeline, 1);
+	fence_merged = sw_sync_merge(fence_expired, fence_expired);
+	sw_sync_fence_destroy(fence_merged);
+
+	for (i = 0; i < iterations; i++) {
+		int fence = sw_sync_merge(fence_expired, fence_expired);
+
+		igt_assert_f(sw_sync_wait(fence, -1) > 0,
+				     "Failure waiting on fence\n");
+		sw_sync_fence_destroy(fence);
+	}
+
+	sw_sync_fence_destroy(fence_expired);
+}
+
 static void test_sync_random_merge(void)
 {
 	int i, size, ret;
@@ -687,6 +712,9 @@ igt_main
 	igt_subtest("sync_multi_producer_single_consumer")
 		test_sync_multi_producer_single_consumer();
 
+	igt_subtest("sync_expired_merge")
+		test_sync_expired_merge();
+
 	igt_subtest("sync_random_merge")
 		test_sync_random_merge();
 }
-- 
2.7.4