[PATCH i-g-t 3/5] tests/gem_exec_fence: Restore pre-hang checks in *await-hang scenarios

[Janusz Krzysztofik]

Commit c8f6aaf32d83 "tests/gem_exec_fence: Check stored values only for
valid workloads" resolved an issue, observed in *await-hang scenarios,
where a fence exposed by an invalid spin batch was signaled asynchronously
to pending checks for depended test batches still waiting for that fence,
by disabling those checks, then weakening those scenarios.  This change
takes an alternative approach: it makes the invalid spin batch dependent
on another fence so the test has full control over the moment when that
batch is executed, followed by GPU hang and its fence being signaled.
With that in place, the test is able to check synchronously if execution
of dependent test batches is blocked on the not yet signaled fence of the
not yet completed spin batch, the same way it does in counterpart non-hang
scenarios.

Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
---
 tests/i915/gem_exec_fence.c | 45 ++++++++++++++++++++++++++-----------
 1 file changed, 32 insertions(+), 13 deletions(-)

diff --git a/tests/i915/gem_exec_fence.c b/tests/i915/gem_exec_fence.c
index 11d99781b0..27af9718d9 100644
--- a/tests/i915/gem_exec_fence.c
+++ b/tests/i915/gem_exec_fence.c
@@ -309,10 +309,10 @@ static void test_fence_await(int fd, const intel_ctx_t *ctx,
 {
 	const struct intel_execution_engine2 *e2;
 	uint32_t scratch = gem_create(fd, 4096);
-	igt_spin_t *spin;
+	igt_spin_t *spin, *invalid_spin;
 	uint32_t *out;
 	uint64_t scratch_offset, ahnd = get_reloc_ahnd(fd, ctx->id);
-	int i;
+	int out_fence, i;
 
 	scratch_offset = get_offset(ahnd, scratch, 4096, 0);
 
@@ -325,10 +325,25 @@ static void test_fence_await(int fd, const intel_ctx_t *ctx,
 			    .ctx = ctx,
 			    .engine = e->flags,
 			    .flags = IGT_SPIN_FENCE_OUT |
-				     IGT_SPIN_POLL_RUN |
-				     spin_hang(flags));
+				     IGT_SPIN_POLL_RUN);
 	igt_assert(spin->out_fence != -1);
 
+	if (flags & HANG) {
+		invalid_spin = igt_spin_new(fd,
+					    .ahnd = ahnd,
+					    .ctx = ctx,
+					    .engine = e->flags,
+					    .fence = spin->out_fence,
+					    .flags = IGT_SPIN_FENCE_IN |
+						     IGT_SPIN_FENCE_OUT |
+						     IGT_SPIN_POLL_RUN |
+						     spin_hang(flags));
+		igt_assert(invalid_spin->out_fence != -1);
+		out_fence = invalid_spin->out_fence;
+	} else {
+		out_fence = spin->out_fence;
+	}
+
 	i = 0;
 	for_each_ctx_engine(fd, ctx, e2) {
 		if (!gem_class_can_store_dword(fd, e2->class))
@@ -337,12 +352,12 @@ static void test_fence_await(int fd, const intel_ctx_t *ctx,
 		i++;
 
 		if (flags & NONBLOCK) {
-			igt_store_word(fd, ahnd, ctx, e2, spin->out_fence,
+			igt_store_word(fd, ahnd, ctx, e2, out_fence,
 				       scratch, scratch_offset, i, i);
 		} else {
 			igt_fork(child, 1) {
 				ahnd = get_reloc_ahnd(fd, ctx->id);
-				igt_store_word(fd, ahnd, ctx, e2, spin->out_fence,
+				igt_store_word(fd, ahnd, ctx, e2, out_fence,
 					       scratch, scratch_offset, i, i);
 				put_ahnd(ahnd);
 			}
@@ -353,19 +368,21 @@ static void test_fence_await(int fd, const intel_ctx_t *ctx,
 	/* Long, but not too long to anger preemption disable checks */
 	usleep(50 * 1000); /* 50 ms, typical preempt reset is 150+ms */
 
-	if ((flags & HANG) == 0) {
-		/* Check for invalidly completing the task early */
+	/* Check for invalidly completing the task early */
+	if (flags & HANG) {
 		igt_assert(fence_busy(spin->out_fence));
-		for (int n = 1; n <= i; n++)
-			igt_assert_eq_u32(out[n], 0);
-
-		igt_spin_end(spin);
+		igt_fail_on(igt_spin_has_started(invalid_spin));
 	}
+	igt_assert(fence_busy(out_fence));
+	for (int n = 1; n <= i; n++)
+		igt_assert_eq_u32(out[n], 0);
+
+	igt_spin_end(spin);
 
 	igt_waitchildren();
 
 	gem_set_domain(fd, scratch, I915_GEM_DOMAIN_GTT, 0);
-	igt_assert(!fence_busy(spin->out_fence));
+	igt_assert(!fence_busy(out_fence));
 	if ((flags & HANG) == 0) {
 		do
 			igt_assert_eq_u32(out[i], i);
@@ -373,6 +390,8 @@ static void test_fence_await(int fd, const intel_ctx_t *ctx,
 	}
 	munmap(out, 4096);
 
+	if (flags & HANG)
+		igt_spin_free(fd, invalid_spin);
 	igt_spin_free(fd, spin);
 	gem_close(fd, scratch);
 	put_offset(ahnd, scratch);
-- 
2.25.1