[igt-dev] [PATCH i-g-t v2 3/3] 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.
Those checks have been disabled, 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 starts, triggers a GPU hang and its fence is signaled.
With that in place, the test is able to check synchronously if execution
of dependent test batches is still blocked on the not yet signaled fence
of the not yet completed spin batch, as it does in counterpart non-hanging
scenarios.

v2: preserve checking the pipeline runs ahead of the hang (Chris)

Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
---
 tests/i915/gem_exec_fence.c | 41 ++++++++++++++++++++++++++++++-------
 1 file changed, 34 insertions(+), 7 deletions(-)

diff --git a/tests/i915/gem_exec_fence.c b/tests/i915/gem_exec_fence.c
index 78d83460f7..34f6b89337 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);
 			}
@@ -350,6 +365,16 @@ static void test_fence_await(int fd, const intel_ctx_t *ctx,
 	}
 
 	igt_spin_busywait_until_started(spin);
+	if (flags & HANG) {
+		igt_assert(fence_busy(spin->out_fence));
+		igt_fail_on(igt_spin_has_started(invalid_spin));
+		igt_assert(fence_busy(out_fence));
+		for (int n = 0; n <= i; n++)
+			igt_assert_eq_u32(out[n], 0);
+
+		igt_spin_end(spin);
+		igt_spin_busywait_until_started(invalid_spin);
+	}
 	/* Long, but not too long to anger preemption disable checks */
 	usleep(50 * 1000); /* 50 ms, typical preempt reset is 150+ms */
 
@@ -365,7 +390,7 @@ static void test_fence_await(int fd, const intel_ctx_t *ctx,
 	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 +398,8 @@ 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