The scheduler may use a semaphore between engines to serialise requests,
and in doing so submit the request before its signalers are ready. This
dependency must also be copied across any SUBMIT_FENCE so that a
bonded-pair will not execute ahead of any of its implicit dependencies
-- it too must wait for the same semaphores.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
tests/i915/gem_exec_balancer.c | 104 +++++++++++++++++++++++++++++++++
1 file changed, 104 insertions(+)
diff --git a/tests/i915/gem_exec_balancer.c b/tests/i915/gem_exec_balancer.c
index e5e83508f..5f6e3d568 100644
--- a/tests/i915/gem_exec_balancer.c
+++ b/tests/i915/gem_exec_balancer.c
@@ -959,6 +959,107 @@ static void bonded_chain(int i915)
gem_context_destroy(i915, ctx);
}
+static void __bonded_sema(int i915, uint32_t ctx,
+ const struct i915_engine_class_instance *siblings,
+ unsigned int count)
+{
+ const int priorities[] = { -1023, 0, 1023 };
+ struct drm_i915_gem_exec_object2 batch = {
+ .handle = batch_create(i915),
+ };
+ struct drm_i915_gem_execbuffer2 execbuf = {
+ .buffers_ptr = to_user_pointer(&batch),
+ .buffer_count = 1,
+ .rsvd1 = ctx,
+ };
+ igt_spin_t *spin;
+
+ for (int i = 0; i < ARRAY_SIZE(priorities); i++) {
+ /* A: spin forever on seperate render engine */
+ spin = igt_spin_new(i915,
+ .flags = (IGT_SPIN_POLL_RUN |
+ IGT_SPIN_FENCE_OUT));
+ igt_spin_busywait_until_started(spin);
+
+ /*
+ * Note we replace the timelines between each execbuf, so
+ * that any pair of requests on the same engine could be
+ * re-ordered by the scheduler -- if the dependency tracking
+ * is subpar.
+ */
+
+ /* B: waits for A (using a semaphore) on engine 1 */
+ set_load_balancer(i915, ctx, siblings, count, NULL);
+ execbuf.rsvd2 = spin->out_fence;
+ execbuf.flags = I915_EXEC_FENCE_IN | I915_EXEC_FENCE_OUT;
+ execbuf.flags |= 1;
+ gem_execbuf_wr(i915, &execbuf);
+
+ /* B': run in parallel with B on engine 2 */
+ if (priorities[i] > 0)
+ gem_context_set_priority(i915, ctx, priorities[i]);
+ set_load_balancer(i915, ctx, siblings, count, NULL);
+ execbuf.flags = I915_EXEC_FENCE_SUBMIT | I915_EXEC_FENCE_OUT;
+ execbuf.flags |= 2;
+ execbuf.rsvd2 >>= 32;
+ gem_execbuf_wr(i915, &execbuf);
+ gem_context_set_priority(i915, ctx, 0);
+
+ /* Wait for any magic timeslicing or preemptions... */
+ igt_assert_eq(sync_fence_wait(execbuf.rsvd2 >> 32, 1000),
+ -ETIME);
+
+ igt_debugfs_dump(i915, "i915_engine_info");
+
+ /*
+ * ... which should not have happened, so everything is still
+ * waiting on the spinner
+ */
+ igt_assert_eq(sync_fence_status(spin->out_fence), 0);
+ igt_assert_eq(sync_fence_status(execbuf.rsvd2 & 0xffffffff), 0);
+ igt_assert_eq(sync_fence_status(execbuf.rsvd2 >> 32), 0);
+
+ igt_spin_free(i915, spin);
+ gem_sync(i915, batch.handle);
+
+ igt_assert_eq(sync_fence_status(execbuf.rsvd2 & 0xffffffff), 1);
+ igt_assert_eq(sync_fence_status(execbuf.rsvd2 >> 32), 1);
+
+ close(execbuf.rsvd2);
+ close(execbuf.rsvd2 >> 32);
+ }
+
+ gem_close(i915, batch.handle);
+}
+
+static void bonded_semaphore(int i915)
+{
+ uint32_t ctx;
+
+ /*
+ * Given batches A, B and B', where B and B' are a bonded pair, with
+ * B' depending on B with a submit fence and B depending on A as
+ * an ordinary fence; prove B' cannot complete before A, with the
+ * difference here (wrt bonded_chain) that A is on another engine and
+ * so A, B and B' are expected to be inflight concurrently.
+ */
+ igt_require(gem_scheduler_has_semaphores(i915));
+
+ ctx = gem_context_create(i915);
+
+ for (int class = 1; class < 32; class++) {
+ struct i915_engine_class_instance *siblings;
+ unsigned int count;
+
+ siblings = list_engines(i915, 1u << class, &count);
+ if (count > 1)
+ __bonded_sema(i915, ctx, siblings, count);
+ free(siblings);
+ }
+
+ gem_context_destroy(i915, ctx);
+}
+
static void indices(int i915)
{
I915_DEFINE_CONTEXT_PARAM_ENGINES(engines, I915_EXEC_RING_MASK + 1);
@@ -1685,6 +1786,9 @@ igt_main
igt_subtest("bonded-chain")
bonded_chain(i915);
+ igt_subtest("bonded-semaphore")
+ bonded_semaphore(i915);
+
igt_fixture {
igt_stop_hang_detector();
}
--
2.24.0
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