tests: tighten memory_ipc outer timeout to CHILD_TIMEOUT_SEC + 30

The previous 3 * CHILD_TIMEOUT_SEC scaling assumed worst-case wall-clock
where every sequential join/wait hits its full timeout. In practice the
children run concurrently, so expected wall-clock is ~CHILD_TIMEOUT_SEC
regardless of how many joins the test chains -- once a child is done its
join returns immediately. Exceeding CHILD_TIMEOUT_SEC + slack already
means something is genuinely stuck, in which case the outer guard firing
is the right outcome; the autouse track_child_processes() context
manager still cleans up survivors, and the per-test diagnostic message
would not be more informative than "test exceeded its budget".

New budgets:
- Without compute-sanitizer:  60 s (was 90 s).
- Under compute-sanitizer:   150 s (was 360 s).

The meta-test computes its expected value from the same formula.

Author: Andy-Jost

cuda_core/tests/memory_ipc/conftest.py

@@ -19,13 +19,15 @@
 
 
 def _outer_timeout_sec() -> int:
-    # The worst-case IPC test has three sequential CHILD_TIMEOUT_SEC waits in
-    # the failure path (e.g. TestIpcReexport: event_c.wait, proc_b.join,
-    # proc_c.join). Scaling by 3 lets such a test reach its own asserts before
-    # the outer guard fires, while still cutting the budget by half on
-    # non-sanitizer runs (90 s vs the previous 300 s) and scaling up under
-    # compute-sanitizer (360 s).
-    return 3 * child_timeout_sec()
+    # IPC tests spawn children that run concurrently, so expected wall-clock
+    # is ~CHILD_TIMEOUT_SEC regardless of how many subsequent join/wait
+    # timeouts the test chains together (each subsequent join returns
+    # immediately once its child is already done). Exceeding that already
+    # means something is genuinely stuck, at which point the outer guard
+    # firing is the right outcome -- the per-test asserts wouldn't add
+    # useful diagnostic value over "test exceeded its budget", and the
+    # autouse track_child_processes() context manager still cleans up.
+    return child_timeout_sec() + 30
 
 
 def pytest_collection_modifyitems(config, items):

cuda_core/tests/memory_ipc/test_errors.py

@@ -25,7 +25,7 @@ def test_outer_timeout_marker_is_applied(request):
     the in-test cleanup -- which we want to keep as defense in depth, not as
     the sole guard.
     """
-    expected = 3 * child_timeout_sec()
+    expected = child_timeout_sec() + 30
     marker = request.node.get_closest_marker("timeout")
     assert marker is not None, "memory_ipc/conftest.py did not apply a timeout marker"
     assert marker.args == (expected,), f"unexpected timeout value: {marker.args!r}"