From cb98e37357b03ce078d859a78ec603e7797bc931 Mon Sep 17 00:00:00 2001 From: Simon McVittie Date: Mon, 18 Dec 2017 10:47:29 +0000 Subject: [PATCH] closures test: Avoid timeout on ARM64 CPUs Closures use a 16-bit atomic reference count, which is really slow on certain ARM64 CPUs such as the Cortex-A57 (glib#1316). This is non-trivial to solve, since the public struct field cannot be enlarged to 32-bit while preserving ABI, and 16-bit atomic operations would be new (and rather niche) API. Until this can be solved properly (hopefully in GLib 2.59.x), cut down the number of signal emission cycles and bump up the timeout in the Meson build system, so that builds won't time out. We can't just take another zero off the number of signal emission cycles, as was done in the original version of this patch in Debian, because if we do that it can result in test failures when the main thread starves the other threads. ARM64 CPUs are backwards-compatible with 32-bit ARM, and the same slowdown can be seen when building and testing 32-bit code on these CPUs, so check for both 32- and 64-bit ARM. Bug-Debian: https://bugs.debian.org/880883 Co-authored-by: Iain Lane Signed-off-by: Simon McVittie --- tests/refcount/closures.c | 12 ++++++++++++ tests/refcount/meson.build | 7 +++++++ 2 files changed, 19 insertions(+) diff --git a/tests/refcount/closures.c b/tests/refcount/closures.c index 25b0a2779..188406786 100644 --- a/tests/refcount/closures.c +++ b/tests/refcount/closures.c @@ -259,7 +259,19 @@ main (int argc, thread1 = g_thread_create (thread1_main, closure, TRUE, NULL); thread2 = g_thread_create (thread2_main, closure, TRUE, NULL); + /* The 16-bit compare-and-swap operations currently used for closure + * refcounts are really slow on some ARM CPUs, notably Cortex-A57. + * Reduce the number of iterations so that the test completes in a + * finite time, but don't reduce it so much that the main thread + * starves the other threads and causes a test failure. + * + * https://gitlab.gnome.org/GNOME/glib/issues/1316 + * aka https://bugs.debian.org/880883 */ +#if defined(__aarch64__) || defined(__arm__) + for (i = 0; i < 100000; i++) +#else for (i = 0; i < 1000000; i++) +#endif { static guint count = 0; test_emissions (object); diff --git a/tests/refcount/meson.build b/tests/refcount/meson.build index 68c23cc41..22b9655d7 100644 --- a/tests/refcount/meson.build +++ b/tests/refcount/meson.build @@ -54,6 +54,13 @@ foreach test_name, extra_args : refcount_tests suite = ['refcount'] + extra_args.get('suite', []) timeout = suite.contains('slow') ? test_timeout_slow : test_timeout + + # https://gitlab.gnome.org/GNOME/glib/issues/1316 + # aka https://bugs.debian.org/880883 + if test_name == 'closures' and ['arm', 'aarch64'].contains(host_cpu_family) + timeout = timeout * 10 + endif + # FIXME? TESTS_ENVIRONMENT = LIBCHARSET_ALIAS_DIR=$(top_builddir)/glib/libcharset test(test_name, exe, env : test_env, timeout : timeout, suite : suite) endforeach