perf tests sigtrap: Skip if running on a kernel with sleepable spinlocks

There are issues as reported that need some more investigation on the
RT kernel front, till that is addressed, skip this test.

This test is already skipped for multiple hardware architectures where
the tested kernel feature is not supported.

Acked-by: Marco Elver <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Clark Williams <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Juri Lelli <[e-mail]>
Cc: Kate Carcia <[e-mail]>
Cc: Marco Elver <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Link: https://lore.kernel.org/all/[e-mail]/
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/sigtrap.c

···
 
 	return __btf_type__find_member_by_name(id, "sigtrap") != NULL;
 }
+
+static bool kernel_with_sleepable_spinlocks(void)
+{
+	const struct btf_member *member;
+	const struct btf_type *type;
+	const char *type_name;
+	int id;
+
+	if (!btf__available())
+		return false;
+
+	id = btf__find_by_name_kind(btf, "spinlock", BTF_KIND_STRUCT);
+	if (id < 0)
+		return false;
+
+	// Only RT has a "lock" member for "struct spinlock"
+	member = __btf_type__find_member_by_name(id, "lock");
+	if (member == NULL)
+		return false;
+
+	// But check its type as well
+	type = btf__type_by_id(btf, member->type);
+	if (!type || !btf_is_struct(type))
+		return false;
+
+	type_name = btf__name_by_offset(btf, type->name_off);
+	return type_name && !strcmp(type_name, "rt_mutex_base");
+}
 #else  /* !HAVE_BPF_SKEL */
 static bool attr_has_sigtrap(void)
 {
···
 	}
 
 	return ret;
+}
+
+static bool kernel_with_sleepable_spinlocks(void)
+{
+	return false;
 }
 
 static void btf__exit(void)
···
 
 static int run_stress_test(int fd, pthread_t *threads, pthread_barrier_t *barrier)
 {
-	int ret;
+	int ret, expected_sigtraps;
 
 	ctx.iterate_on = 3000;
 
···
 	ret = run_test_threads(threads, barrier);
 	TEST_ASSERT_EQUAL("disable failed", ioctl(fd, PERF_EVENT_IOC_DISABLE, 0), 0);
 
-	TEST_ASSERT_EQUAL("unexpected sigtraps", ctx.signal_count, NUM_THREADS * ctx.iterate_on);
+	expected_sigtraps = NUM_THREADS * ctx.iterate_on;
+
+	if (ctx.signal_count < expected_sigtraps && kernel_with_sleepable_spinlocks()) {
+		pr_debug("Expected %d sigtraps, got %d, running on a kernel with sleepable spinlocks.\n",
+			 expected_sigtraps, ctx.signal_count);
+		pr_debug("See https://lore.kernel.org/all/[e-mail]/\n");
+		return TEST_SKIP;
+	} else
+		TEST_ASSERT_EQUAL("unexpected sigtraps", ctx.signal_count, expected_sigtraps);
+
 	TEST_ASSERT_EQUAL("missing signals or incorrectly delivered", ctx.tids_want_signal, 0);
 	TEST_ASSERT_VAL("unexpected si_addr", ctx.first_siginfo.si_addr == &ctx.iterate_on);
 #if 0 /* FIXME: enable when libc's signal.h has si_perf_{type,data} */