Merge tag 'timers-urgent-2024-04-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fixes from Ingo Molnar:

 - Address a (valid) W=1 build warning

 - Fix timer self-tests

 - Annotate a KCSAN warning wrt. accesses to the tick_do_timer_cpu
   global variable

 - Address a !CONFIG_BUG build warning

* tag 'timers-urgent-2024-04-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  selftests: kselftest: Fix build failure with NOLIBC
  selftests: timers: Fix abs() warning in posix_timers test
  selftests: kselftest: Mark functions that unconditionally call exit() as __noreturn
  selftests: timers: Fix posix_timers ksft_print_msg() warning
  selftests: timers: Fix valid-adjtimex signed left-shift undefined behavior
  bug: Fix no-return-statement warning with !CONFIG_BUG
  timekeeping: Use READ/WRITE_ONCE() for tick_do_timer_cpu
  selftests/timers/posix_timers: Reimplement check_timer_distribution()
  irqflags: Explicitly ignore lockdep_hrtimer_exit() argument

1 files changed, 48 insertions, 57 deletions

diff --git a/tools/testing/selftests/timers/posix_timers.c b/tools/testing/selftests/timers/posix_timers.c
index d49dd3ffd0d9..c001dd79179d 100644
--- a/tools/testing/selftests/timers/posix_timers.c
+++ b/tools/testing/selftests/timers/posix_timers.c
@@ -66,7 +66,7 @@ static int check_diff(struct timeval start, struct timeval end)
 	diff = end.tv_usec - start.tv_usec;
 	diff += (end.tv_sec - start.tv_sec) * USECS_PER_SEC;
 
-	if (abs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
+	if (llabs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) {
 		printf("Diff too high: %lld..", diff);
 		return -1;
 	}
@@ -184,80 +184,71 @@ static int check_timer_create(int which)
 	return 0;
 }
 
-int remain;
-__thread int got_signal;
+static pthread_t ctd_thread;
+static volatile int ctd_count, ctd_failed;
 
-static void *distribution_thread(void *arg)
+static void ctd_sighandler(int sig)
 {
-	while (__atomic_load_n(&remain, __ATOMIC_RELAXED));
-	return NULL;
+	if (pthread_self() != ctd_thread)
+		ctd_failed = 1;
+	ctd_count--;
 }
 
-static void distribution_handler(int nr)
+static void *ctd_thread_func(void *arg)
 {
-	if (!__atomic_exchange_n(&got_signal, 1, __ATOMIC_RELAXED))
-		__atomic_fetch_sub(&remain, 1, __ATOMIC_RELAXED);
-}
-
-/*
- * Test that all running threads _eventually_ receive CLOCK_PROCESS_CPUTIME_ID
- * timer signals. This primarily tests that the kernel does not favour any one.
- */
-static int check_timer_distribution(void)
-{
-	int err, i;
-	timer_t id;
-	const int nthreads = 10;
-	pthread_t threads[nthreads];
 	struct itimerspec val = {
 		.it_value.tv_sec = 0,
 		.it_value.tv_nsec = 1000 * 1000,
 		.it_interval.tv_sec = 0,
 		.it_interval.tv_nsec = 1000 * 1000,
 	};
+	timer_t id;
 
-	remain = nthreads + 1;  /* worker threads + this thread */
-	signal(SIGALRM, distribution_handler);
-	err = timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
-	if (err < 0) {
-		ksft_perror("Can't create timer");
-		return -1;
-	}
-	err = timer_settime(id, 0, &val, NULL);
-	if (err < 0) {
-		ksft_perror("Can't set timer");
-		return -1;
-	}
+	/* 1/10 seconds to ensure the leader sleeps */
+	usleep(10000);
 
-	for (i = 0; i < nthreads; i++) {
-		err = pthread_create(&threads[i], NULL, distribution_thread,
-				     NULL);
-		if (err) {
-			ksft_print_msg("Can't create thread: %s (%d)\n",
-				       strerror(errno), errno);
-			return -1;
-		}
-	}
+	ctd_count = 100;
+	if (timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id))
+		return "Can't create timer\n";
+	if (timer_settime(id, 0, &val, NULL))
+		return "Can't set timer\n";
 
-	/* Wait for all threads to receive the signal. */
-	while (__atomic_load_n(&remain, __ATOMIC_RELAXED));
+	while (ctd_count > 0 && !ctd_failed)
+		;
 
-	for (i = 0; i < nthreads; i++) {
-		err = pthread_join(threads[i], NULL);
-		if (err) {
-			ksft_print_msg("Can't join thread: %s (%d)\n",
-				       strerror(errno), errno);
-			return -1;
-		}
-	}
+	if (timer_delete(id))
+		return "Can't delete timer\n";
 
-	if (timer_delete(id)) {
-		ksft_perror("Can't delete timer");
-		return -1;
-	}
+	return NULL;
+}
+
+/*
+ * Test that only the running thread receives the timer signal.
+ */
+static int check_timer_distribution(void)
+{
+	const char *errmsg;
 
-	ksft_test_result_pass("check_timer_distribution\n");
+	signal(SIGALRM, ctd_sighandler);
+
+	errmsg = "Can't create thread\n";
+	if (pthread_create(&ctd_thread, NULL, ctd_thread_func, NULL))
+		goto err;
+
+	errmsg = "Can't join thread\n";
+	if (pthread_join(ctd_thread, (void **)&errmsg) || errmsg)
+		goto err;
+
+	if (!ctd_failed)
+		ksft_test_result_pass("check signal distribution\n");
+	else if (ksft_min_kernel_version(6, 3))
+		ksft_test_result_fail("check signal distribution\n");
+	else
+		ksft_test_result_skip("check signal distribution (old kernel)\n");
 	return 0;
+err:
+	ksft_print_msg("%s", errmsg);
+	return -1;
 }
 
 int main(int argc, char **argv)