selftests/timers/posix-timers: Validate timer_gettime()

timer_gettime() must return the correct expiry time for interval timers
even when the timer is not armed, which is the case when a signal is
pending but blocked.

Works correctly for regular posix timers, but not for posix CPU timers.

Add a selftest to validate the fixes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

tools/testing/selftests/timers/posix_timers.c

@@ -487,10 +487,63 @@ static void check_sigev_none(int which, const char *name)
 			 "check_sigev_none %s\n", name);
 }
 
+static void check_gettime(int which, const char *name)
+{
+	struct itimerspec its, prev;
+	struct timespec start, now;
+	struct sigevent sev;
+	timer_t timerid;
+	int wraps = 0;
+	sigset_t set;
+
+	/* Block the signal */
+	sigemptyset(&set);
+	sigaddset(&set, SIGUSR1);
+	if (sigprocmask(SIG_BLOCK, &set, NULL))
+		fatal_error(name, "sigprocmask(SIG_BLOCK)");
+
+	memset(&sev, 0, sizeof(sev));
+	sev.sigev_notify = SIGEV_SIGNAL;
+	sev.sigev_signo = SIGUSR1;
+
+	if (timer_create(which, &sev, &timerid))
+		fatal_error(name, "timer_create()");
+
+	/* Start the timer to expire in 100ms and 100ms intervals */
+	its.it_value.tv_sec = 0;
+	its.it_value.tv_nsec = 100000000;
+	its.it_interval.tv_sec = 0;
+	its.it_interval.tv_nsec = 100000000;
+	if (timer_settime(timerid, 0, &its, NULL))
+		fatal_error(name, "timer_settime()");
+
+	if (timer_gettime(timerid, &prev))
+		fatal_error(name, "timer_gettime()");
+
+	if (clock_gettime(which, &start))
+		fatal_error(name, "clock_gettime()");
+
+	do {
+		if (clock_gettime(which, &now))
+			fatal_error(name, "clock_gettime()");
+		if (timer_gettime(timerid, &its))
+			fatal_error(name, "timer_gettime()");
+		if (its.it_value.tv_nsec > prev.it_value.tv_nsec)
+			wraps++;
+		prev = its;
+
+	} while (calcdiff_ns(now, start) < NSECS_PER_SEC);
+
+	if (timer_delete(timerid))
+		fatal_error(name, "timer_delete()");
+
+	ksft_test_result(wraps > 1, "check_gettime %s\n", name);
+}
+
 int main(int argc, char **argv)
 {
 	ksft_print_header();
-	ksft_set_plan(12);
+	ksft_set_plan(15);
 
 	ksft_print_msg("Testing posix timers. False negative may happen on CPU execution \n");
 	ksft_print_msg("based timers if other threads run on the CPU...\n");
@@ -518,6 +571,9 @@ int main(int argc, char **argv)
 	check_delete();
 	check_sigev_none(CLOCK_MONOTONIC, "CLOCK_MONOTONIC");
 	check_sigev_none(CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID");
+	check_gettime(CLOCK_MONOTONIC, "CLOCK_MONOTONIC");
+	check_gettime(CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID");
+	check_gettime(CLOCK_THREAD_CPUTIME_ID, "CLOCK_THREAD_CPUTIME_ID");
 
 	ksft_finished();
 }