kselftests: timers: set-timer-lat: Add one-shot timer test cases

These testcases are motivated by a recent alarmtimer regression, which
caused one-shot CLOCK_{BOOTTIME,REALTIME}_ALARM timers to become
periodic timers.

The new testcases are very similar to the existing testcases for
repeating timers.  But rather than waiting for 5 alarms, they wait for 5
seconds and verify that the alarm fired exactly once.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Stephen Boyd <stephen.boyd@linaro.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

tools/testing/selftests/timers/set-timer-lat.c

@@ -20,6 +20,7 @@
  */
 
 
+#include <errno.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <time.h>
@@ -122,17 +123,17 @@ void sigalarm(int signo)
 		max_latency_ns = delta_ns;
 }
 
-void describe_timer(int flags)
+void describe_timer(int flags, int interval)
 {
-	printf("%-22s %s ",
+	printf("%-22s %s %s ",
 			clockstring(clock_id),
-			flags ? "ABSTIME":"RELTIME");
+			flags ? "ABSTIME":"RELTIME",
+			interval ? "PERIODIC":"ONE-SHOT");
 }
 
-int do_timer(int clock_id, int flags)
+int setup_timer(int clock_id, int flags, int interval, timer_t *tm1)
 {
 	struct sigevent se;
-	timer_t tm1;
 	struct itimerspec its1, its2;
 	int err;
 
@@ -146,7 +147,7 @@ int do_timer(int clock_id, int flags)
 	alarmcount = 0;
 	timer_fired_early = 0;
 
-	err = timer_create(clock_id, &se, &tm1);
+	err = timer_create(clock_id, &se, tm1);
 	if (err) {
 		if ((clock_id == CLOCK_REALTIME_ALARM) ||
 		    (clock_id == CLOCK_BOOTTIME_ALARM)) {
@@ -167,19 +168,23 @@ int do_timer(int clock_id, int flags)
 		its1.it_value.tv_sec = TIMER_SECS;
 		its1.it_value.tv_nsec = 0;
 	}
-	its1.it_interval.tv_sec = TIMER_SECS;
+	its1.it_interval.tv_sec = interval;
 	its1.it_interval.tv_nsec = 0;
 
-	err = timer_settime(tm1, flags, &its1, &its2);
+	err = timer_settime(*tm1, flags, &its1, &its2);
 	if (err) {
 		printf("%s - timer_settime() failed\n", clockstring(clock_id));
 		return -1;
 	}
 
-	while (alarmcount < 5)
-		sleep(1);
+	return 0;
+}
+
+int check_timer_latency(int flags, int interval)
+{
+	int err = 0;
 
-	describe_timer(flags);
+	describe_timer(flags, interval);
 	printf("timer fired early: %7d : ", timer_fired_early);
 	if (!timer_fired_early) {
 		printf("[OK]\n");
@@ -188,10 +193,9 @@ int do_timer(int clock_id, int flags)
 		err = -1;
 	}
 
-	describe_timer(flags);
+	describe_timer(flags, interval);
 	printf("max latency: %10lld ns : ", max_latency_ns);
 
-	timer_delete(tm1);
 	if (max_latency_ns < UNRESONABLE_LATENCY) {
 		printf("[OK]\n");
 	} else {
@@ -201,6 +205,60 @@ int do_timer(int clock_id, int flags)
 	return err;
 }
 
+int check_alarmcount(int flags, int interval)
+{
+	describe_timer(flags, interval);
+	printf("count: %19d : ", alarmcount);
+	if (alarmcount == 1) {
+		printf("[OK]\n");
+		return 0;
+	}
+	printf("[FAILED]\n");
+	return -1;
+}
+
+int do_timer(int clock_id, int flags)
+{
+	timer_t tm1;
+	const int interval = TIMER_SECS;
+	int err;
+
+	err = setup_timer(clock_id, flags, interval, &tm1);
+	if (err)
+		return err;
+
+	while (alarmcount < 5)
+		sleep(1);
+
+	timer_delete(tm1);
+	return check_timer_latency(flags, interval);
+}
+
+int do_timer_oneshot(int clock_id, int flags)
+{
+	timer_t tm1;
+	const int interval = 0;
+	struct timeval timeout;
+	fd_set fds;
+	int err;
+
+	err = setup_timer(clock_id, flags, interval, &tm1);
+	if (err)
+		return err;
+
+	memset(&timeout, 0, sizeof(timeout));
+	timeout.tv_sec = 5;
+	FD_ZERO(&fds);
+	do {
+		err = select(FD_SETSIZE, &fds, NULL, NULL, &timeout);
+	} while (err == -1 && errno == EINTR);
+
+	timer_delete(tm1);
+	err = check_timer_latency(flags, interval);
+	err |= check_alarmcount(flags, interval);
+	return err;
+}
+
 int main(void)
 {
 	struct sigaction act;
@@ -226,6 +284,8 @@ int main(void)
 
 		ret |= do_timer(clock_id, TIMER_ABSTIME);
 		ret |= do_timer(clock_id, 0);
+		ret |= do_timer_oneshot(clock_id, TIMER_ABSTIME);
+		ret |= do_timer_oneshot(clock_id, 0);
 	}
 	if (ret)
 		return ksft_exit_fail();