linux-kernel - [PATCH] selftests: timers: set-timer-lat: Fix hang when testing unsupported alarms

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Date:   Thu, 21 Sep 2017 13:45:10 -0600
From:   Shuah Khan <shuahkh@....samsung.com>
To:     john.stultz@...aro.org, tglx@...utronix.de, sboyd@...eaurora.org,
        ghackmann@...gle.com, shuah@...nel.org
Cc:     Shuah Khan <shuahkh@....samsung.com>, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: [PATCH] selftests: timers: set-timer-lat: Fix hang when testing unsupported alarms

When timer_create() fails on a bootime or realtime clock, setup_timer()
returns 0 as if timer has been set. Callers wait forever for the timer
to expire.

This hang is seen on a system that doesn't have support for:

CLOCK_REALTIME_ALARM   ABSTIME missing CAP_WAKE_ALARM? : [UNSUPPORTED]

Test hangs waiting for a timer that hasn't been set to expire.

Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
---
 tools/testing/selftests/timers/set-timer-lat.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/timers/set-timer-lat.c b/tools/testing/selftests/timers/set-timer-lat.c
index 9c92b7bd5641..ab2fe225e051 100644
--- a/tools/testing/selftests/timers/set-timer-lat.c
+++ b/tools/testing/selftests/timers/set-timer-lat.c
@@ -143,7 +143,8 @@ int setup_timer(int clock_id, int flags, int interval, timer_t *tm1)
 			printf("%-22s %s missing CAP_WAKE_ALARM?    : [UNSUPPORTED]\n",
 					clockstring(clock_id),
 					flags ? "ABSTIME":"RELTIME");
-			return 0;
+			/* Indicate timer isn't set, so caller doesn't wait */
+			return 1;
 		}
 		printf("%s - timer_create() failed\n", clockstring(clock_id));
 		return -1;
-- 
2.11.0