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

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

[Shuah Khan]

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@osg.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

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

[Shuah Khan]

Hi John/Greg,

On 09/21/2017 01:45 PM, Shuah Khan wrote:
> 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@osg.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;
> 

I assume you are good with this fix. I plan to apply it to linux-kselftest fixes
today. Please let me know if you have any objections.

thanks,
-- Shuah

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

[Greg Hackmann]

On 09/22/2017 07:41 AM, Shuah Khan wrote:
> I assume you are good with this fix. I plan to apply it to linux-kselftest fixes
> today. Please let me know if you have any objections.
> 
> thanks,
> -- Shuah
> 

AIUI this check was added so set-timer-lat would treat a missing 
CAP_WAKE_ALARM as a skipped test (rather than making the entire test 
fail).  So setup_timer()'s callers would need to treat this as a special 
case, by returning immediately but with a return value of 0.

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

[Shuah Khan]

On 09/22/2017 09:51 AM, Greg Hackmann wrote:
> On 09/22/2017 07:41 AM, Shuah Khan wrote:
>> I assume you are good with this fix. I plan to apply it to linux-kselftest fixes
>> today. Please let me know if you have any objections.
>>
>> thanks,
>> -- Shuah
>>
> 
> AIUI this check was added so set-timer-lat would treat a missing CAP_WAKE_ALARM as a skipped test (rather than making the entire test fail).  So setup_timer()'s callers would need to treat this as a special case, by returning immediately but with a return value of 0.

I see. Instead of marking the UNSUPPORTED case as fail, you would like
to see it as skip.

The following is the output with this patch. So I think you don't want to
see the "Bail out!" at the end.

I will make the change and send v2.

./set-timer-lat 
Setting timers for every 1 seconds
CLOCK_REALTIME         ABSTIME PERIODIC timer fired early:       0 : [OK]
CLOCK_REALTIME         ABSTIME PERIODIC max latency:     479361 ns : [OK]
CLOCK_REALTIME         RELTIME PERIODIC timer fired early:       0 : [OK]
CLOCK_REALTIME         RELTIME PERIODIC max latency:     210625 ns : [OK]
CLOCK_REALTIME         ABSTIME ONE-SHOT timer fired early:       0 : [OK]
CLOCK_REALTIME         ABSTIME ONE-SHOT max latency:     152892 ns : [OK]
CLOCK_REALTIME         ABSTIME ONE-SHOT count:                   1 : [OK]
CLOCK_REALTIME         RELTIME ONE-SHOT timer fired early:       0 : [OK]
CLOCK_REALTIME         RELTIME ONE-SHOT max latency:     167839 ns : [OK]
CLOCK_REALTIME         RELTIME ONE-SHOT count:                   1 : [OK]
CLOCK_MONOTONIC        ABSTIME PERIODIC timer fired early:       0 : [OK]
CLOCK_MONOTONIC        ABSTIME PERIODIC max latency:     190204 ns : [OK]
CLOCK_MONOTONIC        RELTIME PERIODIC timer fired early:       0 : [OK]
CLOCK_MONOTONIC        RELTIME PERIODIC max latency:     212418 ns : [OK]
CLOCK_MONOTONIC        ABSTIME ONE-SHOT timer fired early:       0 : [OK]
CLOCK_MONOTONIC        ABSTIME ONE-SHOT max latency:     158816 ns : [OK]
CLOCK_MONOTONIC        ABSTIME ONE-SHOT count:                   1 : [OK]
CLOCK_MONOTONIC        RELTIME ONE-SHOT timer fired early:       0 : [OK]
CLOCK_MONOTONIC        RELTIME ONE-SHOT max latency:     172362 ns : [OK]
CLOCK_MONOTONIC        RELTIME ONE-SHOT count:                   1 : [OK]
CLOCK_BOOTTIME         ABSTIME PERIODIC timer fired early:       0 : [OK]
CLOCK_BOOTTIME         ABSTIME PERIODIC max latency:     180767 ns : [OK]
CLOCK_BOOTTIME         RELTIME PERIODIC timer fired early:       0 : [OK]
CLOCK_BOOTTIME         RELTIME PERIODIC max latency:     202772 ns : [OK]
CLOCK_BOOTTIME         ABSTIME ONE-SHOT timer fired early:       0 : [OK]
CLOCK_BOOTTIME         ABSTIME ONE-SHOT max latency:     117733 ns : [OK]
CLOCK_BOOTTIME         ABSTIME ONE-SHOT count:                   1 : [OK]
CLOCK_BOOTTIME         RELTIME ONE-SHOT timer fired early:       0 : [OK]
CLOCK_BOOTTIME         RELTIME ONE-SHOT max latency:     171882 ns : [OK]
CLOCK_BOOTTIME         RELTIME ONE-SHOT count:                   1 : [OK]
CLOCK_REALTIME_ALARM   ABSTIME missing CAP_WAKE_ALARM?    : [UNSUPPORTED]
CLOCK_REALTIME_ALARM   RELTIME missing CAP_WAKE_ALARM?    : [UNSUPPORTED]
CLOCK_REALTIME_ALARM   ABSTIME missing CAP_WAKE_ALARM?    : [UNSUPPORTED]
CLOCK_REALTIME_ALARM   RELTIME missing CAP_WAKE_ALARM?    : [UNSUPPORTED]
CLOCK_BOOTTIME_ALARM   ABSTIME missing CAP_WAKE_ALARM?    : [UNSUPPORTED]
CLOCK_BOOTTIME_ALARM   RELTIME missing CAP_WAKE_ALARM?    : [UNSUPPORTED]
CLOCK_BOOTTIME_ALARM   ABSTIME missing CAP_WAKE_ALARM?    : [UNSUPPORTED]
CLOCK_BOOTTIME_ALARM   RELTIME missing CAP_WAKE_ALARM?    : [UNSUPPORTED]
CLOCK_TAI              ABSTIME PERIODIC timer fired early:       0 : [OK]
CLOCK_TAI              ABSTIME PERIODIC max latency:     183220 ns : [OK]
CLOCK_TAI              RELTIME PERIODIC timer fired early:       0 : [OK]
CLOCK_TAI              RELTIME PERIODIC max latency:     201380 ns : [OK]
CLOCK_TAI              ABSTIME ONE-SHOT timer fired early:       0 : [OK]
CLOCK_TAI              ABSTIME ONE-SHOT max latency:     117230 ns : [OK]
CLOCK_TAI              ABSTIME ONE-SHOT count:                   1 : [OK]
CLOCK_TAI              RELTIME ONE-SHOT timer fired early:       0 : [OK]
CLOCK_TAI              RELTIME ONE-SHOT max latency:     154236 ns : [OK]
CLOCK_TAI              RELTIME ONE-SHOT count:                   1 : [OK]
Bail out!
Pass 0 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..0


thanks,
-- Shuah