[LTP] [PATCH] syscalls/timer_settime01: adjust for rounding from nsec to usec

[LTP] [PATCH] syscalls/timer_settime01: adjust for rounding from nsec to usec

[Thadeu Lima de Souza Cascardo]

When using TIMER_ABSTIME, the value is added to the current clock time.
However, usecs is used instead of nsecs, leading to a possible rounding up from
tst_ts_to_us.

That rounding can lead to up to 500 nsecs of difference between the current
time and the absolute time used for setting the timer. When reading the timer
back, that same difference can be found, which leads to a test failure.

Accounting for that possible difference in the time allows the test to pass.

This can be easily reproducible by booting linux with clocksource=jiffies.

Fixes: b34e243e85dd (syscalls/timer_settime01: Make sure the timer fires)
Reported-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
---
 testcases/kernel/syscalls/timer_settime/timer_settime01.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/testcases/kernel/syscalls/timer_settime/timer_settime01.c b/testcases/kernel/syscalls/timer_settime/timer_settime01.c
index 67143e8f88b2..7ecf0c18d1c4 100644
--- a/testcases/kernel/syscalls/timer_settime/timer_settime01.c
+++ b/testcases/kernel/syscalls/timer_settime/timer_settime01.c
@@ -149,10 +149,15 @@ static void run(unsigned int n)
 		if (TST_RET != 0) {
 			tst_res(TFAIL | TTERRNO, "timer_gettime(%s) failed",
 				get_clock_str(clock));
+		/*
+		 * With TIMER_ABSTIME, we add to the current clock after
+		 * rounding up by 500 ns to the value. Do the same here after
+		 * reading the timer back.
+		 */
 		} else if ((tst_its_get_interval_nsec(new_set) !=
 				tc->it_interval_tv_usec * 1000) ||
 			   (tst_its_get_value_nsec(new_set) >
-				MAX(tc->it_value_tv_usec * 1000, tc->it_interval_tv_usec * 1000))) {
+				MAX(tc->it_value_tv_usec * 1000 + 500, tc->it_interval_tv_usec * 1000))) {
 			tst_res(TFAIL | TTERRNO,
 				"timer_gettime(%s) reported bad values (%llu: %llu)",
 				get_clock_str(clock),
-- 
2.25.1

[LTP] [PATCH] syscalls/timer_settime01: adjust for rounding from nsec to usec

[Cyril Hrubis]

Hi!
What about this change instead?

diff --git a/testcases/kernel/syscalls/timer_settime/timer_settime01.c b/testcases/kernel/syscalls/timer_settime/timer_settime01.c
index 67143e8f8..599ef2891 100644
--- a/testcases/kernel/syscalls/timer_settime/timer_settime01.c
+++ b/testcases/kernel/syscalls/timer_settime/timer_settime01.c
@@ -132,11 +132,13 @@ static void run(unsigned int n)
 					get_clock_str(clock));
 				continue;
 			}
-			val += tst_ts_to_us(timenow);
+			tst_ts_add_us(timenow, val);
+			tst_its_set_value_from_ts(&new_set, timenow);
+		} else {
+			tst_its_set_value_from_us(&new_set, val);
 		}
 
 		tst_its_set_interval_from_us(&new_set, tc->it_interval_tv_usec);
-		tst_its_set_value_from_us(&new_set, val);
 
 		TEST(tv->timer_settime(timer, tc->flag, tst_its_get(&new_set), tst_its_get(tc->old_ptr)));
 


By adding the us to the timenow first and then setting the its.value
from it we can avoid the rounding completely.

-- 
Cyril Hrubis
chrubis@suse.cz

[LTP] [PATCH] syscalls/timer_settime01: adjust for rounding from nsec to usec

[Cyril Hrubis]

Hi!
> What about this change instead?
> 
> diff --git a/testcases/kernel/syscalls/timer_settime/timer_settime01.c b/testcases/kernel/syscalls/timer_settime/timer_settime01.c
> index 67143e8f8..599ef2891 100644
> --- a/testcases/kernel/syscalls/timer_settime/timer_settime01.c
> +++ b/testcases/kernel/syscalls/timer_settime/timer_settime01.c
> @@ -132,11 +132,13 @@ static void run(unsigned int n)
>  					get_clock_str(clock));
>  				continue;
>  			}
> -			val += tst_ts_to_us(timenow);
> +			tst_ts_add_us(timenow, val);
> +			tst_its_set_value_from_ts(&new_set, timenow);
> +		} else {
> +			tst_its_set_value_from_us(&new_set, val);
>  		}
>  
>  		tst_its_set_interval_from_us(&new_set, tc->it_interval_tv_usec);
> -		tst_its_set_value_from_us(&new_set, val);
>  
>  		TEST(tv->timer_settime(timer, tc->flag, tst_its_get(&new_set), tst_its_get(tc->old_ptr)));
>  
> 
> 
> By adding the us to the timenow first and then setting the its.value
> from it we can avoid the rounding completely.

Does this fix work for you?

-- 
Cyril Hrubis
chrubis@suse.cz

[LTP] syscalls/timer_settime01: adjust for rounding from nsec to usec

[Alexander Egorenkov]

Hi all,

the patch from Chris fixes the below issue on s390x:

timer_settime01.c:96: TINFO: Testing for using absolute time:
timer_settime01.c:169: TPASS: timer_settime(CLOCK_REALTIME) passed
timer_settime01.c:169: TPASS: timer_settime(CLOCK_MONOTONIC) passed
timer_settime01.c:169: TPASS: timer_settime(CLOCK_PROCESS_CPUTIME_ID) passed
timer_settime01.c:169: TPASS: timer_settime(CLOCK_THREAD_CPUTIME_ID) passed
timer_settime01.c:169: TPASS: timer_settime(CLOCK_BOOTTIME) passed
timer_settime01.c:111: TCONF: CLOCK_BOOTTIME_ALARM unsupported: EOPNOTSUPP (95)
timer_settime01.c:111: TCONF: CLOCK_REALTIME_ALARM unsupported: EOPNOTSUPP (95)
timer_settime01.c:156: TFAIL: timer_gettime(CLOCK_TAI) reported bad values (0: 50000019): SUCCESS (0)
timer_settime01.c:169: TPASS: timer_settime(CLOCK_TAI) passed

and

timer_settime01.c:96: TINFO: Testing for using absolute time:
timer_settime01.c:169: TPASS: timer_settime(CLOCK_REALTIME) passed
timer_settime01.c:169: TPASS: timer_settime(CLOCK_MONOTONIC) passed
timer_settime01.c:169: TPASS: timer_settime(CLOCK_PROCESS_CPUTIME_ID) passed
timer_settime01.c:169: TPASS: timer_settime(CLOCK_THREAD_CPUTIME_ID) passed
timer_settime01.c:156: TFAIL: timer_gettime(CLOCK_BOOTTIME) reported bad values (0: 50000097): SUCCESS (0)
timer_settime01.c:169: TPASS: timer_settime(CLOCK_BOOTTIME) passed
timer_settime01.c:111: TCONF: CLOCK_BOOTTIME_ALARM unsupported: EOPNOTSUPP (95)
timer_settime01.c:111: TCONF: CLOCK_REALTIME_ALARM unsupported: EOPNOTSUPP (95)
timer_settime01.c:169: TPASS: timer_settime(CLOCK_TAI) passed



Regards
Alex

[LTP] syscalls/timer_settime01: adjust for rounding from nsec to usec

[Cyril Hrubis]

Hi!
> the patch from Chris fixes the below issue on s390x:

And what about the simpler solution I've proposed in the reply, does
that one work fine as well?

-- 
Cyril Hrubis
chrubis@suse.cz

[LTP] syscalls/timer_settime01: adjust for rounding from nsec to usec

[Alexander Egorenkov]

Cyril Hrubis <chrubis@suse.cz> writes:

> Hi!
>> the patch from Chris fixes the below issue on s390x:
>
> And what about the simpler solution I've proposed in the reply, does
> that one work fine as well?

Hi Cyril,

first, sorry for butchering your name :/

Second, I tested now both patches on a heavy loaded system (with
stress-ng) and both seem to solve my issues. I ran a test 1000 times
(-i 1000) and couldn't reproduce it anymore.

Regards
Alex

[LTP] [PATCH] syscalls/timer_settime01: adjust for rounding from nsec to usec

[Thadeu Lima de Souza Cascardo]

On Tue, Oct 20, 2020 at 02:23:51PM +0200, Cyril Hrubis wrote:
> Hi!
> > What about this change instead?
> > 
> > diff --git a/testcases/kernel/syscalls/timer_settime/timer_settime01.c b/testcases/kernel/syscalls/timer_settime/timer_settime01.c
> > index 67143e8f8..599ef2891 100644
> > --- a/testcases/kernel/syscalls/timer_settime/timer_settime01.c
> > +++ b/testcases/kernel/syscalls/timer_settime/timer_settime01.c
> > @@ -132,11 +132,13 @@ static void run(unsigned int n)
> >  					get_clock_str(clock));
> >  				continue;
> >  			}
> > -			val += tst_ts_to_us(timenow);
> > +			tst_ts_add_us(timenow, val);
> > +			tst_its_set_value_from_ts(&new_set, timenow);
> > +		} else {
> > +			tst_its_set_value_from_us(&new_set, val);
> >  		}
> >  
> >  		tst_its_set_interval_from_us(&new_set, tc->it_interval_tv_usec);
> > -		tst_its_set_value_from_us(&new_set, val);
> >  
> >  		TEST(tv->timer_settime(timer, tc->flag, tst_its_get(&new_set), tst_its_get(tc->old_ptr)));
> >  
> > 
> > 
> > By adding the us to the timenow first and then setting the its.value
> > from it we can avoid the rounding completely.
> 
> Does this fix work for you?
> 

Sorry, I was out on vacation. This fixes it for me when using
clocksource=jiffies.

Thanks.
Cascardo.

> -- 
> Cyril Hrubis
> chrubis@suse.cz

[LTP] [PATCH] syscalls/timer_settime01: adjust for rounding from nsec to usec

[Cyril Hrubis]

Hi!
> Sorry, I was out on vacation. This fixes it for me when using
> clocksource=jiffies.

Thanks a lot for testing, pushed.

-- 
Cyril Hrubis
chrubis@suse.cz