Re: POSIX timer syscalls

[george anzinger <george@mvista.com>]

Eric Piel wrote:
> george anzinger wrote:
> 
>>By the way, I am seeing some reports from the clock_nanosleep test
>>about sleeping too long or too short.  The too long appears to be just
>>not being able to preempt what ever else is running.  The too short
>>(on the x86) is, I believe, due to the fact that more that 1/HZ is
>>clocked on the wall clock each jiffie.
>>
>>Try this:
>>
>>time sleep 60
>>
>>On the x86 it reports less than 60, NOT good.
>>
> 
> I've run the test programs and they pass everything well (with my
> patchs) excepted the nanosleeps which seems to be finnished a bit too
> early. My system test is a 2.5.64 patched on a 4xItaniumII.
> 
> My main question is to know if it's a problem even if the difference
> between the wakeup time and the requested time is smaller than the
> resolution of the clock, 976562ns ? I mean, at the resolution of the
> clock we could consider we woke up right at the good time, couldn't we?
> 
> In addition time sleep 60 always gave me time over 1 minute, I guess
> it's a good point. 
> 
> Here is a part of the log of 'do_test':
> 
> Testing behavor with clock seting...
> Retarding the clock
> Clock did not seem to move
>  was:           1046969027s 703359000ns
>  requested:     1046969023s 703359000ns
>  now:           1046969022s 467072000ns
>  diff is -1.236286998sec
> Cool clock_nanosleeptest.c,379:clock_nanosleep(clock, TIMER_ABSTIME,
> &ts, NULL)

Is it possible that a "clock_was_set()" call was missed?  I.e in the 
set_timeofday code?
> 
> Testing signal behavor...
> handler1 entered: signal 31
> expected clock_nanosleeptest.c,227:clock_nanosleep(clock, 0, &ts, &rs):
> Interrupted system call
> Time remaining is 0s 989257306ns
> clock_nanosleeptest.c,245:slept too short!
>  requested:     275s 207032000ns
>  now:           275s 207030632ns
>  diff is -0.000001368sec
> 
> Testing undelivered signal behavor...
> Cool clock_nanosleeptest.c,267:clock_nanosleep(clock, 0, &ts, &rs)
> clock_nanosleeptest.c,283:slept too short!
>  requested:     275s 223633000ns
>  now:           275s 223632698ns
>  diff is -0.000000302sec
> 
> 
>  --Eric
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-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml