Re: __profile_frequency

[George Anzinger <george at mvista dot com>]

Richard Henderson wrote:
> Um, so how's 
>
> 45        tim.it_interval.tv_sec = 0;
> 46        tim.it_interval.tv_usec = 1;
> 47        tim.it_value.tv_sec = 0;
> 48        tim.it_value.tv_usec = 0;
> 49        __setitimer(ITIMER_REAL, &tim, 0);
> 50        __setitimer(ITIMER_REAL, 0, &tim);
> 51        if (tim.it_interval.tv_usec < 2)
> 52          return 0;
> 53        return (1000000 / tim.it_interval.tv_usec);
>
> supposed to work?  AFAICS there's no reason for the kernel 
> (1) not to round down instead of up and (2) not do something
> else legal like schedule in between the two __setitimer calls.

Time is ALWAYS rounded UP as required by the standard.  2 is legal, however.

-g
> On alpha-linux 2.5.73, tim is always zero after the second
> call, which results in divide-by-zero FPE in __sprofil.
>
> Why wouldn't this be the same as __getclktck?
>
>
> r~

--
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