Re: [PATCH 3/7] ntdll: Use CLOCK_REALTIME_COARSE for NtQuerySystemTime() if it has sufficient resolution.

[Huw Davies]

On Thu, May 02, 2019 at 08:47:29AM -0500, Ken Thomases wrote:
> On May 2, 2019, at 3:45 AM, Huw Davies  wrote:
> > -NTSTATUS WINAPI NtQuerySystemTime( PLARGE_INTEGER Time )
> > +NTSTATUS WINAPI NtQuerySystemTime( LARGE_INTEGER *time )
> > {
> > - struct timeval now;
> >
> > +#if defined(HAVE_CLOCK_GETTIME)
> > - struct timespec ts;
> > - static clockid_t clock_id = -1;
> > - gettimeofday( &now, 0 );
> > - Time->QuadPart = now.tv_sec * (ULONGLONG)TICKSPERSEC + TICKS_1601_TO_1970;
> > - Time->QuadPart += now.tv_usec * 10;
> > - if (clock_id == -1)
> > - {
> > -
> >    struct timespec res;
> > -
> > -
> >    /* Use CLOCK_REALTIME_COARSE if it has 1 ms or better resolution */
> > -
> >    if (!clock_getres( CLOCK_REALTIME_COARSE, &res ) && res.tv_sec == 0 && res.tv_nsec <= 1000000)
> > -
> >        clock_id = CLOCK_REALTIME_COARSE;
> > -
> >    else
> > -
> >        clock_id = CLOCK_REALTIME;
>
> Having clock_gettime() doesn't necessarily imply having
> CLOCK_REALTIME_COARSE.  It seems that baseline POSIX only requires
> CLOCK_REALTIME.

Good point, thanks!

Huw.