[2/3] lib: implement rtctime_save and rtctime_restore function

From: Cixi Geng <cixi.geng1@unisoc.com>

* Reading the RTC in the setup as well as timestamping with monotonic
  timer
* Getting a second monotonic timestamp in the cleanup
* Setting the RTC to the value taken in setup plus the difference in
  the monotonic timer timestamps

Signed-off-by: Cixi Geng <cixi.geng1@unisoc.com>
---
 include/tst_wallclock.h |  4 ++++
 lib/tst_wallclock.c     | 42 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

>  static struct timespec real_begin, mono_begin;
>  
> +static struct rtc_time rtc_begin;
> +
>  static int clock_saved;
>  
>  void tst_wallclock_save(void)
> @@ -58,3 +61,42 @@ void tst_wallclock_restore(void)
>  	if (tst_clock_settime(CLOCK_REALTIME, &adjust))
>  		tst_brk(TBROK | TERRNO, "tst_clock_settime() realtime failed");
>  }
> +
> +void tst_rtctime_save(void)
> +{
> +	/* save initial monotonic time to restore it when needed */
> +	if (tst_rtc_gettime(&rtc_begin))
> +		tst_brk(TBROK | TERRNO, "tst_rtc_gettime() realtime failed");
> +
> +	if (tst_clock_gettime(CLOCK_MONOTONIC_RAW, &mono_begin))
> +		tst_brk(TBROK | TERRNO, "tst_clock_gettime() monotonic failed");
> +
> +	clock_saved = 1;

It would be better if we defined rtc_clock_saved for the rtc* functions
instead.

> +}
> +
> +void tst_rtctime_restore(void)
> +{
> +	static struct timespec mono_end, elapsed;
> +	static struct timespec rtc_begin_tm, rtc_adjust;
> +	static struct rtc_time rtc_restore;
> +
> +	if (!clock_saved)
> +		return;
> +
> +	clock_saved = 0;
> +
> +	if (tst_clock_gettime(CLOCK_MONOTONIC_RAW, &mono_end))
> +		tst_brk(TBROK | TERRNO, "tst_clock_gettime() monotonic failed");
> +
> +	elapsed = tst_timespec_diff(mono_end, mono_begin);
> +
> +	rtc_begin_tm.tv_sec = tst_rtc_tm_to_time(&rtc_begin);

We should clear the tv_nsec here otherwise it will contain garbage.

> +	rtc_adjust = tst_timespec_add(rtc_begin_tm, elapsed);
> +
> +	tst_rtc_time_to_tm(rtc_adjust.tv_sec, &rtc_restore);
> +
> +	/* restore realtime clock based on monotonic delta */
> +	if (tst_rtc_settime(&rtc_restore))
> +		tst_brk(TBROK | TERRNO, "tst_rtc_settime() realtime failed");
> +}

Other than this, it looks good.

Cyril Hrubis <chrubis@suse.cz> 于2021年1月7日周四 下午9:56写道：
>
> >  static struct timespec real_begin, mono_begin;
> >
> > +static struct rtc_time rtc_begin;
> > +
> >  static int clock_saved;
> >
> >  void tst_wallclock_save(void)
> > @@ -58,3 +61,42 @@ void tst_wallclock_restore(void)
> >       if (tst_clock_settime(CLOCK_REALTIME, &adjust))
> >               tst_brk(TBROK | TERRNO, "tst_clock_settime() realtime failed");
> >  }
> > +
> > +void tst_rtctime_save(void)
> > +{
> > +     /* save initial monotonic time to restore it when needed */
> > +     if (tst_rtc_gettime(&rtc_begin))
> > +             tst_brk(TBROK | TERRNO, "tst_rtc_gettime() realtime failed");
> > +
> > +     if (tst_clock_gettime(CLOCK_MONOTONIC_RAW, &mono_begin))
> > +             tst_brk(TBROK | TERRNO, "tst_clock_gettime() monotonic failed");
> > +
> > +     clock_saved = 1;
>
> It would be better if we defined rtc_clock_saved for the rtc* functions
> instead.
>
> > +}
> > +
> > +void tst_rtctime_restore(void)
> > +{
> > +     static struct timespec mono_end, elapsed;
> > +     static struct timespec rtc_begin_tm, rtc_adjust;
> > +     static struct rtc_time rtc_restore;
> > +
> > +     if (!clock_saved)
> > +             return;
> > +
> > +     clock_saved = 0;
> > +
> > +     if (tst_clock_gettime(CLOCK_MONOTONIC_RAW, &mono_end))
> > +             tst_brk(TBROK | TERRNO, "tst_clock_gettime() monotonic failed");
> > +
> > +     elapsed = tst_timespec_diff(mono_end, mono_begin);
> > +
> > +     rtc_begin_tm.tv_sec = tst_rtc_tm_to_time(&rtc_begin);
>
> We should clear the tv_nsec here otherwise it will contain garbage.
The rtc_begin_tm is defined in this function， and tv_nsec never assigned，
so I think it will not produce any garbage.
>
> > +     rtc_adjust = tst_timespec_add(rtc_begin_tm, elapsed);
> > +
> > +     tst_rtc_time_to_tm(rtc_adjust.tv_sec, &rtc_restore);
> > +
> > +     /* restore realtime clock based on monotonic delta */
> > +     if (tst_rtc_settime(&rtc_restore))
> > +             tst_brk(TBROK | TERRNO, "tst_rtc_settime() realtime failed");
> > +}
>
> Other than this, it looks good.
>
> --
> Cyril Hrubis
> chrubis@suse.cz

Hi!
> > > +void tst_rtctime_restore(void)
> > > +{
> > > +     static struct timespec mono_end, elapsed;
> > > +     static struct timespec rtc_begin_tm, rtc_adjust;
> > > +     static struct rtc_time rtc_restore;
> > > +
> > > +     if (!clock_saved)
> > > +             return;
> > > +
> > > +     clock_saved = 0;
> > > +
> > > +     if (tst_clock_gettime(CLOCK_MONOTONIC_RAW, &mono_end))
> > > +             tst_brk(TBROK | TERRNO, "tst_clock_gettime() monotonic failed");
> > > +
> > > +     elapsed = tst_timespec_diff(mono_end, mono_begin);
> > > +
> > > +     rtc_begin_tm.tv_sec = tst_rtc_tm_to_time(&rtc_begin);
> >
> > We should clear the tv_nsec here otherwise it will contain garbage.
> The rtc_begin_tm is defined in this function??? and tv_nsec never assigned???
> so I think it will not produce any garbage.

It's never assigned and declared on stack, so it will contain garbage
which will be eventually added to the rtc_adjust.tv_sec. Technically
the tv_nsec is long, so on 64 bit platform it may add up to 10^10
seconds to the result if we are unlucky and upper bits are set. On 32
bit there is not much room for error btw, up to 2 seconds since long is
only 4bytes there.

> > > +     rtc_adjust = tst_timespec_add(rtc_begin_tm, elapsed);
> > > +
> > > +     tst_rtc_time_to_tm(rtc_adjust.tv_sec, &rtc_restore);
> > > +
> > > +     /* restore realtime clock based on monotonic delta */
> > > +     if (tst_rtc_settime(&rtc_restore))
> > > +             tst_brk(TBROK | TERRNO, "tst_rtc_settime() realtime failed");
> > > +}
> >
> > Other than this, it looks good.
> >
> > --
> > Cyril Hrubis
> > chrubis@suse.cz

Cyril Hrubis <chrubis@suse.cz> 于2021年1月8日周五 下午5:33写道：
>
> Hi!
> > > > +void tst_rtctime_restore(void)
> > > > +{
> > > > +     static struct timespec mono_end, elapsed;
> > > > +     static struct timespec rtc_begin_tm, rtc_adjust;
> > > > +     static struct rtc_time rtc_restore;
> > > > +
> > > > +     if (!clock_saved)
> > > > +             return;
> > > > +
> > > > +     clock_saved = 0;
> > > > +
> > > > +     if (tst_clock_gettime(CLOCK_MONOTONIC_RAW, &mono_end))
> > > > +             tst_brk(TBROK | TERRNO, "tst_clock_gettime() monotonic failed");
> > > > +
> > > > +     elapsed = tst_timespec_diff(mono_end, mono_begin);
> > > > +
> > > > +     rtc_begin_tm.tv_sec = tst_rtc_tm_to_time(&rtc_begin);
> > >
> > > We should clear the tv_nsec here otherwise it will contain garbage.
> > The rtc_begin_tm is defined in this function??? and tv_nsec never assigned???
> > so I think it will not produce any garbage.
>
> It's never assigned and declared on stack, so it will contain garbage
> which will be eventually added to the rtc_adjust.tv_sec. Technically
> the tv_nsec is long, so on 64 bit platform it may add up to 10^10
> seconds to the result if we are unlucky and upper bits are set. On 32
> bit there is not much room for error btw, up to 2 seconds since long is
> only 4bytes there.
>

ok,I got it, thanks for you explain, I will fixed this issue

> > > > +     rtc_adjust = tst_timespec_add(rtc_begin_tm, elapsed);
> > > > +
> > > > +     tst_rtc_time_to_tm(rtc_adjust.tv_sec, &rtc_restore);
> > > > +
> > > > +     /* restore realtime clock based on monotonic delta */
> > > > +     if (tst_rtc_settime(&rtc_restore))
> > > > +             tst_brk(TBROK | TERRNO, "tst_rtc_settime() realtime failed");
> > > > +}
> > >
> > > Other than this, it looks good.
> > >
> > > --
> > > Cyril Hrubis
> > > chrubis@suse.cz
>
> --
> Cyril Hrubis
> chrubis@suse.cz