[PATCH] dm: rtc: Avoid a race in the rtc_reset test

[Simon Glass]

Hi Heinrich,

On Mon, 1 Aug 2022 at 02:11, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 7/31/22 20:27, Simon Glass wrote:
> > Since resetting the RTC on sandbox causes it to read the base time from
> > the system, we cannot rely on this being unchanged since it was last read.
> > Allow for a one-second delay.
> >
> > Fixes: https://source.denx.de/u-boot/u-boot/-/issues/4
> > Reported-by: Bin Meng <bmeng.cn at gmail.com>
> > Reported-by: Tom Rini <trini at konsulko.com>
> > Suggested-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
> > Signed-off-by: Simon Glass <sjg at chromium.org>
> > ---
> >
> >   test/dm/rtc.c | 11 ++++++++---
> >   1 file changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/test/dm/rtc.c b/test/dm/rtc.c
> > index c7f9f8f0ce7..403bf5c640a 100644
> > --- a/test/dm/rtc.c
> > +++ b/test/dm/rtc.c
> > @@ -245,16 +245,21 @@ static int dm_test_rtc_reset(struct unit_test_state *uts)
> >       ut_assertok(dm_rtc_get(dev, &now));
> >
> >       ut_assertok(i2c_emul_find(dev, &emul));
> > -     ut_assert(emul != NULL);
> > +     ut_assertnonnull(emul);
>
> This is an unrelated change. It would be preferable to describe it in
> the commit message.
>
> >
> >       old_base_time = sandbox_i2c_rtc_get_set_base_time(emul, 0);
> >
> >       ut_asserteq(0, sandbox_i2c_rtc_get_set_base_time(emul, -1));
> >
> > -     /* Resetting the RTC should put he base time back to normal */
> > +     /*
> > +      * Resetting the RTC should put the base time back to normal. Allow for
> > +      * a one-second adjustment in case the time flips over while this
> > +      * test process is pre-empted, since reset_time() in i2c_rtc_emul.c
> > +      * reads the time from the OS.
> > +      */
> >       ut_assertok(dm_rtc_reset(dev));
> >       base_time = sandbox_i2c_rtc_get_set_base_time(emul, -1);
> > -     ut_asserteq(old_base_time, base_time);
> > +     ut_assert(base_time - old_base_time <= 1);
>
> If the operating system uses daylight saving time, this may still fail
> (very rarely).
>
> How about using gmtime() instead of localtime()? But that would be a
> separate patch.

I'm not sure how to do this, as U-Boot expects local time. Of course
we could enhance the rtc API to support both (and use gmtime for the
test).

I've got an idea how to deal with daylight savings, and an alternative
approach for this patch, so will send a series.

>
> Reviewed-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>
> >
> >       return 0;
> >   }
>

Regards,
Simon