Re: [PATCH v4] time: Fix extra sleeptime injection when suspend fails

[Mukesh Ojha]

On 7/17/2018 2:31 AM, John Stultz wrote:
> On Mon, Jul 16, 2018 at 1:40 PM, Mukesh Ojha <mojha@xxxxxxxxxxxxxx> wrote:
> > Currently, there exists a corner case assuming when there is
> > only one clocksource e.g RTC, and system failed to go to
> > suspend mode. While resume rtc_resume() injects the sleeptime
> > as timekeeping_rtc_skipresume() returned 'false' (default value
> > of sleeptime_injected) due to which we can see mismatch in
> > timestamps.
> >
> > This issue can also come in a system where more than one
> > clocksource are present and very first suspend fails.
> >
> > Fix this by handling the sleeptime_injected flag properly.
> >
> > Success case:
> > ------------
> >                                          {sleeptime_injected=false}
> > rtc_suspend() => timekeeping_suspend() => timekeeping_resume() =>
> >
> > (sleeptime injected)
> >   rtc_resume()
> >
> > Failure case:
> > ------------
> >           {failure in sleep path} {sleeptime_injected=false}
> > rtc_suspend()     =>          rtc_resume()
> >
> > sleeptime injected again which was not required as the suspend failed)
> >
> > Originally-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Signed-off-by: Mukesh Ojha <mojha@xxxxxxxxxxxxxx>
> > ---
> > Changes in V4:
> >   * Changes as suggested by John
> >      - Changed the variable name from sleeptime_injected to suspend_timing_needed
> >      - Changed the boolean logic.
> Thanks so much for reworking and resending this again!
>
>
> > diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
> > index d37588f..ee455cc 100644
> > --- a/drivers/rtc/class.c
> > +++ b/drivers/rtc/class.c
> > @@ -102,7 +102,7 @@ static int rtc_resume(struct device *dev)
> >          struct timespec64       sleep_time;
> >          int err;
> >
> > -       if (timekeeping_rtc_skipresume())
> > +       if (!timekeeping_rtc_skipresume())
>
> Hrm... So I'd have instead inverted the logic *in*
> timekeeping_rtc_skipresume(), rather then here,  but this looks to be
> close enough and I can fix that bit up.

Will take care of yours and Thomas comment in v5.

> Can you confirm you've validated this version of the patch resolves
> the issue you reported?
Yeah, I validated.

Thanks
Mukesh


> thanks
> -john