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From:   John Stultz <john.stultz@linaro.org>
Date:   Mon, 16 Jul 2018 14:01:41 -0700
Message-ID: <CALAqxLVMaU4FJ1xu78ow=FwSbmQObw0-HGBUTpgr27vjKTOqrw@mail.gmail.com>
Subject: Re: [PATCH v4] time: Fix extra sleeptime injection when suspend fails
To:     Mukesh Ojha <mojha@codeaurora.org>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        lkml <linux-kernel@vger.kernel.org>, gkohli@codeaurora.org,
        cpandya@codeaurora.org, neeraju@codeaurora.org
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On Mon, Jul 16, 2018 at 1:40 PM, Mukesh Ojha <mojha@codeaurora.org> 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@linutronix.de>
> Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>
> ---
> 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.

Can you confirm you've validated this version of the patch resolves
the issue you reported?

thanks
-john