linux-kernel - Re: [PATCH v2] time: Fix sleeptime injection for non-stop clocksource & persistent clock

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Message-ID: <19644aab-d5dc-aace-48da-5df1587da873@codeaurora.org>
Date:   Thu, 14 Jun 2018 19:37:28 +0530
From:   Mukesh Ojha <mojha@...eaurora.org>
To:     john.stultz@...aro.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org
Cc:     neeraju@...eaurora.org, gkohli@...eaurora.org,
        cpandya@...eaurora.org
Subject: Re: [PATCH v2] time: Fix sleeptime injection for non-stop clocksource
 & persistent clock

Any input on this ?

Thanks,
Mukesh
On 5/30/2018 5:14 PM, Mukesh Ojha wrote:
> Currently, for both non-stop clocksource and persistent clock
> there is a corner case, when a driver failed to go suspend mode.
> rtc_resume() injects the sleeptime as timekeeping_rtc_skipresume()
> returned 'false'(sleeptime_injected=false) due to which we can
> see mismatch in timestamps between system clock and other timers.
>
> Fix this by updating sleeptime_injected=true for both non-stop
> clocksource and persistent clock.
>
> Success case:
> ------------
>                                           {sleeptime_injected=true}
> rtc_suspend() => timekeeping_suspend() => timekeeping_resume() =>
>    rtc_resume()
>
> Failure case:
> ------------
>               {failure in sleep path} {sleeptime_injected=false}
> rtc_suspend()          =>            rtc_resume()
>
> Signed-off-by: Mukesh Ojha <mojha@...eaurora.org>
> ---
> Changes in v2:
>   * Updated the commit text.
>   * Removed extra variable and used the earlier static
>     variable 'sleeptime_injected'.
>
>   kernel/time/timekeeping.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
>
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 49cbcee..2754c1b 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -1610,6 +1610,17 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
>    */
>   bool timekeeping_rtc_skipresume(void)
>   {
> +	struct timekeeper *tk = &tk_core.timekeeper;
> +	/*
> +	 * This is to ensure that we don't end up injecting
> +	 * the sleeptime via rtc_resume() for non-stop clocksource
> +	 * when we fail to sleep.
> +	 */
> +	if (!sleeptime_injected)
> +		sleeptime_injected = ((tk->tkr_mono.clock->flags &
> +			CLOCK_SOURCE_SUSPEND_NONSTOP) ||
> +			(persistent_clock_exists)) ? true : false;
> +
>   	return sleeptime_injected;
>   }
>