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

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Date:   Tue, 17 Jul 2018 11:59:11 +0530
From:   Mukesh Ojha <mojha@...eaurora.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        lkml <linux-kernel@...r.kernel.org>, gkohli@...eaurora.org,
        cpandya@...eaurora.org, neeraju@...eaurora.org
Subject: Re: [PATCH v4] time: Fix extra sleeptime injection when suspend fails



On 7/17/2018 2:31 AM, John Stultz wrote:
> On Mon, Jul 16, 2018 at 1:40 PM, Mukesh Ojha <mojha@...eaurora.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@...utronix.de>
>> Signed-off-by: Mukesh Ojha <mojha@...eaurora.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.

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