Messages in this thread | | | Subject | Re: [PATCH v3] time: Fix incorrect sleeptime injection when suspend fails | From | Mukesh Ojha <> | Date | Fri, 13 Jul 2018 12:43:24 +0530 |
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Hi John,
Thanks for your response Please find my comments inline.
On 7/11/2018 1:43 AM, John Stultz wrote: > On Fri, Jul 6, 2018 at 6:17 AM, 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 `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 v3: >> * Updated commit subject and description. >> * Updated the patch as per the fix given by Thomas Gleixner. >> >> Changes in v2: >> * Updated the commit text. >> * Removed extra variable and used the earlier static >> variable 'sleeptime_injected'. >> >> kernel/time/timekeeping.c | 21 ++++++++++++++++++--- >> 1 file changed, 18 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c >> index 4786df9..32ae9ae 100644 >> --- a/kernel/time/timekeeping.c >> +++ b/kernel/time/timekeeping.c >> @@ -1510,8 +1510,20 @@ void __weak read_boot_clock64(struct timespec64 *ts) >> ts->tv_nsec = 0; >> } >> >> -/* Flag for if timekeeping_resume() has injected sleeptime */ >> -static bool sleeptime_injected; >> +/* >> + * Flag reflecting whether timekeeping_resume() has injected sleeptime. >> + * >> + * The flag starts of true and is only cleared when a suspend reaches >> + * timekeeping_suspend(), timekeeping_resume() sets it when the timekeeper >> + * clocksource is not stopping across suspend and has been used to update >> + * sleep time. If the timekeeper clocksource has stopped then the flag >> + * stays false and is used by the RTC resume code to decide whether sleep >> + * time must be injected and if so the flag gets set then. >> + * >> + * If a suspend fails before reaching timekeeping_resume() then the flag >> + * stays true and prevents erroneous sleeptime injection. >> + */ >> +static bool sleeptime_injected = true; > I worry this upside-down logic is too subtle to be easily reasoned > about, and will just lead to future mistakes. > > Can we instead call this "suspend_timing_needed" and only set it to > true when we don't inject any sleep time on resume?
I did not get your point "only set it to true when we don't inject any sleep time on resume? " How do we know this ? This question itself depends on the "sleeptime_injected" if it is true means no need to inject else need to inject.
Also, we need to make this variable back and forth true, false; suspends path ensures it to make it false.
Just to add here there are already two path where `sleeptime_injected` set to true one from NON-stop clocksource and other from persistant clock and the RTC one was missing, so we are adding with this patch.
Cheers, -Mukesh
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