On Fri, Jul 6, 2018 at 6:17 AM, Mukesh Ojha <[email protected]> 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 <[email protected]> > Signed-off-by: Mukesh Ojha <[email protected]> > --- > 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 think that will help make things a bit more clear, no? thanks -john
