Messages in this thread Patch in this message |  | | Date | Fri, 22 Jun 2018 23:27:16 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v2] time: Fix sleeptime injection for non-stop clocksource & persistent clock |
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On Wed, 30 May 2018, 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()
I can see the problem.
> Signed-off-by: Mukesh Ojha <mojha@codeaurora.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;
But this is really a horrible hack. The right thing to do is to keep track whether timekeeping_suspend() has been reached in the first place. There is a very simple way to do that. Uncompiled and completely untested patch below, but you get the idea.
Thanks,
tglx
8<------------------- diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 4786df904c22..32ae9aea61c3 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; /* Flag for if there is a persistent clock on this platform */ static bool persistent_clock_exists; @@ -1646,6 +1658,8 @@ void timekeeping_inject_sleeptime64(struct timespec64 *delta) raw_spin_lock_irqsave(&timekeeper_lock, flags); write_seqcount_begin(&tk_core.seq); + sleeptime_injected = true; + timekeeping_forward_now(tk); __timekeeping_inject_sleeptime(tk, delta); @@ -1671,7 +1685,6 @@ void timekeeping_resume(void) struct timespec64 ts_new, ts_delta; u64 cycle_now; - sleeptime_injected = false; read_persistent_clock64(&ts_new); clockevents_resume(); @@ -1743,6 +1756,8 @@ int timekeeping_suspend(void) if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec) persistent_clock_exists = true; + sleeptime_injected = false; + raw_spin_lock_irqsave(&timekeeper_lock, flags); write_seqcount_begin(&tk_core.seq); timekeeping_forward_now(tk);
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