Messages in this thread | | | Subject | Re: [PATCH v2] time: Fix sleeptime injection for non-stop clocksource & persistent clock | From | Mukesh Ojha <> | Date | Mon, 25 Jun 2018 20:08:13 +0530 |
| |
Hi Thomas,
Thanks you very much for your time and reply.
On 6/23/2018 2:57 AM, Thomas Gleixner wrote: > 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.
Yeah, missed completely the fact that the issue can also come where only clocksource is RTC. > 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;
This will prevent first sleep failure.
> > /* 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;
This will prevent further extra sleeptime injection if sleep fails (valid for RTC only). Looks good!
> + > 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;
I did not get the exact valid point of moving it from `timekeeping_suspend` to `timekeeping_resume`. Although it will not have any side effect.
> + > raw_spin_lock_irqsave(&timekeeper_lock, flags); > write_seqcount_begin(&tk_core.seq); > timekeeping_forward_now(tk); >
Thanks for the change; will check and update.
Cheers, Mukesh
| |