On Mon, Jul 16, 2018 at 9:17 AM, Mukesh Ojha <mo...@codeaurora.org> wrote: > On 7/13/2018 10:50 PM, John Stultz wrote: >> On Fri, Jul 13, 2018 at 12:13 AM, Mukesh Ojha <mo...@codeaurora.org> >>> On 7/11/2018 1:43 AM, John Stultz wrote: >>>> 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. >> >> So yea, I'm not saying logically the code is really any different, >> this is more of a naming nit. So instead of having a variable that is >> always on that we occasionally turn off, lets invert the naming and >> have it be a flag that we occasionally turn on. > > > I understand your concern about the name of the variable will be misleading. > But the changing Boolean state would not solve the actual issue. > > If i understand you correctly you meant below code > > diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c > index 32ae9ae..becc5bd 100644 > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -1523,7 +1523,7 @@ void __weak read_boot_clock64(struct timespec64 *ts) > * If a suspend fails before reaching timekeeping_resume() then the flag > * stays true and prevents erroneous sleeptime injection. > */ > -static bool sleeptime_injected = true; > +static bool suspend_timing_needed; > > /* Flag for if there is a persistent clock on this platform */ > static bool persistent_clock_exists; > @@ -1658,7 +1658,7 @@ void timekeeping_inject_sleeptime64(struct timespec64 > *delta) > raw_spin_lock_irqsave(&timekeeper_lock, flags); > write_seqcount_begin(&tk_core.seq); > > - sleeptime_injected = true; > + suspend_timing_needed = false; > > timekeeping_forward_now(tk); > > @@ -1714,10 +1714,10 @@ void timekeeping_resume(void) > tk->tkr_mono.mask); > nsec = mul_u64_u32_shr(cyc_delta, clock->mult, > clock->shift); > ts_delta = ns_to_timespec64(nsec); > - sleeptime_injected = true; > + suspend_timing_needed = true; > } else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > > 0) { > ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time); > - sleeptime_injected = true; > + suspend_timing_needed = true; > }
No no... This part is wrong. We only set suspend_timing_needed if we *didn't* calculate the suspend time in timekeeping_resume. You have to invert all the boolean logic for it to be equivalent. > if (sleeptime_injected) > @@ -1756,7 +1756,7 @@ int timekeeping_suspend(void) > if (timekeeping_suspend_time.tv_sec || > timekeeping_suspend_time.tv_nsec) > persistent_clock_exists = true; > > - sleeptime_injected = false; > + suspend_timing_needed = false; > > raw_spin_lock_irqsave(&timekeeper_lock, flags); > > > This has a problem.. > > >> >> Just the name sleeptime_injected is read a statement, which if we say >> is defaults to true, becomes confusing to think about when the >> timekeeping_suspend/resume code hasn't yet run (which is the case >> where your error cropped up) - and no sleeptime has actually been >> injected. > > > Yes, when very first suspend fails and timekeeping_suspend/resume did not > run ; That is the exact issue. > So, exact solution is no need to inject any sleeptime here. > > If we set the default value to false then we will see timekeeping_resume > will inject sleeptime by below code which was not intended. > > static int rtc_resume(struct device *dev) > { > struct rtc_device *rtc = to_rtc_device(dev); > struct rtc_time tm; > struct timespec64 new_system, new_rtc; > struct timespec64 sleep_time; > int err; > > if (timekeeping_rtc_skipresume()) // it will return the value false > as sleep failed and timekeeping_resume() did not get called. > return 0; > > <sleeptime injection happens here> So, I think with the logic bug above it will work out properly, but let me know if I'm still missing something. thanks -john