Messages in this thread | | | Subject | Re: [PATCH v3] time: Fix incorrect sleeptime injection when suspend fails | From | Mukesh Ojha <> | Date | Tue, 17 Jul 2018 00:00:26 +0530 |
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On 7/16/2018 10:44 PM, John Stultz wrote: > On Mon, Jul 16, 2018 at 9:30 AM, John Stultz <john.stultz@linaro.org> wrote: >> On Mon, Jul 16, 2018 at 9:17 AM, Mukesh Ojha <mojha@codeaurora.org> wrote: >>> On 7/13/2018 10:50 PM, John Stultz wrote: >>>> On Fri, Jul 13, 2018 at 12:13 AM, Mukesh Ojha <mojha@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. >> > ... >>> <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.
Please give it thought to a case where very first suspend fails with your logic. If i am not able to get your thought, please write a patch.
-Mukesh
> Sorry, I meant "with the logic bug above fixed it will work out". > > thanks > -john
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