Messages in this thread Patch in this message | | | From | Mukesh Ojha <> | Subject | [PATCH v4] time: Fix extra sleeptime injection when suspend fails | Date | Tue, 17 Jul 2018 02:10:50 +0530 |
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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 the 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 <tglx@linutronix.de> Signed-off-by: Mukesh Ojha <mojha@codeaurora.org> --- Changes in V4: * Changes as suggested by John - Changed the variable name from sleeptime_injected to suspend_timing_needed - Changed the boolean logic. 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'. drivers/rtc/class.c | 2 +- kernel/time/timekeeping.c | 29 ++++++++++++++++++++++------- 2 files changed, 23 insertions(+), 8 deletions(-)
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index d37588f..ee455cc 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -102,7 +102,7 @@ static int rtc_resume(struct device *dev) struct timespec64 sleep_time; int err; - if (timekeeping_rtc_skipresume()) + if (!timekeeping_rtc_skipresume()) return 0; rtc_hctosys_ret = -ENODEV; diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 4786df9..b25f771 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 false and is only set when a suspend reaches + * timekeeping_suspend(), timekeeping_resume() sets it to false 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 true and is used by the RTC resume code to decide + * whether sleeptime must be injected and if so the flag gets false then. + * + * If a suspend fails before reaching timekeeping_resume() then the flag + * stays false and prevents erroneous sleeptime injection. + */ +static bool suspend_timing_needed; /* Flag for if there is a persistent clock on this platform */ static bool persistent_clock_exists; @@ -1610,7 +1622,7 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk, */ bool timekeeping_rtc_skipresume(void) { - return sleeptime_injected; + return suspend_timing_needed; } /** @@ -1646,6 +1658,8 @@ void timekeeping_inject_sleeptime64(struct timespec64 *delta) raw_spin_lock_irqsave(&timekeeper_lock, flags); write_seqcount_begin(&tk_core.seq); + suspend_timing_needed = false; + 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(); @@ -1701,13 +1714,13 @@ 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 = false; } 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 = false; } - if (sleeptime_injected) + if (!suspend_timing_needed) __timekeeping_inject_sleeptime(tk, &ts_delta); /* Re-base the last cycle value */ @@ -1743,6 +1756,8 @@ int timekeeping_suspend(void) if (timekeeping_suspend_time.tv_sec || timekeeping_suspend_time.tv_nsec) persistent_clock_exists = true; + suspend_timing_needed = true; + raw_spin_lock_irqsave(&timekeeper_lock, flags); write_seqcount_begin(&tk_core.seq); timekeeping_forward_now(tk); -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
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