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 <[email protected]>
Signed-off-by: Mukesh Ojha <[email protected]>
---
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
On Tue, 17 Jul 2018, Mukesh Ojha wrote:
> @@ -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;
That does not make any sense at all, really.
> /* 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;
Just make this !suspend_timing_needed and the function name and its return
value still makes sense.
> @@ -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);
This reads odd as well. I'd rather keep a local variable inject_sleeptime
or such and set that in the code pathes above.
if (...) {
...
inject_sleeptime = true;
} else if (...) {
...
inject_sleeptime = true;
}
if (inject_sleeptime) {
suspend_timing_needed = false;
__timekeeping_inject_sleeptime();
}
Hmm? Just blindly converting everything results in functional, but
nonsensical code. Think about what happens when you look at that stuff 6
month from now...
Thanks,
tglx
On Mon, Jul 16, 2018 at 1:40 PM, Mukesh Ojha <[email protected]> wrote:
> 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 <[email protected]>
> Signed-off-by: Mukesh Ojha <[email protected]>
> ---
> Changes in V4:
> * Changes as suggested by John
> - Changed the variable name from sleeptime_injected to suspend_timing_needed
> - Changed the boolean logic.
Thanks so much for reworking and resending this again!
> 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())
Hrm... So I'd have instead inverted the logic *in*
timekeeping_rtc_skipresume(), rather then here, but this looks to be
close enough and I can fix that bit up.
Can you confirm you've validated this version of the patch resolves
the issue you reported?
thanks
-john
On 7/17/2018 2:20 AM, Thomas Gleixner wrote:
> On Tue, 17 Jul 2018, Mukesh Ojha wrote:
>> @@ -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;
> That does not make any sense at all, really.
>
>> /* 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;
> Just make this !suspend_timing_needed and the function name and its return
> value still makes sense.
>
>> @@ -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);
> This reads odd as well. I'd rather keep a local variable inject_sleeptime
> or such and set that in the code pathes above.
>
> if (...) {
> ...
> inject_sleeptime = true;
> } else if (...) {
> ...
> inject_sleeptime = true;
> }
>
> if (inject_sleeptime) {
> suspend_timing_needed = false;
> __timekeeping_inject_sleeptime();
> }
Will do suggested change and send in v5.
Thanks.
>
> Hmm? Just blindly converting everything results in functional, but
> nonsensical code. Think about what happens when you look at that stuff 6
> month from now...
>
> Thanks,
>
> tglx
>
On 7/17/2018 2:31 AM, John Stultz wrote:
> On Mon, Jul 16, 2018 at 1:40 PM, Mukesh Ojha <[email protected]> wrote:
>> 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 <[email protected]>
>> Signed-off-by: Mukesh Ojha <[email protected]>
>> ---
>> Changes in V4:
>> * Changes as suggested by John
>> - Changed the variable name from sleeptime_injected to suspend_timing_needed
>> - Changed the boolean logic.
> Thanks so much for reworking and resending this again!
>
>
>> 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())
>
> Hrm... So I'd have instead inverted the logic *in*
> timekeeping_rtc_skipresume(), rather then here, but this looks to be
> close enough and I can fix that bit up.
Will take care of yours and Thomas comment in v5.
>
> Can you confirm you've validated this version of the patch resolves
> the issue you reported?
Yeah, I validated.
Thanks
Mukesh
>
> thanks
> -john