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()
Signed-off-by: Mukesh Ojha <[email protected]>
---
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;
+
return sleeptime_injected;
}
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
Any input on this ?
Thanks,
Mukesh
On 5/30/2018 5:14 PM, 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()
>
> Signed-off-by: Mukesh Ojha <[email protected]>
> ---
> 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;
> +
> return sleeptime_injected;
> }
>
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 <[email protected]>
> ---
> 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.
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;
/* 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;
+
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;
+
raw_spin_lock_irqsave(&timekeeper_lock, flags);
write_seqcount_begin(&tk_core.seq);
timekeeping_forward_now(tk);
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 <[email protected]>
>> ---
>> 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
On Mon, 25 Jun 2018, Mukesh Ojha wrote:
> On 6/23/2018 2:57 AM, Thomas Gleixner wrote:
> > @@ -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`.
It's the other way round. I move it from resume to suspend. Simply because
it should only be set to 'false' when suspend is reached. It would work the
other way round as well, but I felt it's inconsistent.
Thanks,
tglx
Hi Thomas,
Could you raise a formal patch on this as you are the author now?
Thanks,
Mukesh
On 6/25/2018 8:34 PM, Thomas Gleixner wrote:
> On Mon, 25 Jun 2018, Mukesh Ojha wrote:
>> On 6/23/2018 2:57 AM, Thomas Gleixner wrote:
>>> @@ -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`.
> It's the other way round. I move it from resume to suspend. Simply because
> it should only be set to 'false' when suspend is reached. It would work the
> other way round as well, but I felt it's inconsistent.
>
> Thanks,
>
> tglx
>
>
On Fri, 6 Jul 2018, Mukesh Ojha wrote:
> Hi Thomas,
>
> Could you raise a formal patch on this as you are the author now?
I'm short of cycles ATM. Feel free to pick it up and write a nice
changelog. Just add
Originally-by: Thomas Gleixner <[email protected]>
Thanks,
tglx