Re: [PATCH][v2] timekeeping: Fix memory overwrite of sleep_time_bin array

Chen Yu
2016-07-19T08:59:28Z

Hi Thomas,

On 2016年07月19日 16:36, Thomas Gleixner wrote:
> On Tue, 19 Jul 2016, Chen Yu wrote:
>
>> It is reported the hibernation fails at 2nd attempt, which
>> hangs at hibernate() -> syscore_resume() -> i8237A_resume()
>> -> claim_dma_lock(), because the lock has already been taken.
>> However there is actually no other process would like to grab
>> this lock on that problematic platform.
>>
>> Further investigation shows that, the problem is caused by setting
>> /sys/power/pm_trace to 1 before the 1st hibernation, since once
>> pm_trace is enabled, the rtc becomes an unmeaningful value after resumed,
> So why is the RTC value useless if pm_trace is enabled? I really have a hard
> time to understand why pm_trace would affect the sleep time readout from RTC.
>
> Thanks,
>
> tglx
After pm_trace is enabled, during system suspend/hibernate, the hash name of
each devices will be written to rtc, so the rtc value depends on what
we write in last suspend
round, thus pm_trace can be used for diagnose which device failed to
suspend(eg, the suspending
on this device hang the system, we reboot the system , and check rtc
hash value).

In our case, after first hibernate/resume round, we found our current
system time
is at 2117, so syscore_resume -> timekeeping_resume :
__timekeeping_inject_sleeptime(tk, &ts_delta)
would inject a quite large delta : 2117 - 2017 year, thus the
sleep_time_bin is overflow.

thanks,
Yu