linux-kernel - Re: [PATCH][v2] timekeeping: Fix memory overwrite of sleep_time

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Date:	Tue, 19 Jul 2016 10:36:20 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Chen Yu <yu.c.chen@...el.com>
cc:	John Stultz <john.stultz@...aro.org>,
	"Rafael J. Wysock" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	"Stable # 3 . 17+" <stable@...r.kernel.org>
Subject: Re: [PATCH][v2] timekeeping: Fix memory overwrite of sleep_time_bin
 array

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