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Date: Wed, 27 Jan 2016 10:39:17 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Prarit Bhargava <prarit@redhat.com>
cc: linux-kernel@vger.kernel.org, John Stultz <john.stultz@linaro.org>,
        Xunlei Pang <pang.xunlei@linaro.org>,
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        Peter Hurley <peter@hurleysoftware.com>,
        Vasily Averin <vvs@virtuozzo.com>, Joe Perches <joe@perches.com>
Subject: Re: [PATCH] printk, allow different timestamps for printk.time
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On Tue, 26 Jan 2016, Prarit Bhargava wrote:
> On 01/26/2016 03:34 PM, Thomas Gleixner wrote:
> > Just for the record: The fast timekeeper stops across the inner workings of
> > suspend/resume. But I think that doesn't matter much.
> 
> I've had to debug s/r before using the sysfs interface.  It is nice to have that
> with a proper timestamp because a lot of the failures are in the driver suspend
> and resume paths.  I could easily change the options to:

The timekeeper suspends/resumes in the syscore section, so the driver part is
not affected.
 
> 0 = disable
> 1 = local clock (which along with 0 would maintain the current state of things)
> 2 = monotonic
> 3 = real

Yes, that works.

Btw, you need to document, that REAL can occasionally provide a wrong value on
32bit machines in case that a concurrent update of the realtime offset happens
(settimeofday, leap seconds ...). That's because we access real_offset w/o the
seqcount protection. It's probably hard to achieve, but it might happen.

Thanks,

	tglx