linux-kernel - Re: [PATCH 0/2] Make the TSC safe to be used by gettimeofday().

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Message-ID: <41840b750611140430k3b46023dr9a01b8b38bbb535d@mail.gmail.com>
Date:	Tue, 14 Nov 2006 14:30:38 +0200
From:	"Shem Multinymous" <multinymous@...il.com>
To:	"Suleiman Souhlal" <ssouhlal@...ebsd.org>
Cc:	"Andi Kleen" <ak@...e.de>,
	"Linux Kernel ML" <linux-kernel@...r.kernel.org>, vojtech@...e.cz,
	"Jiri Bohac" <jbohac@...e.cz>,
	"Nigel Cunningham" <ncunningham@...lades.com>,
	"Pavel Machek" <pavel@...e.cz>
Subject: Re: [PATCH 0/2] Make the TSC safe to be used by gettimeofday().

On 11/14/06, Suleiman Souhlal <ssouhlal@...ebsd.org> wrote:
> I believe that the results returned will always be monotonic, as long as
> the frequency of the TSC does not change from under us (that is, without
> the kernel knowing). This is because we "synchronize" each CPU's vxtime
> with a global time source (HPET) every time we know the TSC rate changes.

Does this hold after a suspend/resume cycle? You could be resuming
with a different CPU clock than what you suspended with, and I'm not
sure anything guarantees an early enough re-sync.

  Shem
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