linux-kernel - max_clock of the patch "sched_clock: fix cpu

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Message-Id: <1221534097.30750.20.camel@minggr>
Date:	Tue, 16 Sep 2008 11:01:37 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: max_clock of the patch "sched_clock: fix cpu_clock()"

Hi, Peter,

I have a question of the max_clock in below patch,
commit 354879bb977e06695993435745f06a0f6d39ce2b
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date:   Mon Aug 25 17:15:34 2008 +0200

    sched_clock: fix cpu_clock()

The original code to calculate min_clock and max_clock is,
min_clock = scd->tick_gtod + delta_jiffies * TICK_NSEC;
max_clock = min_clock + TICK_NSEC;

Now it's changed to,
min_clock = wrap_max(scd->tick_gtod, scd->clock);
max_clock = scd->tick_gtod + TICK_NSEC;

Is this max_clock still correct if, in a rare case, irq is disabled for
many ticks?

Thanks,
Lin Ming


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