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From: Lin Ming <ming.m.lin@intel.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: max_clock of the patch "sched_clock: fix cpu_clock()"
Date: Tue, 16 Sep 2008 11:01:37 +0800	[thread overview]
Message-ID: <1221534097.30750.20.camel@minggr> (raw)

Hi, Peter,

I have a question of the max_clock in below patch,
commit 354879bb977e06695993435745f06a0f6d39ce2b
Author: Peter Zijlstra <a.p.zijlstra@chello.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



             reply	other threads:[~2008-09-16  3:05 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-09-16  3:01 Lin Ming [this message]
2008-09-16  4:48 ` max_clock of the patch "sched_clock: fix cpu_clock()" Peter Zijlstra

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