From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Lin Ming <ming.m.lin@intel.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: max_clock of the patch "sched_clock: fix cpu_clock()"
Date: Tue, 16 Sep 2008 06:48:30 +0200 [thread overview]
Message-ID: <1221540510.6943.1.camel@lappy.programming.kicks-ass.net> (raw)
In-Reply-To: <1221534097.30750.20.camel@minggr>
On Tue, 2008-09-16 at 11:01 +0800, Lin Ming wrote:
> 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?
Nope, it wont (nor would the old), but having irqs disabled for that
long would be something worth fixing.
prev parent reply other threads:[~2008-09-16 4:49 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-16 3:01 max_clock of the patch "sched_clock: fix cpu_clock()" Lin Ming
2008-09-16 4:48 ` Peter Zijlstra [this message]
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