From: Andi Kleen <ak@suse.de>
To: virtualization@lists.linux-foundation.org
Cc: Daniel Walker <dwalker@mvista.com>,
Jeremy Fitzhardinge <jeremy@goop.org>,
Prarit Bhargava <prarit@redhat.com>,
Rick Lindsley <ricklind@us.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
john stultz <johnstul@us.ibm.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Eric Dumazet <dada1@cosmosbay.com>,
virtualization@lists.osdl.org,
Chris Lalancette <clalance@redhat.com>,
Paul Mackerras <paulus@samba.org>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch 1/4] Ignore stolen time in the softlockup watchdog
Date: Tue, 24 Apr 2007 23:20:06 +0200 [thread overview]
Message-ID: <200704242320.06470.ak@suse.de> (raw)
In-Reply-To: <1177447948.12796.66.camel@imap.mvista.com>
On Tuesday 24 April 2007 22:52:27 Daniel Walker wrote:
> On Tue, 2007-04-24 at 13:24 -0700, Jeremy Fitzhardinge wrote:
>
> > And sched_clock's use of local_irq_save/restore appears to be absolutely
> > correct, so I think it must be triggering a bug in either the self-tests
> > or lockdep itself.
>
> Why does sched_clock need to disable interrupts?
It's only used in the instable path which is kind of "i already threw up
my hands" anyways
I use it because when you transition from stable (TSC) to instable (jiffies)
the only way to avoid the clock jumping backwards is to remember and update the
last value. To avoid races with parallel cpufreq handlers or timer
interrupts this small section needs to run with interrupts disabled.
The alternative would be a seqlock, but people have complained about this
earlier too so i judged irq disabling better.
-Andi
next prev parent reply other threads:[~2007-04-24 21:20 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-27 21:49 [patch 0/4] Revised softlockup watchdog improvement patches Jeremy Fitzhardinge
2007-03-27 21:49 ` [patch 1/4] Ignore stolen time in the softlockup watchdog Jeremy Fitzhardinge
2007-04-24 6:49 ` Andrew Morton
2007-04-24 6:58 ` Jeremy Fitzhardinge
2007-04-24 7:09 ` Andrew Morton
2007-04-24 17:51 ` Jeremy Fitzhardinge
2007-04-24 17:57 ` Andrew Morton
2007-04-24 18:16 ` Jeremy Fitzhardinge
2007-04-24 18:32 ` Andrew Morton
2007-04-24 20:00 ` Jeremy Fitzhardinge
2007-04-24 20:14 ` Andrew Morton
2007-04-24 20:46 ` Jeremy Fitzhardinge
2007-04-24 20:24 ` Jeremy Fitzhardinge
2007-04-24 20:33 ` Andrew Morton
2007-04-24 20:48 ` Jeremy Fitzhardinge
2007-04-24 20:52 ` Daniel Walker
2007-04-24 20:59 ` Ingo Molnar
2007-04-24 21:01 ` Daniel Walker
2007-04-24 21:14 ` Andrew Morton
2007-04-24 21:20 ` Andi Kleen [this message]
2007-04-24 21:33 ` Daniel Walker
2007-03-27 21:49 ` [patch 2/4] percpu enable flag for " Jeremy Fitzhardinge
2007-03-27 21:49 ` [patch 3/4] Locally disable the softlockup watchdog rather than touching it Jeremy Fitzhardinge
2007-03-28 13:33 ` Prarit Bhargava
2007-03-28 13:50 ` Andi Kleen
2007-03-28 14:00 ` Prarit Bhargava
2007-03-28 14:09 ` Andi Kleen
2007-03-28 14:13 ` Prarit Bhargava
2007-03-28 14:44 ` Jeremy Fitzhardinge
2007-03-28 14:51 ` Prarit Bhargava
2007-03-28 15:22 ` Jeremy Fitzhardinge
2007-03-28 15:27 ` Prarit Bhargava
2007-03-27 21:49 ` [patch 4/4] Add global disable/enable for softlockup watchdog Jeremy Fitzhardinge
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