linux-kernel - Re: [patch 1/4] Ignore stolen time in the softlockup watchdog

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Date:	Tue, 24 Apr 2007 14:01:14 -0700
From:	Daniel Walker <dwalker@...sta.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Prarit Bhargava <prarit@...hat.com>,
	Rick Lindsley <ricklind@...ibm.com>,
	john stultz <johnstul@...ibm.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Eric Dumazet <dada1@...mosbay.com>,
	virtualization@...ts.osdl.org,
	Chris Lalancette <clalance@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 1/4] Ignore stolen time in the softlockup watchdog

On Tue, 2007-04-24 at 22:59 +0200, Ingo Molnar wrote:
> * Daniel Walker <dwalker@...sta.com> 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?
> 
> i concur. To me it appears not "absolutely correct" that someone 
> apparently added local_irq_save/restore to sched_clock(), but "absolute 
> madness". sched_clock() is _very_ performance-sensitive for the 
> scheduler, do not mess with it.

It looks like it's used in some sort of warp check, but only when
jiffies is used .. So I'm totally stumped why it's in there..

Daniel

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