From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH] convert cnt32_to_63 to inline
Date: Tue, 11 Nov 2008 23:37:30 +0100
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To: David Howells <dhowells@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>, Nicolas Pitre <nico@cam.org>, Andrew Morton <akpm@linux-foundation.org>, torvalds@linux-foundation.org, rmk+lkml@arm.linux.org.uk, mingo@elte.hu, linux-kernel@vger.kernel.org, ralf@linux-mips.org, benh@kernel.crashing.org, paulus@samba.org, davem@davemloft.net, mingo@redhat.com, tglx@linutronix.de, rostedt@goodmis.org, linux-arch@vger.kernel.org

On Tue, 2008-11-11 at 22:31 +0000, David Howells wrote:
> Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
> 
> > @@ -52,18 +57,22 @@ unsigned long long sched_clock(void)
> > ...
> > +	preempt_disable_notrace();
> 
> Please, no!  sched_clock() is called with preemption or interrupts disabled
> everywhere except from some debugging code (lock tracing IIRC).  If you need
> to insert this preemption disablement somewhere, please insert it there.  At
> least then sched_clock() will be called consistently.

Agreed. You could do a WARN_ON(!in_atomic); in sched_clock() depending
on DEBUG_PREEMPT or something to ensure this.