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Date: Thu, 30 Nov 2006 01:35:31 -0800
From: Andrew Morton <akpm@osdl.org>
To: Ingo Molnar <mingo@redhat.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>,
       lkml <linux-kernel@vger.kernel.org>, ak@suse.de
Subject: Re: [PATCH -mm] x86_64 UP needs smp_call_function_single
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On Thu, 30 Nov 2006 10:22:20 +0100
Ingo Molnar <mingo@redhat.com> wrote:

> > 
> > btw, does anyone know why the SMP versions of this function use
> > spin_lock_bh(&call_lock)?
> 
> that makes no sense (neither the get_cpu()/put_cpu() gymnastics) if this
> is called with irqs disabled all the time.

smp_call_function_single() must be called with local interrupts ENabled.

But why isn't it just spin_lock()?

<looks>

Eric simply copied that code from ia64, which added the spin_lock_bh()
in 2.4.8.  Ho-hum.
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