linux-kernel - Re: [PATCH -mm] x86_64 UP needs smp_call_function

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Message-Id: <20061130013531.6bb73f53.akpm@osdl.org>
Date:	Thu, 30 Nov 2006 01:35:31 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	Randy Dunlap <randy.dunlap@...cle.com>,
	lkml <linux-kernel@...r.kernel.org>, ak@...e.de
Subject: Re: [PATCH -mm] x86_64 UP needs smp_call_function_single

On Thu, 30 Nov 2006 10:22:20 +0100
Ingo Molnar <mingo@...hat.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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