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Date: Sun, 12 Dec 2004 22:13:27 -0800
From: Andrew Morton <akpm@osdl.org>
To: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Cc: paulmck@us.ibm.com, sfr@canb.auug.org.au, linux-kernel@vger.kernel.org,
       dipankar@in.ibm.com, shaohua.li@intel.com, len.brown@intel.com
Subject: Re: [PATCH] Remove RCU abuse in cpu_idle()
Message-Id: <20041212221327.375fa4d0.akpm@osdl.org>
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Zwane Mwaikambo <zwane@arm.linux.org.uk> wrote:
>
> On Sat, 11 Dec 2004, Zwane Mwaikambo wrote:
> 
> > > Introduce cpu_idle_wait() on architectures requiring modification of 
> > > pm_idle from modules, this will ensure that all processors have updated 
> > > their cached values of pm_idle upon exit. This patch is to address the bug 
> > > report at http://bugme.osdl.org/show_bug.cgi?id=1716 and replaces the 
> > > current code fix which is in violation of normal RCU usage as pointed out 
> > > by Stephen, Dipankar and Paul.
> 
> ...
> 
>  void cpu_idle (void)
>  {
> +	int cpu = smp_processor_id();
> +
>  	/* endless idle loop with no priority at all */

This gives me scadzillions of "using smp_procesor_id() in preemptible"
warnings.

I'll shut that up with _smp_processor_id() but one does wonder what happens
if we get preempted and `cpu' refers to some other CPU?