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Date: Tue, 30 Jul 2002 02:09:12 +0200
From: "J.A. Magallon" <jamagallon@able.es>
To: Rik van Riel <riel@conectiva.com.br>
Cc: Andrea Arcangeli <andrea@suse.de>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Andrew Theurer <habanero@us.ibm.com>, linux-kernel@vger.kernel.org,
       Marcelo Tosatti <marcelo@conectiva.com.br>
Subject: Re: Linux 2.4.19-rc3 (hyperthreading)
Message-ID: <20020730000912.GA6406@714-cm.cps.unizar.es>
References: <Pine.LNX.4.44L.0207292051040.3086-100000@imladris.surriel.com>
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On 20020730 Rik van Riel wrote:
> On Tue, 30 Jul 2002, Andrea Arcangeli wrote:
> 
> > and the new one had a bug too :). Please merge the fix I posted to l-k
> > too thanks.
> 
> Judging from the patch the code seems incredibly subtle and
> I'd be amazed if it doesn't break again every few weeks...
> 

How about this version (gcc-3.2 generates the same amount of assembler):

int find(int this_cpu)
{
    int i;

    for (   i = (this_cpu+1)%smp_num_cpus;
            i != this_cpu;
            i = (i+1)%smp_num_cpus  )
    {
        int physical = cpu_logical_map(i);
        int sibling = cpu_sibling_map[physical];

        if (idle_cpu(physical) && idle_cpu(sibling))
            return physical;
    }
    return -1;
}

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