Re: Linux 2.4.19-rc3 (hyperthreading)

[J.A. Magallon]

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;
}