Re: [PATCH 1/1] mm: Prevent dereferencing non-allocated per_cpu variables

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On 27 Nov 2007 at 13:50, travis@xxxxxxx wrote:

> Change loops controlled by 'for (i = 0; i < NR_CPUS; i++)' to use
> 'for_each_possible_cpu(i)' when there's a _remote possibility_ of
> dereferencing a non-allocated per_cpu variable involved.

actually, it's not that remote, it happens every time
NR_CPUS > num_possible_cpus(). i ran into this myself
on a dual core box with NR_CPUS=4. due to my rewrite
of the i386 per-cpu segment handling, i actually got
a NULL deref where the vanilla kernel would be accessing
the area of [__per_cpu_start, __per_cpu_end] for each
non-possible CPU (which doesn't crash per se but is
still not correct somehow i think).

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