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SubjectRe: 2.5.61: x86_64 num_online_cpus() buglet?
On Mon, Feb 17, 2003 at 06:51:12PM +0100, Mikael Pettersson wrote:
> Andi,
>
> Kernel 2.5.61's include/asm-x86_64/smp.h contains:
>
> extern unsigned long cpu_online_map;
> ...
> extern inline unsigned int num_online_cpus(void)
> {
> return hweight32(cpu_online_map);
> }
>
> and similarly for cpu_callout_map.
>
> hweight32() truncates a 64-bit operand to 32-bits, so either
> - the maps should be int rather than long, or
> - x86_64 needs to define and use a new hweight64(), or
> - CONFIG_NR_CPUS must not exceed 32 on x86_64.
>
> Comments?

You're right - it should use hweight64. Thanks for the headup.
I'll fix it.

Currently the x86-64 port is limited to 8 CPUs because the APIC
drivers don't support cluster mode (yet) and can only talk to 8
local apics, so it isn't that harmful.

-Andi
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