[dev] spinlock implementation

[Manlio Perillo]

Hi.

I'm reading the nginx spinlock implementation, since I would like to use 
it in a separate project I'm working on.

The code is quite simple, however there is a thing I'm not sure to 
unserstand:
why ngx_cpu_pause is called only if Nginx detects that more than 1
cpu are in use?
Moreover the number of CPU is only detected for Free BSD.




Thanks  Manlio Perillo