>
> Your comment prompted me to look at
> linux-2.5.2-pre11/include/asm-i386/spinlock.h, and I now believe that
> the "lock; decb" that it uses for grabbing spinlocks will return an
> incorrect success if 255 or more processors are waiting on the same
> spinlock. I don't know if anybody has ever built a shared memory x86
> multiprocessor with 257 (not a typo) or more CPU's, but it's possible
> to imagine. It's also possible to imagine this scenario happening
> with even just one processor and a preemtable kernel. I believe that
> the current preemtable kernel patch limits the number of preempted
> processes to something like four or six, but that's just a temporary
> limitation of the current version.
>
Linux specificially does not allow for more processors than there are
bits in a long (32 or 64). Libc, however, since it counts processes,
not CPUs, uses a 4-byte word.
-hpa
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