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SubjectRe: [Q] Looking for an emulation for CMOV* instructions.
"Adam J. Richter" wrote:
> H. Peter Anvin wrote, in response to Andi Kleen:
> >You don't need CMPXCHG8B to do efficient inline mutexes. In fact, the
> >pthreads code for i386 uses the same mutexes the kernel does (LOCK INC
> >based, I believe), complete with section hacking to make them
> >efficiently inlinable -- and then they're put inside a function call.
> [...]
> 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.

Implementation detail. You could just as easily use a long instead of a
char and have room for 2^32 processors.

Brian Gerst
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