MIPS atomic operations, "sync"

Hi,

I am currently creating a "LOCK" prefix free and memory barrier free version
of atomic.h to fulfill my tracer (LTTng) needs, which is to atomically update
per-cpu data and have a minimal performance loss.

I just came across the MIPS atomic.h and system.h implementations in 2.6.18
which brings a question :

Why are the primitives in include/asm-mips/atomic.h using the "sync"
instruction even in the UP case ? system.h cmpxchg only uses the sync in the
SMP case.

Mathieu


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