Re: [PATCH 1/19] MUTEX: Introduce simple mutex implementation

Nick Piggin
2005-12-16T15:35:14Z

Linh Dang wrote:

>>Do you now see what I mean? (yup, ARM is a llsc architecture.)
>
>
> Well, it may be true for ARM but for ppc (i dunno what exactly llsc
> means but someone in the thread put ppc in llsc group) it's:
>

load locked or load with lock, IIRC.

> loop:
> load-reserve foo => old
> new = old * N
> store-conditional new => foo
> if failed goto loop
>

The point is that the typical use case for a cmpxchg is less optimal
if cmpxchg is simulated with llsc than if the same functionality were
directly implemented with llsc instructions.

--
SUSE Labs, Novell Inc.

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