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

[Nick Piggin]

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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