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

[Nick Piggin]

David Howells wrote:
> Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:
>
>
> > We have atomic_cmpxchg. Can you use that for a sufficient generic
> > implementation?
>
>
> No. CMPXCHG/CAS is not as available as XCHG, and it's also unnecessary.

atomic_cmpxchg should be available on all platforms.

While it may be strictly unnecessary, if it can be used to avoid
having a crappy default implementation that requires it to be
reimplemented in all architectures then that would be a good thing.

Any arguments about bad scalability or RT behaviour of the hashed
spinlock emulation atomic_t implementations are silly because they
are used by all atomic_ operations. It is an arch implementation
detail that generic code should not have to worry about.

--
SUSE Labs, Novell Inc.

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