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

[Nick Piggin]

David Howells wrote:
> Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote:
>
>
> > atomic_cmpxchg should be available on all platforms.
>
>
> Two points:
>
>  (1) If it's using spinlocks, then it's pointless to use atomic_cmpxchg.

Why?

>  (2) atomic_t is a 32-bit type, and on a 64-bit platform I will want a 64-bit
>      type so that I can stick the owner address in there (I've got a second
>      variant not yet released).

I'm sure you could use a seperate field as it would be a debug
option, right?

But atomic longs are coming along and it is probably feasable to
do 64-bit atomic_cmpxchg on all 64-bit word architectures if you
really needed that.

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