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

[Linh Dang]

Russell King <rmk+lkml@xxxxxxxxxxxxxxxx> wrote:

> On Sat, Dec 17, 2005 at 12:01:27AM +1100, Nick Piggin wrote:
>> You were proposing a worse default, which is the reason I suggested
>> it.
>
> I'd like to qualify that.  "for architectures with native cmpxchg".
>
> For general consumption (not specifically related to mutex stuff)...
>
> For architectures with llsc, sequences stuch as:
>
> 	load
> 	modify
> 	cmpxchg
>
> are inefficient because they have to be implemented as:
>
> 	load
> 	modify
> 	load
> 	compare
> 	store conditional
>

I dont know what arch u have in mind but for ppc it is:

        load-reserve
        modify
        store-conditional

and NOT the sequence you show.

-- 
Linh Dang
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