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

Linh Dang
2005-12-16T13:46:44Z

Russell King <rmk+lkml@arm.linux.org.uk> 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