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

Steven Rostedt
2005-12-13T03:23:48Z

On Mon, 2005-12-12 at 16:57 -0800, Daniel Walker wrote:
> On Mon, 2005-12-12 at 23:45 +0000, David Howells wrote:
>
> > (1) Provides a simple xchg() based semaphore as a default for all
> > architectures that don't wish to override it and provide their own.
> >
> > Overriding is possible by setting CONFIG_ARCH_IMPLEMENTS_MUTEX and
> > supplying asm/mutex.h
> >
> > Partial overriding is possible by #defining mutex_grab(), mutex_release()
> > and is_mutex_locked() to perform the appropriate optimised functions.
>
> Your code is really similar to the RT mutex, which does everything that
> your mutex does at least ? Assuming you've reviewed the RT mutex, why
> would we want to use yours over it?

Maybe this would be the better !PREEMPT_RT version. But the true mutex
that Ingo is making would be used for the PREEMPT_RT side.

This code at least brings down the over head of semaphores where they
are not really needed. Looking at the code slightly (I must admit, I
spent maybe 30 seconds looking at it), it does seem a little similar to
Ingo's. Could just be coincidence, since the methods are pretty much
what multiple people would come up with. But you both work for RedHat,
hmm.

-- Steve