Re: [patch] spinlocks: remove 'volatile'

J.A. Magallón
2006-07-07T22:49:57Z

On Fri, 7 Jul 2006 17:22:22 -0500 (CDT), Chase Venters <chase.venters@clientec.com> wrote:

> > .L7:
> > movl $1, mtx <=========
> > movl spinvar, %eax
> > movl $0, mtx <=========
> > testl %eax, %eax
> > jne .L7
> > popl %ebp
> > ret
>
> NO! It's not better. You're still not syncing or locking the bus! If you
> refer to the fact that the "movl $1" has magically appeared, that's
> because you've just PAPERED OVER THE PROBLEM WITH "volatile", which is
> _exactly_ what Linus is telling you NOT TO DO.
>

BTW, I really don't mind if a given architecnture has to lock the bus or
say a prayer to Budha to reload a variable. I want it to be reloaded at
every (or a certain, in case of a (volatile)mtx cast) usage. The compiler
is the responsible of knowing what to do. What if nextgen P4 Xeon do not
need a bus lock ? Will you rewrite the kernel ?

--
J.A. Magallon <jamagallon()ono!com> \ Software is like sex:
\ It's better when it's free
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