Re: [PATCH v2] introduce atomic_pointer to fix a race condition in cancelable mcs spinlocks

Paul E. McKenney
2014-06-06T15:15:27Z

On Fri, Jun 06, 2014 at 05:06:07PM +0200, Peter Zijlstra wrote:
> On Mon, Jun 02, 2014 at 10:09:35AM -0700, Linus Torvalds wrote:
> > On Mon, Jun 2, 2014 at 9:25 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > >
> > > And I can't say I'm a particular fan of these ops either, as alternative
> > > I'm almost inclined to just exclude parisc from using opt spinning.
> >
> > Please do.
>
> Something like so; if the rwsem stuff lands in .15 we need more for
> that, it doesn't have a convenient CONFIG symbol like this.
>
> Linus will you take this from email, or should I get it through
> tip/locking/urgent or so?
>
> ---
> Subject: locking, mutex: Disable optimistic spinning for PA-RISC
>
> PA-RISC's cmpxchg is not save against normal stores and the code used
> for optimistic spinning is known broken because of this.
>
> Disable for now.
>
> Reported-by: Mikulas Patocka <mpatocka@redhat.com>
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> ---
> kernel/Kconfig.locks | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/Kconfig.locks b/kernel/Kconfig.locks
> index 35536d9c0964..9c239e080c2d 100644
> --- a/kernel/Kconfig.locks
> +++ b/kernel/Kconfig.locks
> @@ -222,7 +222,7 @@ endif
>
> config MUTEX_SPIN_ON_OWNER
> def_bool y
> - depends on SMP && !DEBUG_MUTEXES
> + depends on SMP && !DEBUG_MUTEXES && !PARISC
>
> config ARCH_USE_QUEUE_RWLOCK
> bool
>