Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-07

Herbert Xu
2005-03-23T09:48:53Z

On Wed, Mar 23, 2005 at 08:40:58PM +1100, Herbert Xu wrote:
> Paul E. McKenney <paulmck@us.ibm.com> wrote:
> >
> > +void rcu_read_unlock(void)
> > +{
> > + int cpu;
> > +
> > + if (--current->rcu_read_lock_nesting == 0) {
> > + atomic_dec(&current->rcu_data->active_readers);
> > + /*
> > + * Check whether we have reached quiescent state.
> > + * Note! This is only for the local CPU, not for
> > + * current->rcu_data's CPU [which typically is the
> > + * current CPU, but may also be another CPU].
> > + */
> > + cpu = get_cpu();
> >
> > And need an smp_mb() here, again for non-x86 CPUs.
>
> The atomic_dec is already a barrier.

Sorry, I was confused. atomic_dec is not a barrier of course.
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