On Tue, 3 Sep 2013 18:24:04 -0700
"Paul E. McKenney" <paul...@linux.vnet.ibm.com> wrote:
> > static DEFINE_PER_CPU(unsigned long, ftrace_rcu_func);
> > @@ -588,15 +593,14 @@ static void
> > ftrace_unsafe_callback(unsigned long ip, unsigned long parent_ip,
> > struct ftrace_ops *op, struct pt_regs *pt_regs)
> > {
> > - int bit;
> > -
> > + /* Make sure we see disabled or not first */
> > + smp_rmb();
>
> smp_mb__before_atomic_inc()?
>
Ah, but this is before an atomic_read(), and not an atomic_inc(), thus
the normal smp_rmb() is still required.
-- Steve
> > if (atomic_read(&ftrace_unsafe_rcu_disabled))
> > return;
> >
> > preempt_disable_notrace();
> >
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