On Tue, 3 Sep 2013 22:01:15 -0400
Steven Rostedt <rost...@goodmis.org> wrote:
> 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.
>
Here's the changes against this one:
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index cdcf187..9e6902a 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -569,14 +569,14 @@ void ftrace_unsafe_rcu_checker_disable(void)
{
atomic_inc(&ftrace_unsafe_rcu_disabled);
/* Make sure the update is seen immediately */
- smp_wmb();
+ smp_mb__after_atomic_inc();
}
void ftrace_unsafe_rcu_checker_enable(void)
{
atomic_dec(&ftrace_unsafe_rcu_disabled);
/* Make sure the update is seen immediately */
- smp_wmb();
+ smp_mb__after_atomic_dec();
}
static void
Which is nice, because the smp_mb() are now in the really slow path.
-- Steve
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