Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

Paul E. McKenney
2017-07-12T19:00:15Z

On Wed, Jul 12, 2017 at 11:53:06AM -0700, Paul E. McKenney wrote:
> On Wed, Jul 12, 2017 at 07:46:42PM +0200, Peter Zijlstra wrote:
> > On Wed, Jul 12, 2017 at 08:56:51AM -0700, Paul E. McKenney wrote:
> > > Very good, I have queued the patch below. I left out the removal of
> > > the export as I need to work out why the export was there. If it turns
> > > out not to be needed, I will remove the related ones as well.
> >
> > 'git grep rcu_idle_enter' shows no callers other than
> > kernel/sched/idle.c. Which seems a clear indication its not needed.
> >
> > You also have to ask yourself, do I want joe module author to ever call
> > this. To which I suspect the answer is: hell no ;-)
>
> The other question is "why did I do this in the first place".
>
> The only case where there will turn out to have been a still-valid reason
> is if I remove it without checking first. ;-)

And I have now checked. Please see below.

Thanx, Paul

------------------------------------------------------------------------

commit 31b2fd02abe5f036d7e83461bd19bbca3636d62e
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Wed Jul 12 11:55:21 2017 -0700

rcu: Remove exports from rcu_idle_exit() and rcu_idle_enter()

The rcu_idle_exit() and rcu_idle_enter() functions are exported because
they were originally used by RCU_NONIDLE(), which was intended to
be usable from modules. However, RCU_NONIDLE() now instead uses
rcu_irq_enter_irqson() and rcu_irq_exit_irqson(), which are not
exported, and there have been no complaints.

This commit therefore removes the exports from rcu_idle_exit() and
rcu_idle_enter().

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 0798d2585e87..860d1c147606 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -843,7 +843,6 @@ void rcu_idle_enter(void)
RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_idle_enter() invoked with irqs enabled!!!");
rcu_eqs_enter(false);
}
-EXPORT_SYMBOL_GPL(rcu_idle_enter);

#ifdef CONFIG_NO_HZ_FULL
/**
@@ -976,7 +975,6 @@ void rcu_idle_exit(void)
rcu_eqs_exit(false);
local_irq_restore(flags);
}
-EXPORT_SYMBOL_GPL(rcu_idle_exit);

#ifdef CONFIG_NO_HZ_FULL
/**