Messages in this thread | | | Date | Wed, 19 Jul 2017 07:51:30 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods |
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On Wed, Jul 19, 2017 at 03:43:07PM +0200, Frederic Weisbecker wrote: > On Wed, Jul 12, 2017 at 08:56:51AM -0700, Paul E. McKenney wrote: > > On Wed, Jul 12, 2017 at 01:54:51PM +0200, Peter Zijlstra wrote: > > > On Tue, Jul 11, 2017 at 11:09:31AM -0700, Paul E. McKenney wrote: > > > > On Tue, Jul 11, 2017 at 06:34:22PM +0200, Peter Zijlstra wrote: > > > > > > > > But I think we can at the very least do this; it only gets called from > > > > > kernel/sched/idle.c and both callsites have IRQs explicitly disabled by > > > > > that point. > > > > > > > > > > > > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > > > > index 51d4c3acf32d..dccf2dc8155a 100644 > > > > > --- a/kernel/rcu/tree.c > > > > > +++ b/kernel/rcu/tree.c > > > > > @@ -843,13 +843,8 @@ static void rcu_eqs_enter(bool user) > > > > > */ > > > > > void rcu_idle_enter(void) > > > > > { > > > > > - unsigned long flags; > > > > > - > > > > > - local_irq_save(flags); > > > > > > > > With this addition, I am all for it: > > > > > > > > RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_idle_enter() invoked with irqs enabled!!!"); > > > > > > > > If you are OK with this addition, may I please have your Signed-off-by? > > > > > > Sure, > > > > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > > > 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. > > > > Fair enough? > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit 95f3e587ce6388028a51f0c852800fca944e7032 > > Author: Peter Zijlstra (Intel) <peterz@infradead.org> > > Date: Wed Jul 12 07:59:54 2017 -0700 > > > > rcu: Make rcu_idle_enter() rely on callers disabling irqs > > > > All callers to rcu_idle_enter() have irqs disabled, so there is no > > point in rcu_idle_enter disabling them again. This commit therefore > > replaces the irq disabling with a RCU_LOCKDEP_WARN(). > > > > Signed-off-by: Peter Zijlstra (Intel) <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 6de6b1c5ee53..c78b076653ce 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -840,11 +840,8 @@ static void rcu_eqs_enter(bool user) > > */ > > void rcu_idle_enter(void) > > { > > - unsigned long flags; > > - > > - local_irq_save(flags); > > + RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_idle_enter() invoked with irqs enabled!!!"); > > Nice! I really need to make that LOCKDEP_ASSERT_IRQS_DISABLED() patchset because there > are many places where either we have WARN_ON_ONCE(!irqs_disabled()) or we need it but we were too > shy to do it for performance reason.
If you create it, let me know, I could switch to it.
Thanx, Paul
> > rcu_eqs_enter(false); > > - local_irq_restore(flags); > > } > > EXPORT_SYMBOL_GPL(rcu_idle_enter); > > > > >
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