linux-kernel - Re: [RFC][PATCH 4/9] idle: Fix rcu_idle

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Message-ID: <YpXhB4yjdNKOe6Np@hirez.programming.kicks-ass.net>
Date:   Tue, 31 May 2022 11:33:59 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Gautham R. Shenoy" <gautham.shenoy@....com>
Cc:     frederic@...nel.org, paulmck@...nel.org, rjw@...ysocki.net,
        x86@...nel.org, linux-kernel@...r.kernel.org, jpoimboe@...nel.org
Subject: Re: [RFC][PATCH 4/9] idle: Fix rcu_idle_*() usage

On Mon, May 23, 2022 at 03:16:11PM +0530, Gautham R. Shenoy wrote:
> On Thu, May 19, 2022 at 11:27:54PM +0200, Peter Zijlstra wrote:
> > The whole disable-RCU, enable-IRQS dance is very intricate since
> > changing IRQ state is traced, which depends on RCU.
> > 
> > Add two helpers for the cpuidle case that mirror the entry code.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > ---
> 
> [...]
> >  
> > --- a/drivers/cpuidle/cpuidle.c
> > +++ b/drivers/cpuidle/cpuidle.c
> > @@ -13,6 +13,7 @@
> >  #include <linux/mutex.h>
> >  #include <linux/sched.h>
> >  #include <linux/sched/clock.h>
> > +#include <linux/sched/idle.h>
> >  #include <linux/notifier.h>
> >  #include <linux/pm_qos.h>
> >  #include <linux/cpu.h>
> > @@ -150,12 +151,12 @@ static void enter_s2idle_proper(struct c
> >  	 */
> >  	stop_critical_timings();
> >  	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
> > -		rcu_idle_enter();
> > +		cpuidle_rcu_enter();
> >  	target_state->enter_s2idle(dev, drv, index);
> >  	if (WARN_ON_ONCE(!irqs_disabled()))
> > -		local_irq_disable();
> > +		raw_local_irq_disable();
> >  	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
> > -		rcu_idle_exit();
> > +		cpuidle_rcu_enter();
> 
> Shouldn't this be cpuidle_rcu_exit() ?

Yes, very much so... soon I should buy a new supply of brown paper bags
:-)