linux-kernel - Re: [GIT PULL rcu/next] RCU commits for 3.3

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Date:	Wed, 14 Dec 2011 17:41:13 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"josh@...htriplett.org" <josh@...htriplett.org>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL rcu/next] RCU commits for 3.3

On Wed, Dec 14, 2011 at 05:35:22PM -0800, Suresh Siddha wrote:
> On Wed, 2011-12-14 at 09:47 -0800, Frederic Weisbecker wrote:
> > I don't know how you plan to fix the conflict, by redoing the merge or by
> > applying a patch on tip/master.
> > 
> > In any case, here is a patch you can use. Feel free to apply it as is
> > or to just refer to its diff to redo the merge:
> > 
> > (Outrageously only compile tested)
> > 
> > ---
> > From: Frederic Weisbecker <fweisbec@...il.com>
> > Date: Wed, 14 Dec 2011 18:36:00 +0100
> > Subject: [PATCH] sched: Only update the CPU idleness in the domain
> >  hierarchy from idle loop entry
> > 
> > We don't need to inform the sched domain hierarchy about the
> > CPU idleness everytime we call tick_nohz_stop_sched_tick() as this
> > includes both idle loop entry and idle interrupt exit.
> > 
> > Doing it once from the idle loop entry is enough, call
> > set_cpu_sd_state_idle() only from tick_nohz_idle_enter() instead
> > to fix this.
> > 
> > Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> > Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > Cc: Suresh Siddha <suresh.b.siddha@...el.com>
> > Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> 
> Acked-by: Suresh Siddha <suresh.b.siddha@...el.com>

Tested-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> > ---
> >  kernel/time/tick-sched.c |   16 ++++++++--------
> >  1 files changed, 8 insertions(+), 8 deletions(-)
> > 
> > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> > index 1f6dc515..696c997 100644
> > --- a/kernel/time/tick-sched.c
> > +++ b/kernel/time/tick-sched.c
> > @@ -289,14 +289,6 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts)
> >         now = tick_nohz_start_idle(cpu, ts);
> > 
> >         /*
> > -        * Update the idle state in the scheduler domain hierarchy
> > -        * when tick_nohz_stop_sched_tick() is called from the idle loop.
> > -        * State will be updated to busy during the first busy tick after
> > -        * exiting idle.
> > -        */
> > -       set_cpu_sd_state_idle();
> > -
> > -       /*
> >          * If this cpu is offline and it is the one which updates
> >          * jiffies, then give up the assignment and let it be taken by
> >          * the cpu which runs the tick timer next. If we don't drop
> > @@ -483,6 +475,14 @@ void tick_nohz_idle_enter(void)
> >          * update of the idle time accounting in tick_nohz_start_idle().
> >          */
> >         ts->inidle = 1;
> > +
> > +       /*
> > +        * Update the idle state in the scheduler domain hierarchy
> > +        * when tick_nohz_idle_enter() is called from the idle loop.
> > +        * State will be updated to busy during the first busy tick after
> > +        * exiting idle.
> > +        */
> > +       set_cpu_sd_state_idle();
> >         tick_nohz_stop_sched_tick(ts);
> > 
> >         local_irq_enable();
> > --
> > 1.7.5.4
> > 
> > 
> 
> 

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