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Date: Sun, 7 Sep 2008 10:25:36 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Manfred Spraul <manfred@...orfullife.com> Cc: linux-kernel@...r.kernel.org, cl@...ux-foundation.org, mingo@...e.hu, akpm@...ux-foundation.org, dipankar@...ibm.com, josht@...ux.vnet.ibm.com, schamp@....com, niv@...ibm.com, dvhltc@...ibm.com, ego@...ibm.com, laijs@...fujitsu.com, rostedt@...dmis.org, peterz@...radead.org, penberg@...helsinki.fi, andi@...stfloor.org Subject: Re: [PATCH, RFC] v4 scalable classic RCU implementation On Sat, Sep 06, 2008 at 06:37:38PM +0200, Manfred Spraul wrote: > Hi Paul, > > Paul E. McKenney wrote: >> o The rcu_pending() and rcu_needs_cpu() primitives are now >> much more aggressive about permitting CPUs to enter dynticks >> idle mode. Only CPUs that have RCU callbacks are kept out >> of dynticks idle mode. >> > > I've noticed that right now rcu_enter_nohz() can be nested within > rcu_irq_enter(): > irq_exit() first calls tick_nohz_stop_sched_tick(), then rcu_irq_exit(). > And tick_nohz_stop_sched_tick() can switch into nohz mode. > > Is that intentional? Does rcupreempt support that? It broke my rcustate > code on x86-64. > > I would prefer if something like the attached patch is applied. What do you > think? > Do you need the patch as well? Good question -- when I tried splitting irqs from NMIs, things broke badly, and this might well explain it. Thank you very much for the hint!!! Thanx, Paul > -- > Manfred > diff --git a/kernel/softirq.c b/kernel/softirq.c > index ba20a90..cca5a83 100644 > --- a/kernel/softirq.c > +++ b/kernel/softirq.c > @@ -284,10 +284,10 @@ void irq_exit(void) > invoke_softirq(); > > #ifdef CONFIG_NO_HZ > + rcu_irq_exit(0); > /* Make sure that timer wheel updates are propagated */ > if (!in_interrupt() && idle_cpu(smp_processor_id()) && !need_resched()) > tick_nohz_stop_sched_tick(0); > - rcu_irq_exit(0); > #endif > preempt_enable_no_resched(); > } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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