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Date: Fri, 9 Aug 2013 18:20:59 +0200 From: Frederic Weisbecker <fweisbec@...il.com> To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com, akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com, darren@...art.com, sbw@....edu Subject: Re: [PATCH RFC nohz_full 6/7] nohz_full: Add full-system-idle state machine On Fri, Jul 26, 2013 at 04:19:23PM -0700, Paul E. McKenney wrote: > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > index 3edae39..ff84bed 100644 > --- a/kernel/rcutree_plugin.h > +++ b/kernel/rcutree_plugin.h > @@ -28,7 +28,7 @@ > #include <linux/gfp.h> > #include <linux/oom.h> > #include <linux/smpboot.h> > -#include <linux/tick.h> > +#include "time/tick-internal.h" > > #define RCU_KTHREAD_PRIO 1 > > @@ -2395,12 +2395,12 @@ static void rcu_kick_nohz_cpu(int cpu) > * most active flavor of RCU. > */ > #ifdef CONFIG_PREEMPT_RCU > -static struct rcu_state __maybe_unused *rcu_sysidle_state = &rcu_preempt_state; > +static struct rcu_state *rcu_sysidle_state = &rcu_preempt_state; > #else /* #ifdef CONFIG_PREEMPT_RCU */ > -static struct rcu_state __maybe_unused *rcu_sysidle_state = &rcu_sched_state; > +static struct rcu_state *rcu_sysidle_state = &rcu_sched_state; > #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ Ah you fixed it here. Ok :) > > -static int __maybe_unused full_sysidle_state; /* Current system-idle state. */ > +static int full_sysidle_state; /* Current system-idle state. */ > #define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ > #define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ > #define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ [...] > +/* > + * Check to see if the system is fully idle, other than the timekeeping CPU. > + * The caller must have disabled interrupts. > + */ > +bool rcu_sys_is_idle(void) > +{ > + static struct rcu_sysidle_head rsh; > + int rss = ACCESS_ONCE(full_sysidle_state); > + > + if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu)) > + return false; > + > + /* Handle small-system case by doing a full scan of CPUs. */ > + if (nr_cpu_ids <= RCU_SYSIDLE_SMALL) { I don't understand how the nr_cpu_ids > RCU_SYSIDLE_SMALL is handled. There don't seem to be other calls of rcu_sysidle_check_cpu() than for small systems. -- 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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