linux-kernel - Re: [PATCH 21/27] nohz: Only stop the tick on RCU nocb CPUs

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Date:	Wed, 02 Jan 2013 17:47:33 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 21/27] nohz: Only stop the tick on RCU nocb CPUs

Hi Frederic,

On Sat, 29 Dec 2012 17:43:00 +0100, Frederic Weisbecker wrote:
> On a full dynticks CPU, we want the RCU callbacks to be
> offlined to another CPU, otherwise we need to keep
> the tick to wait for the grace period completion.
>
> Ensure the full dynticks CPU is also an rcu_nocb one.
[snip]
> -static bool is_nocb_cpu(int cpu)
> -{
> -	return false;
> -}
> -

You may want to add the following also to shut up the gcc:

      CC      kernel/rcutree.o
    In file included from /home/namhyung/project/linux/kernel/rcutree.c:58:0:
    /home/namhyung/project/linux/kernel/rcutree.h:539:13: warning: ‘is_nocb_cpu’ declared ‘static’ but never defined [-Wunused-function]


Thanks,
Namhyung


diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 4b69291b093d..fbbad931c36a 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -536,7 +536,6 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
 static void print_cpu_stall_info_end(void);
 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
 static void increment_cpu_stall_ticks(void);
-static bool is_nocb_cpu(int cpu);
 static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
                            bool lazy);
 static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
--
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