linux-kernel - [PATCH tip/core/rcu 05/17] rcu: remove redundant ACCESS_ONCE() from tick_do_timer

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Date:	Mon,  7 Jul 2014 15:38:09 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com,
	edumazet@...gle.com, dvhart@...ux.intel.com, fweisbec@...il.com,
	oleg@...hat.com, sbw@....edu,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 05/17] rcu: remove redundant ACCESS_ONCE() from tick_do_timer_cpu

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

In kernels built with CONFIG_NO_HZ_FULL, tick_do_timer_cpu is constant
once boot completes.  Thus, there is no need to wrap it in ACCESS_ONCE()
in code that is built only when CONFIG_NO_HZ_FULL.  This commit therefore
removes the redundant ACCESS_ONCE().

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tree_plugin.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 02ac0fb186b8..5da9f9b3abc9 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2844,7 +2844,7 @@ static bool rcu_nohz_full_cpu(struct rcu_state *rsp)
 static void rcu_bind_gp_kthread(void)
 {
 #ifdef CONFIG_NO_HZ_FULL
-	int cpu = ACCESS_ONCE(tick_do_timer_cpu);
+	int cpu = tick_do_timer_cpu;
 
 	if (cpu < 0 || cpu >= nr_cpu_ids)
 		return;
-- 
1.8.1.5

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