linux-kernel - [PATCH] rcu: Clean up rcu_init_nohz() by removing unnecessary statements

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Date:   Wed, 28 Feb 2018 18:04:55 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     jiangshanlai@...il.com, paulmck@...ux.vnet.ibm.com,
        josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com
Cc:     linux-kernel@...r.kernel.org, kernel-team@....com
Subject: [PATCH] rcu: Clean up rcu_init_nohz() by removing unnecessary statements

Since the commit 44c65ff2e3b0(rcu: Eliminate NOCBs CPU-state Kconfig
options) made nocb-cpus identified only through the rcu_nocbs= boot
parameter, we don't have to care NOCBs CPU-state Kconfig options
anymore, which means now we can just rely on rcu_nocb_mask to
decide whether going ahead in rcu_init_nohz().

Remove the deprecated code.

Signed-off-by: Byungchul Park <byungchul.park@....com>
---
 kernel/rcu/tree_plugin.h | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index b0d7f9b..510a6af 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2313,22 +2313,14 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp)
 void __init rcu_init_nohz(void)
 {
 	int cpu;
-	bool need_rcu_nocb_mask = true;
 	struct rcu_state *rsp;
 
-#if defined(CONFIG_NO_HZ_FULL)
-	if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask))
-		need_rcu_nocb_mask = true;
-#endif /* #if defined(CONFIG_NO_HZ_FULL) */
-
-	if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) {
+	if (!cpumask_available(rcu_nocb_mask)) {
 		if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
 			pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
 			return;
 		}
 	}
-	if (!cpumask_available(rcu_nocb_mask))
-		return;
 
 #if defined(CONFIG_NO_HZ_FULL)
 	if (tick_nohz_full_running)
-- 
1.9.1