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From:   Yury Norov <yury.norov@gmail.com>
To:     Yury Norov <yury.norov@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Andrew Morton <akpm@linux-foundation.org>,
        =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= <mirq-linux@rere.qmqm.pl>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        David Laight <David.Laight@aculab.com>,
        Joe Perches <joe@perches.com>, Dennis Zhou <dennis@kernel.org>,
        Emil Renner Berthing <kernel@esmil.dk>,
        Nicholas Piggin <npiggin@gmail.com>,
        Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>,
        Alexey Klimov <aklimov@redhat.com>,
        linux-kernel@vger.kernel.org,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Josh Triplett <josh@joshtriplett.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Joel Fernandes <joel@joelfernandes.org>, rcu@vger.kernel.org
Subject: [PATCH 22/54] rcu: replace cpumask_weight with cpumask_empty where appropriate
Date:   Sun, 23 Jan 2022 10:38:53 -0800
Message-Id: <20220123183925.1052919-23-yury.norov@gmail.com>
In-Reply-To: <20220123183925.1052919-1-yury.norov@gmail.com>
References: <20220123183925.1052919-1-yury.norov@gmail.com>
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In some places, RCU code calls cpumask_weight() to check if any bit of a
given cpumask is set. We can do it more efficiently with cpumask_empty()
because cpumask_empty() stops traversing the cpumask as soon as it finds
first set bit, while cpumask_weight() counts all bits unconditionally.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 kernel/rcu/tree_nocb.h   | 4 ++--
 kernel/rcu/tree_plugin.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index eeafb546a7a0..f83c7b1d6110 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1169,7 +1169,7 @@ void __init rcu_init_nohz(void)
 	struct rcu_data *rdp;
 
 #if defined(CONFIG_NO_HZ_FULL)
-	if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask))
+	if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask))
 		need_rcu_nocb_mask = true;
 #endif /* #if defined(CONFIG_NO_HZ_FULL) */
 
@@ -1348,7 +1348,7 @@ static void __init rcu_organize_nocb_kthreads(void)
  */
 void rcu_bind_current_to_nocb(void)
 {
-	if (cpumask_available(rcu_nocb_mask) && cpumask_weight(rcu_nocb_mask))
+	if (cpumask_available(rcu_nocb_mask) && !cpumask_empty(rcu_nocb_mask))
 		WARN_ON(sched_setaffinity(current->pid, rcu_nocb_mask));
 }
 EXPORT_SYMBOL_GPL(rcu_bind_current_to_nocb);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c5b45c2f68a1..0dc0c8d6717c 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1215,7 +1215,7 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
 		    cpu != outgoingcpu)
 			cpumask_set_cpu(cpu, cm);
 	cpumask_and(cm, cm, housekeeping_cpumask(HK_FLAG_RCU));
-	if (cpumask_weight(cm) == 0)
+	if (cpumask_empty(cm))
 		cpumask_copy(cm, housekeeping_cpumask(HK_FLAG_RCU));
 	set_cpus_allowed_ptr(t, cm);
 	free_cpumask_var(cm);
-- 
2.30.2