linux-kernel - [PATCH 2/2] rcu: Remove needless preemption disablement in rcu_all

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Date:   Tue,  6 Jul 2021 01:43:44 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Paul E . McKenney" <paulmck@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: [PATCH 2/2] rcu: Remove needless preemption disablement in rcu_all_qs()

The preemption is already disabled when we write rcu_data.rcu_urgent_qs.
We can use __this_cpu_write() directly, although that path is mostly
used when CONFIG_PREEMPT=n.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Neeraj Upadhyay <neeraju@...eaurora.org>
Cc: Joel Fernandes <joel@...lfernandes.org>
Cc: Uladzislau Rezki <urezki@...il.com>
Cc: Boqun Feng <boqun.feng@...il.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 27b74352cccf..38b3d01424d7 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -871,7 +871,7 @@ void rcu_all_qs(void)
 		preempt_enable();
 		return;
 	}
-	this_cpu_write(rcu_data.rcu_urgent_qs, false);
+	__this_cpu_write(rcu_data.rcu_urgent_qs, false);
 	if (unlikely(raw_cpu_read(rcu_data.rcu_need_heavy_qs))) {
 		local_irq_save(flags);
 		rcu_momentary_dyntick_idle();
-- 
2.25.1