linux-kernel - [tip:locking/core] jump_label: Move CPU hotplug locking

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Date:   Thu, 10 Aug 2017 05:14:01 -0700
From:   tip-bot for Marc Zyngier <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, hpa@...or.com, tglx@...utronix.de,
        marc.zyngier@....com, torvalds@...ux-foundation.org,
        mingo@...nel.org, peterz@...radead.org, leo.yan@...aro.org
Subject: [tip:locking/core] jump_label: Move CPU hotplug locking

Commit-ID:  b70cecf4b6b72a9977576ab32cca0e24f286f517
Gitweb:     http://git.kernel.org/tip/b70cecf4b6b72a9977576ab32cca0e24f286f517
Author:     Marc Zyngier <marc.zyngier@....com>
AuthorDate: Tue, 1 Aug 2017 09:02:54 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Aug 2017 12:28:58 +0200

jump_label: Move CPU hotplug locking

As we're about to rework the locking, let's move the taking and
release of the CPU hotplug lock to locations that will make its
reworking completely obvious.

Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Leo Yan <leo.yan@...aro.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-arm-kernel@...ts.infradead.org
Link: http://lkml.kernel.org/r/20170801080257.5056-2-marc.zyngier@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/jump_label.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index f2ea678..161301f 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -83,6 +83,7 @@ void static_key_slow_inc(struct static_key *key)
 {
 	int v, v1;
 
+	cpus_read_lock();
 	STATIC_KEY_CHECK_USE();
 
 	/*
@@ -99,11 +100,12 @@ void static_key_slow_inc(struct static_key *key)
 	 */
 	for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 		v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
-		if (likely(v1 == v))
+		if (likely(v1 == v)) {
+			cpus_read_unlock();
 			return;
+		}
 	}
 
-	cpus_read_lock();
 	jump_label_lock();
 	if (atomic_read(&key->enabled) == 0) {
 		atomic_set(&key->enabled, -1);