linux-kernel - [PATCH v2 2/4] jump_label: Split out code under the hotplug lock

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Message-Id: <20170801080257.5056-3-marc.zyngier@arm.com>
Date:   Tue,  1 Aug 2017 09:02:55 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v2 2/4] jump_label: Split out code under the hotplug lock

In order to later introduce an "already locked" version of some
of the static key funcions, let's split the code into the core stuff
(the *_cpuslocked functions) and the usual helpers, which now
take/release the hotplug lock and call into the _cpuslocked
versions.

Signed-off-by: Marc Zyngier <marc.zyngier@....com>
---
 kernel/jump_label.c | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index f11b10091100..0ab8b35daa54 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -101,11 +101,10 @@ void static_key_disable(struct static_key *key)
 }
 EXPORT_SYMBOL_GPL(static_key_disable);
 
-void static_key_slow_inc(struct static_key *key)
+static void static_key_slow_inc_cpuslocked(struct static_key *key)
 {
 	int v, v1;
 
-	cpus_read_lock();
 	STATIC_KEY_CHECK_USE();
 
 	/*
@@ -122,10 +121,8 @@ 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)) {
-			cpus_read_unlock();
+		if (likely(v1 == v))
 			return;
-		}
 	}
 
 	jump_label_lock();
@@ -137,14 +134,20 @@ void static_key_slow_inc(struct static_key *key)
 		atomic_inc(&key->enabled);
 	}
 	jump_label_unlock();
+}
+
+void static_key_slow_inc(struct static_key *key)
+{
+	cpus_read_lock();
+	static_key_slow_inc_cpuslocked(key);
 	cpus_read_unlock();
 }
 EXPORT_SYMBOL_GPL(static_key_slow_inc);
 
-static void __static_key_slow_dec(struct static_key *key,
-		unsigned long rate_limit, struct delayed_work *work)
+static void static_key_slow_dec_cpuslocked(struct static_key *key,
+					   unsigned long rate_limit,
+					   struct delayed_work *work)
 {
-	cpus_read_lock();
 	/*
 	 * The negative count check is valid even when a negative
 	 * key->enabled is in use by static_key_slow_inc(); a
@@ -155,7 +158,6 @@ static void __static_key_slow_dec(struct static_key *key,
 	if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
 		WARN(atomic_read(&key->enabled) < 0,
 		     "jump label: negative count!\n");
-		cpus_read_unlock();
 		return;
 	}
 
@@ -166,6 +168,14 @@ static void __static_key_slow_dec(struct static_key *key,
 		jump_label_update(key);
 	}
 	jump_label_unlock();
+}
+
+static void __static_key_slow_dec(struct static_key *key,
+				  unsigned long rate_limit,
+				  struct delayed_work *work)
+{
+	cpus_read_lock();
+	static_key_slow_dec_cpuslocked(key, rate_limit, work);
 	cpus_read_unlock();
 }
 
-- 
2.11.0