linux-kernel - [tip:locking/core] jump_label: Split out code under the hotplug lock

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Date:   Thu, 10 Aug 2017 05:14:24 -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,
        torvalds@...ux-foundation.org, mingo@...nel.org,
        peterz@...radead.org, marc.zyngier@....com, tglx@...utronix.de,
        leo.yan@...aro.org
Subject: [tip:locking/core] jump_label: Split out code under the hotplug
 lock

Commit-ID:  8b7b412807053ab5f059ffae426a280e769a5bda
Gitweb:     http://git.kernel.org/tip/8b7b412807053ab5f059ffae426a280e769a5bda
Author:     Marc Zyngier <marc.zyngier@....com>
AuthorDate: Tue, 1 Aug 2017 09:02:55 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Aug 2017 12:28:58 +0200

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>
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/20170801080257.5056-3-marc.zyngier@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 161301f..cc6d815 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -79,11 +79,10 @@ int static_key_count(struct static_key *key)
 }
 EXPORT_SYMBOL_GPL(static_key_count);
 
-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();
 
 	/*
@@ -100,10 +99,8 @@ 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();
@@ -119,6 +116,12 @@ 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);
@@ -163,10 +166,10 @@ void static_key_disable(struct static_key *key)
 }
 EXPORT_SYMBOL_GPL(static_key_disable);
 
-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
@@ -177,7 +180,6 @@ 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;
 	}
 
@@ -188,6 +190,14 @@ 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();
 }