From 7f11536abb58e277f1c29eef8b5e40b3c11beee5 Mon Sep 17 00:00:00 2001
From: Nicholas Mc Guire <der.herr@hofr.at>
Date: Fri, 17 Jan 2014 20:41:58 +0100
Subject: use local spin_locks in local_lock

Drop recursive call to migrate_disabel/enable for local_*lock* api
reported by Steven Rostedt.

local_lock will call migrate_disable via get_local_var - call tree is

get_locked_var
 `-> local_lock(lvar)
       `-> __local_lock(&get_local_var(lvar));
                          `--> # define get_local_var(var) (*({
                                    migrate_disable();
                                    &__get_cpu_var(var); }))       \

thus there should be no need to call migrate_disable/enable recursively in
spin_try/lock/unlock. This patch addes a spin_trylock_local and replaces
the migration disabling calls by the local calls.

This patch is incomplete as it does not yet cover the _irq/_irqsave variants
by local locks. This patch requires the API cleanup in kernel/softirq.c or
it would break softirq_lock/unlock with respect to migration.

Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

diff --git a/include/linux/locallock.h b/include/linux/locallock.h
index e7bd8be..eb338ce 100644
--- a/include/linux/locallock.h
+++ b/include/linux/locallock.h
@@ -36,10 +36,20 @@ struct local_irq_lock {
 			spin_lock_init(&per_cpu(lvar, __cpu).lock);	\
 	} while (0)
 
+/*
+ * spin_lock|trylock|unlock_local flavour that does not migrate disable
+ * used for __local_lock|trylock|unlock where get_local_var/put_local_var
+ * already takes care of the migrate_disable/enable
+ * for CONFIG_PREEMPT_BASE map to the normal spin_* calls.
+ */
+# define spin_lock_local(lock)			spin_lock(lock)
+# define spin_trylock_local(lock)		spin_trylock(lock)
+# define spin_unlock_local(lock)		spin_unlock(lock)
+
 static inline void __local_lock(struct local_irq_lock *lv)
 {
 	if (lv->owner != current) {
-		spin_lock(&lv->lock);
+		spin_lock_local(&lv->lock);
 		LL_WARN(lv->owner);
 		LL_WARN(lv->nestcnt);
 		lv->owner = current;
@@ -52,7 +62,7 @@ static inline void __local_lock(struct local_irq_lock *lv)
 
 static inline int __local_trylock(struct local_irq_lock *lv)
 {
-	if (lv->owner != current && spin_trylock(&lv->lock)) {
+	if (lv->owner != current && spin_trylock_local(&lv->lock)) {
 		LL_WARN(lv->owner);
 		LL_WARN(lv->nestcnt);
 		lv->owner = current;
@@ -79,7 +89,7 @@ static inline void __local_unlock(struct local_irq_lock *lv)
 		return;
 
 	lv->owner = NULL;
-	spin_unlock(&lv->lock);
+	spin_unlock_local(&lv->lock);
 }
 
 #define local_unlock(lvar)					\
@@ -211,7 +221,7 @@ static inline int __local_unlock_irqrestore(struct local_irq_lock *lv,
 		&__get_cpu_var(var);					\
 	}))
 
-#define put_locked_var(lvar, var)		local_unlock(lvar)
+#define put_locked_var(lvar, var)	local_unlock(lvar);
 
 #define local_lock_cpu(lvar)						\
 	({								\
-- 
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