linux-kernel - [PATCH 1/2 v2] locking/mutex: Make __mutex

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Message-Id: <1564501794-11379-1-git-send-email-mojha@codeaurora.org>
Date:   Tue, 30 Jul 2019 21:19:53 +0530
From:   Mukesh Ojha <mojha@...eaurora.org>
To:     peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Mukesh Ojha <mojha@...eaurora.org>
Subject: [PATCH 1/2 v2] locking/mutex: Make __mutex_owner static to mutex.c

__mutex_owner() should only be used by the mutex api's.
So, put this restiction let's move the __mutex_owner()
function definition from linux/mutex.h to mutex.c file.

There exist functions that uses __mutex_owner() like
mutex_is_locked() and mutex_trylock_recursive(), So
to keep the thing intact move them as well and
export them.

Signed-off-by: Mukesh Ojha <mojha@...eaurora.org>
---
Changes in v2:
- On Peterz suggestion, moved __mutex_owner() to mutex.c to
  make it static to mutex.c.

- Exported mutex_is_owner() and mutex_trylock_recursive()
  to keep the existing thing intact as there are loadable
  modules which uses these functions.

 include/linux/mutex.h  | 44 +++-----------------------------------------
 kernel/locking/mutex.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 41 deletions(-)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index dcd03fe..841b47d 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -66,16 +66,6 @@ struct mutex {
 };
 
 /*
- * Internal helper function; C doesn't allow us to hide it :/
- *
- * DO NOT USE (outside of mutex code).
- */
-static inline struct task_struct *__mutex_owner(struct mutex *lock)
-{
-	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
-}
-
-/*
  * This is the control structure for tasks blocked on mutex,
  * which resides on the blocked task's kernel stack:
  */
@@ -138,17 +128,10 @@ static inline void mutex_destroy(struct mutex *lock) {}
 extern void __mutex_init(struct mutex *lock, const char *name,
 			 struct lock_class_key *key);
 
-/**
- * mutex_is_locked - is the mutex locked
- * @lock: the mutex to be queried
- *
- * Returns true if the mutex is locked, false if unlocked.
- */
-static inline bool mutex_is_locked(struct mutex *lock)
-{
-	return __mutex_owner(lock) != NULL;
-}
+extern inline bool mutex_is_locked(struct mutex *lock);
 
+extern inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
+mutex_trylock_recursive(struct mutex *lock);
 /*
  * See kernel/locking/mutex.c for detailed documentation of these APIs.
  * Also see Documentation/locking/mutex-design.rst.
@@ -208,25 +191,4 @@ enum mutex_trylock_recursive_enum {
 	MUTEX_TRYLOCK_RECURSIVE,
 };
 
-/**
- * mutex_trylock_recursive - trylock variant that allows recursive locking
- * @lock: mutex to be locked
- *
- * This function should not be used, _ever_. It is purely for hysterical GEM
- * raisins, and once those are gone this will be removed.
- *
- * Returns:
- *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
- *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
- *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
- */
-static inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
-mutex_trylock_recursive(struct mutex *lock)
-{
-	if (unlikely(__mutex_owner(lock) == current))
-		return MUTEX_TRYLOCK_RECURSIVE;
-
-	return mutex_trylock(lock);
-}
-
 #endif /* __LINUX_MUTEX_H */
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 5e06973..f73250a 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -65,6 +65,50 @@
 
 #define MUTEX_FLAGS		0x07
 
+/*
+ * Internal helper function; C doesn't allow us to hide it :/
+ *
+ * DO NOT USE (outside of mutex code).
+ */
+static inline struct task_struct *__mutex_owner(struct mutex *lock)
+{
+	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
+}
+
+/**
+ * mutex_is_locked - is the mutex locked
+ * @lock: the mutex to be queried
+ *
+ * Returns true if the mutex is locked, false if unlocked.
+ */
+inline bool mutex_is_locked(struct mutex *lock)
+{
+	return __mutex_owner(lock) != NULL;
+}
+EXPORT_SYMBOL(mutex_is_locked);
+
+/**
+ * mutex_trylock_recursive - trylock variant that allows recursive locking
+ * @lock: mutex to be locked
+ *
+ * This function should not be used, _ever_. It is purely for hysterical GEM
+ * raisins, and once those are gone this will be removed.
+ *
+ * Returns:
+ *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
+ *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
+ *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
+ */
+inline /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
+mutex_trylock_recursive(struct mutex *lock)
+{
+	if (unlikely(__mutex_owner(lock) == current))
+		return MUTEX_TRYLOCK_RECURSIVE;
+
+	return mutex_trylock(lock);
+}
+EXPORT_SYMBOL(mutex_trylock_recursive);
+
 static inline struct task_struct *__owner_task(unsigned long owner)
 {
 	return (struct task_struct *)(owner & ~MUTEX_FLAGS);
-- 
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