1 files changed, 30 insertions, 16 deletions

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 2cb7531e7d7a..4d3bccabbea5 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -18,6 +18,7 @@
 #include <linux/atomic.h>
 #include <asm/processor.h>
 #include <linux/osq_lock.h>
+#include <linux/debug_locks.h>
 
 /*
  * Simple, straightforward mutexes with strict semantics:
@@ -48,16 +49,12 @@
  *   locks and tasks (and only those tasks)
  */
 struct mutex {
-        /* 1: unlocked, 0: locked, negative: locked, possible waiters */
-        atomic_t                count;
+        atomic_long_t           owner;
         spinlock_t              wait_lock;
-        struct list_head        wait_list;
-#if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_MUTEX_SPIN_ON_OWNER)
-        struct task_struct      *owner;
-#endif
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
         struct optimistic_spin_queue osq; /* Spinner MCS lock */
 #endif
+        struct list_head        wait_list;
 #ifdef CONFIG_DEBUG_MUTEXES
         void                    *magic;
 #endif
@@ -66,6 +63,11 @@ struct mutex {
 #endif
 };
 
+static inline struct task_struct *__mutex_owner(struct mutex *lock)
+{
+        return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x03);
+}
+
 /*
  * This is the control structure for tasks blocked on mutex,
  * which resides on the blocked task's kernel stack:
@@ -79,9 +81,20 @@ struct mutex_waiter {
 };
 
 #ifdef CONFIG_DEBUG_MUTEXES
-# include <linux/mutex-debug.h>
+
+#define __DEBUG_MUTEX_INITIALIZER(lockname)                             \
+        , .magic = &lockname
+
+extern void mutex_destroy(struct mutex *lock);
+
 #else
+
 # define __DEBUG_MUTEX_INITIALIZER(lockname)
+
+static inline void mutex_destroy(struct mutex *lock) {}
+
+#endif
+
 /**
  * mutex_init - initialize the mutex
  * @mutex: the mutex to be initialized
@@ -90,14 +103,12 @@ struct mutex_waiter {
  *
  * It is not allowed to initialize an already locked mutex.
  */
-# define mutex_init(mutex) \
-do {                                                    \
-        static struct lock_class_key __key;             \
-                                                        \
-        __mutex_init((mutex), #mutex, &__key);          \
+#define mutex_init(mutex)                                               \
+do {                                                                    \
+        static struct lock_class_key __key;                             \
+                                                                        \
+        __mutex_init((mutex), #mutex, &__key);                          \
 } while (0)
-static inline void mutex_destroy(struct mutex *lock) {}
-#endif
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
@@ -107,7 +118,7 @@ static inline void mutex_destroy(struct mutex *lock) {}
 #endif
 
 #define __MUTEX_INITIALIZER(lockname) \
-                { .count = ATOMIC_INIT(1) \
+                { .owner = ATOMIC_LONG_INIT(0) \
                 , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
                 , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
                 __DEBUG_MUTEX_INITIALIZER(lockname) \
@@ -127,7 +138,10 @@ extern void __mutex_init(struct mutex *lock, const char *name,
  */
 static inline int mutex_is_locked(struct mutex *lock)
 {
-        return atomic_read(&lock->count) != 1;
+        /*
+         * XXX think about spin_is_locked
+         */
+        return __mutex_owner(lock) != NULL;
 }
 
 /*