Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm…

…/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:

 - improve rwsem scalability

 - add uninitialized rwsem debugging check

 - reduce lockdep's stacktrace memory usage and add diagnostics

 - misc cleanups, code consolidation and constification

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  mutex: Fix up mutex_waiter usage
  locking/mutex: Use mutex flags macro instead of hard code
  locking/mutex: Make __mutex_owner static to mutex.c
  locking/qspinlock,x86: Clarify virt_spin_lock_key
  locking/rwsem: Check for operations on an uninitialized rwsem
  locking/rwsem: Make handoff writer optimistically spin on owner
  locking/lockdep: Report more stack trace statistics
  locking/lockdep: Reduce space occupied by stack traces
  stacktrace: Constify 'entries' arguments
  locking/lockdep: Make it clear that what lock_class::key points at is not modified

arch/x86/include/asm/qspinlock.h

@@ -63,10 +63,25 @@ static inline bool vcpu_is_preempted(long cpu)
 #endif
 
 #ifdef CONFIG_PARAVIRT
+/*
+ * virt_spin_lock_key - enables (by default) the virt_spin_lock() hijack.
+ *
+ * Native (and PV wanting native due to vCPU pinning) should disable this key.
+ * It is done in this backwards fashion to only have a single direction change,
+ * which removes ordering between native_pv_spin_init() and HV setup.
+ */
 DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key);
 
 void native_pv_lock_init(void) __init;
 
+/*
+ * Shortcut for the queued_spin_lock_slowpath() function that allows
+ * virt to hijack it.
+ *
+ * Returns:
+ *   true - lock has been negotiated, all done;
+ *   false - queued_spin_lock_slowpath() will do its thing.
+ */
 #define virt_spin_lock virt_spin_lock
 static inline bool virt_spin_lock(struct qspinlock *lock)
 {

include/linux/lockdep.h

@@ -66,10 +66,7 @@ struct lock_class_key {
 
 extern struct lock_class_key __lockdep_no_validate__;
 
-struct lock_trace {
-	unsigned int		nr_entries;
-	unsigned int		offset;
-};
+struct lock_trace;
 
 #define LOCKSTAT_POINTS		4
 
@@ -97,15 +94,15 @@ struct lock_class {
 	 */
 	struct list_head		locks_after, locks_before;
 
-	struct lockdep_subclass_key	*key;
+	const struct lockdep_subclass_key *key;
 	unsigned int			subclass;
 	unsigned int			dep_gen_id;
 
 	/*
 	 * IRQ/softirq usage tracking bits:
 	 */
 	unsigned long			usage_mask;
-	struct lock_trace		usage_traces[XXX_LOCK_USAGE_STATES];
+	const struct lock_trace		*usage_traces[XXX_LOCK_USAGE_STATES];
 
 	/*
 	 * Generation counter, when doing certain classes of graph walking,
@@ -193,7 +190,7 @@ struct lock_list {
 	struct list_head		entry;
 	struct lock_class		*class;
 	struct lock_class		*links_to;
-	struct lock_trace		trace;
+	const struct lock_trace		*trace;
 	int				distance;
 
 	/*

include/linux/mutex.h

@@ -65,16 +65,6 @@ struct mutex {
 #endif
 };
 
-/*
- * 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:
@@ -144,10 +134,7 @@ extern void __mutex_init(struct mutex *lock, const char *name,
  *
  * 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 bool mutex_is_locked(struct mutex *lock);
 
 /*
  * See kernel/locking/mutex.c for detailed documentation of these APIs.
@@ -220,13 +207,7 @@ enum mutex_trylock_recursive_enum {
  *  - 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);
-}
+extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
+mutex_trylock_recursive(struct mutex *lock);
 
 #endif /* __LINUX_MUTEX_H */

include/linux/rwsem.h

@@ -45,6 +45,9 @@ struct rw_semaphore {
 #endif
 	raw_spinlock_t wait_lock;
 	struct list_head wait_list;
+#ifdef CONFIG_DEBUG_RWSEMS
+	void *magic;
+#endif
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	struct lockdep_map	dep_map;
 #endif
@@ -73,6 +76,12 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
 # define __RWSEM_DEP_MAP_INIT(lockname)
 #endif
 
+#ifdef CONFIG_DEBUG_RWSEMS
+# define __DEBUG_RWSEM_INITIALIZER(lockname) , .magic = &lockname
+#else
+# define __DEBUG_RWSEM_INITIALIZER(lockname)
+#endif
+
 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
 #define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED
 #else
@@ -85,6 +94,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
 	  .wait_list = LIST_HEAD_INIT((name).wait_list),	\
 	  .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock)	\
 	  __RWSEM_OPT_INIT(name)				\
+	  __DEBUG_RWSEM_INITIALIZER(name)			\
 	  __RWSEM_DEP_MAP_INIT(name) }
 
 #define DECLARE_RWSEM(name) \

include/linux/stacktrace.h

@@ -9,9 +9,9 @@ struct task_struct;
 struct pt_regs;
 
 #ifdef CONFIG_STACKTRACE
-void stack_trace_print(unsigned long *trace, unsigned int nr_entries,
+void stack_trace_print(const unsigned long *trace, unsigned int nr_entries,
 		       int spaces);
-int stack_trace_snprint(char *buf, size_t size, unsigned long *entries,
+int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
 			unsigned int nr_entries, int spaces);
 unsigned int stack_trace_save(unsigned long *store, unsigned int size,
 			      unsigned int skipnr);