include/qemu/thread.h - third_party/qemu - Git at Google

 #ifndef QEMU_THREAD_H
 #define QEMU_THREAD_H

 #include "qemu/processor.h"
 #include "qemu/atomic.h"

 typedef struct QemuCond QemuCond;
 typedef struct QemuSemaphore QemuSemaphore;
 typedef struct QemuEvent QemuEvent;
 typedef struct QemuLockCnt QemuLockCnt;
 typedef struct QemuThread QemuThread;

 #ifdef _WIN32
 #include "qemu/thread-win32.h"
 #else
 #include "qemu/thread-posix.h"
 #endif

 /* include QSP header once QemuMutex, QemuCond etc. are defined */
 #include "qemu/qsp.h"

 #define QEMU_THREAD_JOINABLE 0
 #define QEMU_THREAD_DETACHED 1

 void qemu_mutex_init(QemuMutex *mutex);
 void qemu_mutex_destroy(QemuMutex *mutex);
 int qemu_mutex_trylock_impl(QemuMutex *mutex, const char *file, const int line);
 void qemu_mutex_lock_impl(QemuMutex *mutex, const char *file, const int line);
 void qemu_mutex_unlock_impl(QemuMutex *mutex, const char *file, const int line);

 typedef void (*QemuMutexLockFunc)(QemuMutex *m, const char *f, int l);
 typedef int (*QemuMutexTrylockFunc)(QemuMutex *m, const char *f, int l);
 typedef void (*QemuRecMutexLockFunc)(QemuRecMutex *m, const char *f, int l);
 typedef int (*QemuRecMutexTrylockFunc)(QemuRecMutex *m, const char *f, int l);
 typedef void (*QemuCondWaitFunc)(QemuCond *c, QemuMutex *m, const char *f,
                                  int l);
 typedef bool (*QemuCondTimedWaitFunc)(QemuCond *c, QemuMutex *m, int ms,
                                       const char *f, int l);

 extern QemuMutexLockFunc qemu_bql_mutex_lock_func;
 extern QemuMutexLockFunc qemu_mutex_lock_func;
 extern QemuMutexTrylockFunc qemu_mutex_trylock_func;
 extern QemuRecMutexLockFunc qemu_rec_mutex_lock_func;
 extern QemuRecMutexTrylockFunc qemu_rec_mutex_trylock_func;
 extern QemuCondWaitFunc qemu_cond_wait_func;
 extern QemuCondTimedWaitFunc qemu_cond_timedwait_func;

 /* convenience macros to bypass the profiler */
 #define qemu_mutex_lock__raw(m)                         \
         qemu_mutex_lock_impl(m, __FILE__, __LINE__)
 #define qemu_mutex_trylock__raw(m)                      \
         qemu_mutex_trylock_impl(m, __FILE__, __LINE__)

 #ifdef __COVERITY__
 /*
  * Coverity is severely confused by the indirect function calls,
  * hide them.
  */
 #define qemu_mutex_lock(m)                                              \
             qemu_mutex_lock_impl(m, __FILE__, __LINE__)
 #define qemu_mutex_trylock(m)                                           \
             qemu_mutex_trylock_impl(m, __FILE__, __LINE__)
 #define qemu_rec_mutex_lock(m)                                          \
             qemu_rec_mutex_lock_impl(m, __FILE__, __LINE__)
 #define qemu_rec_mutex_trylock(m)                                       \
             qemu_rec_mutex_trylock_impl(m, __FILE__, __LINE__)
 #define qemu_cond_wait(c, m)                                            \
             qemu_cond_wait_impl(c, m, __FILE__, __LINE__)
 #define qemu_cond_timedwait(c, m, ms)                                   \
             qemu_cond_timedwait_impl(c, m, ms, __FILE__, __LINE__)
 #else
 #define qemu_mutex_lock(m) ({                                           \
             QemuMutexLockFunc _f = atomic_read(&qemu_mutex_lock_func);  \
             _f(m, __FILE__, __LINE__);                                  \
         })

 #define qemu_mutex_trylock(m) ({                                        \
             QemuMutexTrylockFunc _f = atomic_read(&qemu_mutex_trylock_func); \
             _f(m, __FILE__, __LINE__);                                  \
         })

 #define qemu_rec_mutex_lock(m) ({                                       \
             QemuRecMutexLockFunc _f = atomic_read(&qemu_rec_mutex_lock_func); \
             _f(m, __FILE__, __LINE__);                                  \
         })

 #define qemu_rec_mutex_trylock(m) ({                            \
             QemuRecMutexTrylockFunc _f;                         \
             _f = atomic_read(&qemu_rec_mutex_trylock_func);     \
             _f(m, __FILE__, __LINE__);                          \
         })

 #define qemu_cond_wait(c, m) ({                                         \
             QemuCondWaitFunc _f = atomic_read(&qemu_cond_wait_func);    \
             _f(c, m, __FILE__, __LINE__);                               \
         })

 #define qemu_cond_timedwait(c, m, ms) ({                                       \
             QemuCondTimedWaitFunc _f = atomic_read(&qemu_cond_timedwait_func); \
             _f(c, m, ms, __FILE__, __LINE__);                                  \
         })
 #endif

 #define qemu_mutex_unlock(mutex) \
         qemu_mutex_unlock_impl(mutex, __FILE__, __LINE__)

 static inline void (qemu_mutex_lock)(QemuMutex *mutex)
 {
     qemu_mutex_lock(mutex);
 }

 static inline int (qemu_mutex_trylock)(QemuMutex *mutex)
 {
     return qemu_mutex_trylock(mutex);
 }

 static inline void (qemu_mutex_unlock)(QemuMutex *mutex)
 {
     qemu_mutex_unlock(mutex);
 }

 static inline void (qemu_rec_mutex_lock)(QemuRecMutex *mutex)
 {
     qemu_rec_mutex_lock(mutex);
 }

 static inline int (qemu_rec_mutex_trylock)(QemuRecMutex *mutex)
 {
     return qemu_rec_mutex_trylock(mutex);
 }

 /* Prototypes for other functions are in thread-posix.h/thread-win32.h.  */
 void qemu_rec_mutex_init(QemuRecMutex *mutex);

 void qemu_cond_init(QemuCond *cond);
 void qemu_cond_destroy(QemuCond *cond);

 /*
  * IMPORTANT: The implementation does not guarantee that pthread_cond_signal
  * and pthread_cond_broadcast can be called except while the same mutex is
  * held as in the corresponding pthread_cond_wait calls!
  */
 void qemu_cond_signal(QemuCond *cond);
 void qemu_cond_broadcast(QemuCond *cond);
 void qemu_cond_wait_impl(QemuCond *cond, QemuMutex *mutex,
                          const char *file, const int line);
 bool qemu_cond_timedwait_impl(QemuCond *cond, QemuMutex *mutex, int ms,
                               const char *file, const int line);

 static inline void (qemu_cond_wait)(QemuCond *cond, QemuMutex *mutex)
 {
     qemu_cond_wait(cond, mutex);
 }

 /* Returns true if timeout has not expired, and false otherwise */
 static inline bool (qemu_cond_timedwait)(QemuCond *cond, QemuMutex *mutex,
                                          int ms)
 {
     return qemu_cond_timedwait(cond, mutex, ms);
 }

 void qemu_sem_init(QemuSemaphore *sem, int init);
 void qemu_sem_post(QemuSemaphore *sem);
 void qemu_sem_wait(QemuSemaphore *sem);
 int qemu_sem_timedwait(QemuSemaphore *sem, int ms);
 void qemu_sem_destroy(QemuSemaphore *sem);

 void qemu_event_init(QemuEvent *ev, bool init);
 void qemu_event_set(QemuEvent *ev);
 void qemu_event_reset(QemuEvent *ev);
 void qemu_event_wait(QemuEvent *ev);
 void qemu_event_destroy(QemuEvent *ev);

 void qemu_thread_create(QemuThread *thread, const char *name,
                         void *(*start_routine)(void *),
                         void *arg, int mode);
 void *qemu_thread_join(QemuThread *thread);
 void qemu_thread_get_self(QemuThread *thread);
 bool qemu_thread_is_self(QemuThread *thread);
 void qemu_thread_exit(void *retval);
 void qemu_thread_naming(bool enable);

 struct Notifier;
 /**
  * qemu_thread_atexit_add:
  * @notifier: Notifier to add
  *
  * Add the specified notifier to a list which will be run via
  * notifier_list_notify() when this thread exits (either by calling
  * qemu_thread_exit() or by returning from its start_routine).
  * The usual usage is that the caller passes a Notifier which is
  * a per-thread variable; it can then use the callback to free
  * other per-thread data.
  *
  * If the thread exits as part of the entire process exiting,
  * it is unspecified whether notifiers are called or not.
  */
 void qemu_thread_atexit_add(struct Notifier *notifier);
 /**
  * qemu_thread_atexit_remove:
  * @notifier: Notifier to remove
  *
  * Remove the specified notifier from the thread-exit notification
  * list. It is not valid to try to remove a notifier which is not
  * on the list.
  */
 void qemu_thread_atexit_remove(struct Notifier *notifier);

 struct QemuSpin {
     int value;
 };

 static inline void qemu_spin_init(QemuSpin *spin)
 {
     __sync_lock_release(&spin->value);
 }

 static inline void qemu_spin_lock(QemuSpin *spin)
 {
     while (unlikely(__sync_lock_test_and_set(&spin->value, true))) {
         while (atomic_read(&spin->value)) {
             cpu_relax();
         }
     }
 }

 static inline bool qemu_spin_trylock(QemuSpin *spin)
 {
     return __sync_lock_test_and_set(&spin->value, true);
 }

 static inline bool qemu_spin_locked(QemuSpin *spin)
 {
     return atomic_read(&spin->value);
 }

 static inline void qemu_spin_unlock(QemuSpin *spin)
 {
     __sync_lock_release(&spin->value);
 }

 struct QemuLockCnt {
 #ifndef CONFIG_LINUX
     QemuMutex mutex;
 #endif
     unsigned count;
 };

 /**
  * qemu_lockcnt_init: initialize a QemuLockcnt
  * @lockcnt: the lockcnt to initialize
  *
  * Initialize lockcnt's counter to zero and prepare its mutex
  * for usage.
  */
 void qemu_lockcnt_init(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_destroy: destroy a QemuLockcnt
  * @lockcnt: the lockcnt to destruct
  *
  * Destroy lockcnt's mutex.
  */
 void qemu_lockcnt_destroy(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_inc: increment a QemuLockCnt's counter
  * @lockcnt: the lockcnt to operate on
  *
  * If the lockcnt's count is zero, wait for critical sections
  * to finish and increment lockcnt's count to 1.  If the count
  * is not zero, just increment it.
  *
  * Because this function can wait on the mutex, it must not be
  * called while the lockcnt's mutex is held by the current thread.
  * For the same reason, qemu_lockcnt_inc can also contribute to
  * AB-BA deadlocks.  This is a sample deadlock scenario:
  *
  *            thread 1                      thread 2
  *            -------------------------------------------------------
  *            qemu_lockcnt_lock(&lc1);
  *                                          qemu_lockcnt_lock(&lc2);
  *            qemu_lockcnt_inc(&lc2);
  *                                          qemu_lockcnt_inc(&lc1);
  */
 void qemu_lockcnt_inc(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_dec: decrement a QemuLockCnt's counter
  * @lockcnt: the lockcnt to operate on
  */
 void qemu_lockcnt_dec(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_dec_and_lock: decrement a QemuLockCnt's counter and
  * possibly lock it.
  * @lockcnt: the lockcnt to operate on
  *
  * Decrement lockcnt's count.  If the new count is zero, lock
  * the mutex and return true.  Otherwise, return false.
  */
 bool qemu_lockcnt_dec_and_lock(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_dec_if_lock: possibly decrement a QemuLockCnt's counter and
  * lock it.
  * @lockcnt: the lockcnt to operate on
  *
  * If the count is 1, decrement the count to zero, lock
  * the mutex and return true.  Otherwise, return false.
  */
 bool qemu_lockcnt_dec_if_lock(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_lock: lock a QemuLockCnt's mutex.
  * @lockcnt: the lockcnt to operate on
  *
  * Remember that concurrent visits are not blocked unless the count is
  * also zero.  You can use qemu_lockcnt_count to check for this inside a
  * critical section.
  */
 void qemu_lockcnt_lock(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_unlock: release a QemuLockCnt's mutex.
  * @lockcnt: the lockcnt to operate on.
  */
 void qemu_lockcnt_unlock(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_inc_and_unlock: combined unlock/increment on a QemuLockCnt.
  * @lockcnt: the lockcnt to operate on.
  *
  * This is the same as
  *
  *     qemu_lockcnt_unlock(lockcnt);
  *     qemu_lockcnt_inc(lockcnt);
  *
  * but more efficient.
  */
 void qemu_lockcnt_inc_and_unlock(QemuLockCnt *lockcnt);

 /**
  * qemu_lockcnt_count: query a LockCnt's count.
  * @lockcnt: the lockcnt to query.
  *
  * Note that the count can change at any time.  Still, while the
  * lockcnt is locked, one can usefully check whether the count
  * is non-zero.
  */
 unsigned qemu_lockcnt_count(QemuLockCnt *lockcnt);

 #endif
	#ifndef QEMU_THREAD_H
	#define QEMU_THREAD_H

	#include "qemu/processor.h"
	#include "qemu/atomic.h"

	typedef struct QemuCond QemuCond;
	typedef struct QemuSemaphore QemuSemaphore;
	typedef struct QemuEvent QemuEvent;
	typedef struct QemuLockCnt QemuLockCnt;
	typedef struct QemuThread QemuThread;

	#ifdef _WIN32
	#include "qemu/thread-win32.h"
	#else
	#include "qemu/thread-posix.h"
	#endif

	/* include QSP header once QemuMutex, QemuCond etc. are defined */
	#include "qemu/qsp.h"

	#define QEMU_THREAD_JOINABLE 0
	#define QEMU_THREAD_DETACHED 1

	void qemu_mutex_init(QemuMutex *mutex);
	void qemu_mutex_destroy(QemuMutex *mutex);
	int qemu_mutex_trylock_impl(QemuMutex mutex, const char file, const int line);
	void qemu_mutex_lock_impl(QemuMutex mutex, const char file, const int line);
	void qemu_mutex_unlock_impl(QemuMutex mutex, const char file, const int line);

	typedef void (QemuMutexLockFunc)(QemuMutex m, const char *f, int l);
	typedef int (QemuMutexTrylockFunc)(QemuMutex m, const char *f, int l);
	typedef void (QemuRecMutexLockFunc)(QemuRecMutex m, const char *f, int l);
	typedef int (QemuRecMutexTrylockFunc)(QemuRecMutex m, const char *f, int l);
	typedef void (QemuCondWaitFunc)(QemuCond c, QemuMutex m, const char f,
	int l);
	typedef bool (QemuCondTimedWaitFunc)(QemuCond c, QemuMutex *m, int ms,
	const char *f, int l);

	extern QemuMutexLockFunc qemu_bql_mutex_lock_func;
	extern QemuMutexLockFunc qemu_mutex_lock_func;
	extern QemuMutexTrylockFunc qemu_mutex_trylock_func;
	extern QemuRecMutexLockFunc qemu_rec_mutex_lock_func;
	extern QemuRecMutexTrylockFunc qemu_rec_mutex_trylock_func;
	extern QemuCondWaitFunc qemu_cond_wait_func;
	extern QemuCondTimedWaitFunc qemu_cond_timedwait_func;

	/* convenience macros to bypass the profiler */
	#define qemu_mutex_lock__raw(m) \
	qemu_mutex_lock_impl(m, __FILE__, __LINE__)
	#define qemu_mutex_trylock__raw(m) \
	qemu_mutex_trylock_impl(m, __FILE__, __LINE__)

	#ifdef __COVERITY__
	/*
	* Coverity is severely confused by the indirect function calls,
	* hide them.
	*/
	#define qemu_mutex_lock(m) \
	qemu_mutex_lock_impl(m, __FILE__, __LINE__)
	#define qemu_mutex_trylock(m) \
	qemu_mutex_trylock_impl(m, __FILE__, __LINE__)
	#define qemu_rec_mutex_lock(m) \
	qemu_rec_mutex_lock_impl(m, __FILE__, __LINE__)
	#define qemu_rec_mutex_trylock(m) \
	qemu_rec_mutex_trylock_impl(m, __FILE__, __LINE__)
	#define qemu_cond_wait(c, m) \
	qemu_cond_wait_impl(c, m, __FILE__, __LINE__)
	#define qemu_cond_timedwait(c, m, ms) \
	qemu_cond_timedwait_impl(c, m, ms, __FILE__, __LINE__)
	#else
	#define qemu_mutex_lock(m) ({ \
	QemuMutexLockFunc _f = atomic_read(&qemu_mutex_lock_func); \
	_f(m, __FILE__, __LINE__); \
	})

	#define qemu_mutex_trylock(m) ({ \
	QemuMutexTrylockFunc _f = atomic_read(&qemu_mutex_trylock_func); \
	_f(m, __FILE__, __LINE__); \
	})

	#define qemu_rec_mutex_lock(m) ({ \
	QemuRecMutexLockFunc _f = atomic_read(&qemu_rec_mutex_lock_func); \
	_f(m, __FILE__, __LINE__); \
	})

	#define qemu_rec_mutex_trylock(m) ({ \
	QemuRecMutexTrylockFunc _f; \
	_f = atomic_read(&qemu_rec_mutex_trylock_func); \
	_f(m, __FILE__, __LINE__); \
	})

	#define qemu_cond_wait(c, m) ({ \
	QemuCondWaitFunc _f = atomic_read(&qemu_cond_wait_func); \
	_f(c, m, __FILE__, __LINE__); \
	})

	#define qemu_cond_timedwait(c, m, ms) ({ \
	QemuCondTimedWaitFunc _f = atomic_read(&qemu_cond_timedwait_func); \
	_f(c, m, ms, __FILE__, __LINE__); \
	})
	#endif

	#define qemu_mutex_unlock(mutex) \
	qemu_mutex_unlock_impl(mutex, __FILE__, __LINE__)

	static inline void (qemu_mutex_lock)(QemuMutex *mutex)
	{
	qemu_mutex_lock(mutex);
	}

	static inline int (qemu_mutex_trylock)(QemuMutex *mutex)
	{
	return qemu_mutex_trylock(mutex);
	}

	static inline void (qemu_mutex_unlock)(QemuMutex *mutex)
	{
	qemu_mutex_unlock(mutex);
	}

	static inline void (qemu_rec_mutex_lock)(QemuRecMutex *mutex)
	{
	qemu_rec_mutex_lock(mutex);
	}

	static inline int (qemu_rec_mutex_trylock)(QemuRecMutex *mutex)
	{
	return qemu_rec_mutex_trylock(mutex);
	}

	/* Prototypes for other functions are in thread-posix.h/thread-win32.h. */
	void qemu_rec_mutex_init(QemuRecMutex *mutex);

	void qemu_cond_init(QemuCond *cond);
	void qemu_cond_destroy(QemuCond *cond);

	/*
	* IMPORTANT: The implementation does not guarantee that pthread_cond_signal
	* and pthread_cond_broadcast can be called except while the same mutex is
	* held as in the corresponding pthread_cond_wait calls!
	*/
	void qemu_cond_signal(QemuCond *cond);
	void qemu_cond_broadcast(QemuCond *cond);
	void qemu_cond_wait_impl(QemuCond cond, QemuMutex mutex,
	const char *file, const int line);
	bool qemu_cond_timedwait_impl(QemuCond cond, QemuMutex mutex, int ms,
	const char *file, const int line);

	static inline void (qemu_cond_wait)(QemuCond cond, QemuMutex mutex)
	{
	qemu_cond_wait(cond, mutex);
	}

	/* Returns true if timeout has not expired, and false otherwise */
	static inline bool (qemu_cond_timedwait)(QemuCond cond, QemuMutex mutex,
	int ms)
	{
	return qemu_cond_timedwait(cond, mutex, ms);
	}

	void qemu_sem_init(QemuSemaphore *sem, int init);
	void qemu_sem_post(QemuSemaphore *sem);
	void qemu_sem_wait(QemuSemaphore *sem);
	int qemu_sem_timedwait(QemuSemaphore *sem, int ms);
	void qemu_sem_destroy(QemuSemaphore *sem);

	void qemu_event_init(QemuEvent *ev, bool init);
	void qemu_event_set(QemuEvent *ev);
	void qemu_event_reset(QemuEvent *ev);
	void qemu_event_wait(QemuEvent *ev);
	void qemu_event_destroy(QemuEvent *ev);

	void qemu_thread_create(QemuThread thread, const char name,
	void (start_routine)(void *),
	void *arg, int mode);
	void qemu_thread_join(QemuThread thread);
	void qemu_thread_get_self(QemuThread *thread);
	bool qemu_thread_is_self(QemuThread *thread);
	void qemu_thread_exit(void *retval);
	void qemu_thread_naming(bool enable);

	struct Notifier;
	/**
	* qemu_thread_atexit_add:
	* @notifier: Notifier to add
	*
	* Add the specified notifier to a list which will be run via
	* notifier_list_notify() when this thread exits (either by calling
	* qemu_thread_exit() or by returning from its start_routine).
	* The usual usage is that the caller passes a Notifier which is
	* a per-thread variable; it can then use the callback to free
	* other per-thread data.
	*
	* If the thread exits as part of the entire process exiting,
	* it is unspecified whether notifiers are called or not.
	*/
	void qemu_thread_atexit_add(struct Notifier *notifier);
	/**
	* qemu_thread_atexit_remove:
	* @notifier: Notifier to remove
	*
	* Remove the specified notifier from the thread-exit notification
	* list. It is not valid to try to remove a notifier which is not
	* on the list.
	*/
	void qemu_thread_atexit_remove(struct Notifier *notifier);

	struct QemuSpin {
	int value;
	};

	static inline void qemu_spin_init(QemuSpin *spin)
	{
	__sync_lock_release(&spin->value);
	}

	static inline void qemu_spin_lock(QemuSpin *spin)
	{
	while (unlikely(__sync_lock_test_and_set(&spin->value, true))) {
	while (atomic_read(&spin->value)) {
	cpu_relax();
	}
	}
	}

	static inline bool qemu_spin_trylock(QemuSpin *spin)
	{
	return __sync_lock_test_and_set(&spin->value, true);
	}

	static inline bool qemu_spin_locked(QemuSpin *spin)
	{
	return atomic_read(&spin->value);
	}

	static inline void qemu_spin_unlock(QemuSpin *spin)
	{
	__sync_lock_release(&spin->value);
	}

	struct QemuLockCnt {
	#ifndef CONFIG_LINUX
	QemuMutex mutex;
	#endif
	unsigned count;
	};

	/**
	* qemu_lockcnt_init: initialize a QemuLockcnt
	* @lockcnt: the lockcnt to initialize
	*
	* Initialize lockcnt's counter to zero and prepare its mutex
	* for usage.
	*/
	void qemu_lockcnt_init(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_destroy: destroy a QemuLockcnt
	* @lockcnt: the lockcnt to destruct
	*
	* Destroy lockcnt's mutex.
	*/
	void qemu_lockcnt_destroy(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_inc: increment a QemuLockCnt's counter
	* @lockcnt: the lockcnt to operate on
	*
	* If the lockcnt's count is zero, wait for critical sections
	* to finish and increment lockcnt's count to 1. If the count
	* is not zero, just increment it.
	*
	* Because this function can wait on the mutex, it must not be
	* called while the lockcnt's mutex is held by the current thread.
	* For the same reason, qemu_lockcnt_inc can also contribute to
	* AB-BA deadlocks. This is a sample deadlock scenario:
	*
	* thread 1 thread 2
	* -------------------------------------------------------
	* qemu_lockcnt_lock(&lc1);
	* qemu_lockcnt_lock(&lc2);
	* qemu_lockcnt_inc(&lc2);
	* qemu_lockcnt_inc(&lc1);
	*/
	void qemu_lockcnt_inc(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_dec: decrement a QemuLockCnt's counter
	* @lockcnt: the lockcnt to operate on
	*/
	void qemu_lockcnt_dec(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_dec_and_lock: decrement a QemuLockCnt's counter and
	* possibly lock it.
	* @lockcnt: the lockcnt to operate on
	*
	* Decrement lockcnt's count. If the new count is zero, lock
	* the mutex and return true. Otherwise, return false.
	*/
	bool qemu_lockcnt_dec_and_lock(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_dec_if_lock: possibly decrement a QemuLockCnt's counter and
	* lock it.
	* @lockcnt: the lockcnt to operate on
	*
	* If the count is 1, decrement the count to zero, lock
	* the mutex and return true. Otherwise, return false.
	*/
	bool qemu_lockcnt_dec_if_lock(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_lock: lock a QemuLockCnt's mutex.
	* @lockcnt: the lockcnt to operate on
	*
	* Remember that concurrent visits are not blocked unless the count is
	* also zero. You can use qemu_lockcnt_count to check for this inside a
	* critical section.
	*/
	void qemu_lockcnt_lock(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_unlock: release a QemuLockCnt's mutex.
	* @lockcnt: the lockcnt to operate on.
	*/
	void qemu_lockcnt_unlock(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_inc_and_unlock: combined unlock/increment on a QemuLockCnt.
	* @lockcnt: the lockcnt to operate on.
	*
	* This is the same as
	*
	* qemu_lockcnt_unlock(lockcnt);
	* qemu_lockcnt_inc(lockcnt);
	*
	* but more efficient.
	*/
	void qemu_lockcnt_inc_and_unlock(QemuLockCnt *lockcnt);

	/**
	* qemu_lockcnt_count: query a LockCnt's count.
	* @lockcnt: the lockcnt to query.
	*
	* Note that the count can change at any time. Still, while the
	* lockcnt is locked, one can usefully check whether the count
	* is non-zero.
	*/
	unsigned qemu_lockcnt_count(QemuLockCnt *lockcnt);

	#endif