mariadb/storage/xtradb/include/sync0sync.ic

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*****************************************************************************/

/**************************************************//**
@file include/sync0sync.ic
Mutex, the basic synchronization primitive

Created 9/5/1995 Heikki Tuuri
*******************************************************/

/******************************************************************//**
Sets the waiters field in a mutex. */
UNIV_INTERN
void
mutex_set_waiters(
/*==============*/
	ib_mutex_t*	mutex,	/*!< in: mutex */
	ulint		n);	/*!< in: value to set */
/******************************************************************//**
Reserves a mutex or a priority mutex for the current thread. If the mutex is
reserved, the function spins a preset time (controlled by SYNC_SPIN_ROUNDS)
waiting for the mutex before suspending the thread. */
UNIV_INTERN
void
mutex_spin_wait(
/*============*/
	void*		_mutex,		/*!< in: pointer to mutex */
	bool		high_priority,	/*!< in: whether the mutex is a
					priority mutex with high priority
					specified */
	const char*	file_name,	/*!< in: file name where mutex
					requested */
	ulint		line);		/*!< in: line where requested */
#ifdef UNIV_SYNC_DEBUG
/******************************************************************//**
Sets the debug information for a reserved mutex. */
UNIV_INTERN
void
mutex_set_debug_info(
/*=================*/
	ib_mutex_t*	mutex,		/*!< in: mutex */
	const char*	file_name,	/*!< in: file where requested */
	ulint		line);		/*!< in: line where requested */
#endif /* UNIV_SYNC_DEBUG */
/******************************************************************//**
Releases the threads waiting in the primary wait array for this mutex. */
UNIV_INTERN
void
mutex_signal_object(
/*================*/
	ib_mutex_t*	mutex);	/*!< in: mutex */

/******************************************************************//**
Performs an atomic test-and-set instruction to the lock_word field of a
mutex.
@return	the previous value of lock_word: 0 or 1 */
UNIV_INLINE
byte
ib_mutex_test_and_set(
/*===============*/
	ib_mutex_t*	mutex)	/*!< in: mutex */
{
#if defined(HAVE_ATOMIC_BUILTINS)
	return(os_atomic_test_and_set_byte(&mutex->lock_word, 1));
#else
	ibool	ret;

	ret = os_fast_mutex_trylock(&(mutex->os_fast_mutex));

	if (ret == 0) {
		/* We check that os_fast_mutex_trylock does not leak
		and allow race conditions */
		ut_a(mutex->lock_word == 0);

		mutex->lock_word = 1;
	}

	return((byte) ret);
#endif
}

/******************************************************************//**
Performs a reset instruction to the lock_word field of a mutex. This
instruction also serializes memory operations to the program order. */
UNIV_INLINE
void
mutex_reset_lock_word(
/*==================*/
	ib_mutex_t*	mutex)	/*!< in: mutex */
{
#if defined(HAVE_ATOMIC_BUILTINS)
	/* In theory __sync_lock_release should be used to release the lock.
	Unfortunately, it does not work properly alone. The workaround is
	that more conservative __sync_lock_test_and_set is used instead. */
	os_atomic_test_and_set_byte(&mutex->lock_word, 0);
#else
	mutex->lock_word = 0;

	os_fast_mutex_unlock(&(mutex->os_fast_mutex));
#endif
}

/******************************************************************//**
Gets the value of the lock word. */
UNIV_INLINE
lock_word_t
mutex_get_lock_word(
/*================*/
	const ib_mutex_t*	mutex)	/*!< in: mutex */
{
	ut_ad(mutex);

	return(mutex->lock_word);
}

/******************************************************************//**
Gets the waiters field in a mutex.
@return	value to set */
UNIV_INLINE
ulint
mutex_get_waiters(
/*==============*/
	const ib_mutex_t*	mutex)	/*!< in: mutex */
{
	const volatile ulint*	ptr;	/*!< declared volatile to ensure that
					the value is read from memory */
	ut_ad(mutex);

	ptr = &(mutex->waiters);

	return(*ptr);		/* Here we assume that the read of a single
				word from memory is atomic */
}

/******************************************************************//**
NOTE! Use the corresponding macro mutex_exit(), not directly this function!
Unlocks a mutex owned by the current thread. */
UNIV_INLINE
void
mutex_exit_func(
/*============*/
	ib_mutex_t*	mutex)	/*!< in: pointer to mutex */
{
	ut_ad(mutex_own(mutex));

	ut_d(mutex->thread_id = (os_thread_id_t) ULINT_UNDEFINED);

#ifdef UNIV_SYNC_DEBUG
	sync_thread_reset_level(mutex);
#endif
	mutex_reset_lock_word(mutex);

	/* A problem: we assume that mutex_reset_lock word
	is a memory barrier, that is when we read the waiters
	field next, the read must be serialized in memory
	after the reset. A speculative processor might
	perform the read first, which could leave a waiting
	thread hanging indefinitely.

	Our current solution call every second
	sync_arr_wake_threads_if_sema_free()
	to wake up possible hanging threads if
	they are missed in mutex_signal_object. */

	if (mutex_get_waiters(mutex) != 0) {

		mutex_signal_object(mutex);
	}

#ifdef UNIV_SYNC_PERF_STAT
	mutex_exit_count++;
#endif
}

/******************************************************************//**
NOTE! Use the corresponding macro mutex_exit(), not directly this function!
Unlocks a priority mutex owned by the current thread. */
UNIV_INLINE
void
mutex_exit_func(
/*============*/
	ib_prio_mutex_t*	mutex)	/*!< in: pointer to mutex */
{
	ut_ad(mutex_own(mutex));

	ut_d(mutex->base_mutex.thread_id = (os_thread_id_t) ULINT_UNDEFINED);

#ifdef UNIV_SYNC_DEBUG
	sync_thread_reset_level(&mutex->base_mutex);
#endif
	mutex_reset_lock_word(&mutex->base_mutex);

	/* A problem: we assume that mutex_reset_lock word
	is a memory barrier, that is when we read the waiters
	field next, the read must be serialized in memory
	after the reset. A speculative processor might
	perform the read first, which could leave a waiting
	thread hanging indefinitely.

	Our current solution call every second
	sync_arr_wake_threads_if_sema_free()
	to wake up possible hanging threads if
	they are missed in mutex_signal_object. */

	/* Wake up any high priority waiters first.  */
	if (mutex->high_priority_waiters != 0) {

		mutex->high_priority_waiters = 0;
		os_event_set(mutex->high_priority_event);
		sync_array_object_signalled();

	} else if (mutex_get_waiters(&mutex->base_mutex) != 0) {

		mutex_signal_object(&mutex->base_mutex);
	}

#ifdef UNIV_SYNC_PERF_STAT
	mutex_exit_count++;
#endif

}


/******************************************************************//**
Locks a mutex for the current thread. If the mutex is reserved, the function
spins a preset time (controlled by SYNC_SPIN_ROUNDS), waiting for the mutex
before suspending the thread. */
UNIV_INLINE
void
mutex_enter_func(
/*=============*/
	ib_mutex_t*	mutex,		/*!< in: pointer to mutex */
	const char*	file_name,	/*!< in: file name where locked */
	ulint		line)		/*!< in: line where locked */
{
	ut_ad(mutex_validate(mutex));
	ut_ad(!mutex_own(mutex));

	/* Note that we do not peek at the value of lock_word before trying
	the atomic test_and_set; we could peek, and possibly save time. */

	if (!ib_mutex_test_and_set(mutex)) {
		ut_d(mutex->thread_id = os_thread_get_curr_id());
#ifdef UNIV_SYNC_DEBUG
		mutex_set_debug_info(mutex, file_name, line);
#endif
		return;	/* Succeeded! */
	}

	mutex_spin_wait(mutex, false, file_name, line);
}

/******************************************************************//**
NOTE! Use the corresponding macro in the header file, not this function
directly. Locks a priority mutex for the current thread. If the mutex is
reserved the function spins a preset time (controlled by SYNC_SPIN_ROUNDS)
waiting for the mutex before suspending the thread. If the thread is suspended,
the priority argument value determines the relative order for its wake up.  Any
IB_HIGH_PRIO waiters will be woken up before any IB_LOW_PRIO waiters.  In case
of IB_DEFAULT_PRIO, the relative priority will be set according to
srv_current_thread_priority.  */
UNIV_INLINE
void
mutex_enter_func(
/*=============*/
	ib_prio_mutex_t*	mutex,		/*!< in: pointer to mutex */
	const char*		file_name,	/*!< in: file name where
						locked */
	ulint			line,		/*!< in: line where locked */
	enum ib_sync_priority	priority)
						/*!<in: mutex acquisition
						priority */
{
	bool	high_priority;

	ut_ad(mutex_validate(&mutex->base_mutex));
	ut_ad(!mutex_own(mutex));

	/* Note that we do not peek at the value of lock_word before trying
	the atomic test_and_set; we could peek, and possibly save time. */

	if (!ib_mutex_test_and_set(&mutex->base_mutex)) {
		ut_d(mutex->base_mutex.thread_id = os_thread_get_curr_id());
#ifdef UNIV_SYNC_DEBUG
		mutex_set_debug_info(&mutex->base_mutex, file_name, line);
#endif
		return;	/* Succeeded! */
	}

	if (UNIV_LIKELY(priority == IB_DEFAULT_PRIO)) {
		high_priority = srv_current_thread_priority;
	} else {
		high_priority = (priority == IB_HIGH_PRIO);
	}
	mutex_spin_wait(mutex, high_priority, file_name, line);
}


#ifdef UNIV_PFS_MUTEX
/******************************************************************//**
NOTE! Please use the corresponding macro mutex_enter(), not directly
this function!
This is a performance schema instrumented wrapper function for
mutex_enter_func(). */
UNIV_INLINE
void
pfs_mutex_enter_func(
/*=================*/
	ib_mutex_t*	mutex,	/*!< in: pointer to mutex */
	const char*	file_name,	/*!< in: file name where locked */
	ulint		line)		/*!< in: line where locked */
{
	if (mutex->pfs_psi != NULL) {
		PSI_mutex_locker*	locker;
		PSI_mutex_locker_state	state;

		locker = PSI_MUTEX_CALL(start_mutex_wait)(
			&state, mutex->pfs_psi,
			PSI_MUTEX_LOCK, file_name, line);

		mutex_enter_func(mutex, file_name, line);

		if (locker != NULL) {
			PSI_MUTEX_CALL(end_mutex_wait)(locker, 0);
		}
	} else {
		mutex_enter_func(mutex, file_name, line);
	}
}

/******************************************************************//**
NOTE! Please use the corresponding macro mutex_enter(), not directly
this function!
This is a performance schema instrumented wrapper function for
mutex_enter_func(). */
UNIV_INLINE
void
pfs_mutex_enter_func(
/*=================*/
	ib_prio_mutex_t*	mutex,		/*!< in: pointer to mutex */
	const char*		file_name,	/*!< in: file name where
						locked */
	ulint			line,		/*!< in: line where locked */
	enum ib_sync_priority	priority)	/*!<in: mutex acquisition
						priority */
{
	if (mutex->base_mutex.pfs_psi != NULL) {
		PSI_mutex_locker*	locker;
		PSI_mutex_locker_state	state;

		locker = PSI_MUTEX_CALL(start_mutex_wait)(
			&state, mutex->base_mutex.pfs_psi,
			PSI_MUTEX_LOCK, file_name, line);

		mutex_enter_func(mutex, file_name, line, priority);

		if (locker != NULL) {
			PSI_MUTEX_CALL(end_mutex_wait)(locker, 0);
		}
	} else {
		mutex_enter_func(mutex, file_name, line, priority);
	}
}

/********************************************************************//**
NOTE! Please use the corresponding macro mutex_enter_nowait(), not directly
this function!
This is a performance schema instrumented wrapper function for
mutex_enter_nowait_func.
@return 0 if succeed, 1 if not */
UNIV_INLINE
ulint
pfs_mutex_enter_nowait_func(
/*========================*/
	ib_mutex_t*	mutex,		/*!< in: pointer to mutex */
	const char*	file_name,	/*!< in: file name where mutex
					requested */
	ulint		line)		/*!< in: line where requested */
{
	ulint		ret;

	if (mutex->pfs_psi != NULL) {
		PSI_mutex_locker*	locker;
		PSI_mutex_locker_state		state;

		locker = PSI_MUTEX_CALL(start_mutex_wait)(
			&state, mutex->pfs_psi,
			PSI_MUTEX_TRYLOCK, file_name, line);

		ret = mutex_enter_nowait_func(mutex, file_name, line);

		if (locker != NULL) {
			PSI_MUTEX_CALL(end_mutex_wait)(locker, (int) ret);
		}
	} else {
		ret = mutex_enter_nowait_func(mutex, file_name, line);
	}

	return(ret);
}

/********************************************************************//**
NOTE! Please use the corresponding macro mutex_enter_nowait(), not directly
this function!
This is a performance schema instrumented wrapper function for
mutex_enter_nowait_func.
@return	0 if succeed, 1 if not */
UNIV_INLINE
ulint
pfs_mutex_enter_nowait_func(
/*========================*/
	ib_prio_mutex_t*	mutex,		/*!< in: pointer to mutex */
	const char*		file_name,	/*!< in: file name where mutex
						  requested */
	ulint			line)		/*!< in: line where
						  requested */
{
	return pfs_mutex_enter_nowait_func(&mutex->base_mutex, file_name,
					   line);
}

/******************************************************************//**
NOTE! Please use the corresponding macro mutex_exit(), not directly
this function!
A wrap function of mutex_exit_func() with performance schema instrumentation.
Unlocks a mutex owned by the current thread. */
UNIV_INLINE
void
pfs_mutex_exit_func(
/*================*/
	ib_mutex_t*	mutex)	/*!< in: pointer to mutex */
{
	if (mutex->pfs_psi != NULL) {
		PSI_MUTEX_CALL(unlock_mutex)(mutex->pfs_psi);
	}

	mutex_exit_func(mutex);
}

/******************************************************************//**
NOTE! Please use the corresponding macro mutex_exit(), not directly
this function!
A wrap function of mutex_exit_func() with peformance schema instrumentation.
Unlocks a priority mutex owned by the current thread. */
UNIV_INLINE
void
pfs_mutex_exit_func(
/*================*/
	ib_prio_mutex_t*	mutex)	/*!< in: pointer to mutex */
{
	if (mutex->base_mutex.pfs_psi != NULL) {
		PSI_MUTEX_CALL(unlock_mutex)(mutex->base_mutex.pfs_psi);
	}

	mutex_exit_func(mutex);
}


/******************************************************************//**
NOTE! Please use the corresponding macro mutex_create(), not directly
this function!
A wrapper function for mutex_create_func(), registers the mutex
with performance schema if "UNIV_PFS_MUTEX" is defined when
creating the mutex */
UNIV_INLINE
void
pfs_mutex_create_func(
/*==================*/
	mysql_pfs_key_t	key,		/*!< in: Performance Schema key */
	ib_mutex_t*	mutex,		/*!< in: pointer to memory */
# ifdef UNIV_DEBUG
#  ifdef UNIV_SYNC_DEBUG
	ulint		level,		/*!< in: level */
#  endif /* UNIV_SYNC_DEBUG */
	const char*	cfile_name,	/*!< in: file name where created */
	ulint		cline,		/*!< in: file line where created */
# endif /* UNIV_DEBUG */
	const char*	cmutex_name)	/*!< in: mutex name */
{
	mutex->pfs_psi = PSI_MUTEX_CALL(init_mutex)(key, mutex);

	mutex_create_func(mutex,
# ifdef UNIV_DEBUG
#  ifdef UNIV_SYNC_DEBUG
			  level,
#  endif /* UNIV_SYNC_DEBUG */
			  cfile_name,
			  cline,
# endif /* UNIV_DEBUG */
			  cmutex_name);
}

/******************************************************************//**
NOTE! Please use the corresponding macro mutex_create(), not directly
this function!
A wrapper function for mutex_create_func(), registers the mutex
with peformance schema if "UNIV_PFS_MUTEX" is defined when
creating the performance mutex */
UNIV_INLINE
void
pfs_mutex_create_func(
/*==================*/
	PSI_mutex_key		key,		/*!< in: Performance Schema
						key */
	ib_prio_mutex_t*	mutex,		/*!< in: pointer to memory */
# ifdef UNIV_DEBUG
#  ifdef UNIV_SYNC_DEBUG
	ulint			level,		/*!< in: level */
#  endif /* UNIV_SYNC_DEBUG */
	const char*		cfile_name,	/*!< in: file name where
						created */
	ulint			cline,		/*!< in: file line where
						  created */
# endif /* UNIV_DEBUG */
	const char*		cmutex_name)
{
	mutex->base_mutex.pfs_psi = PSI_MUTEX_CALL(init_mutex)(key, mutex);

	mutex_create_func(mutex,
# ifdef UNIV_DEBUG
#  ifdef UNIV_SYNC_DEBUG
			  level,
#  endif /* UNIV_SYNC_DEBUG */
			  cfile_name,
			  cline,
# endif /* UNIV_DEBUG */
			  cmutex_name);
}


/******************************************************************//**
NOTE! Please use the corresponding macro mutex_free(), not directly
this function!
Wrapper function for mutex_free_func(). Also destroys the performance
schema probes when freeing the mutex */
UNIV_INLINE
void
pfs_mutex_free_func(
/*================*/
	ib_mutex_t*	mutex)	/*!< in: mutex */
{
	if (mutex->pfs_psi != NULL) {
		PSI_MUTEX_CALL(destroy_mutex)(mutex->pfs_psi);
		mutex->pfs_psi = NULL;
	}

	mutex_free_func(mutex);
}

/******************************************************************//**
NOTE! Please use the corresponding macro mutex_free(), not directly
this function!
Wrapper function for mutex_free_func(). Also destroys the performance
schema probes when freeing the priority mutex */
UNIV_INLINE
void
pfs_mutex_free_func(
/*================*/
	ib_prio_mutex_t*	mutex)	/*!< in: mutex */
{
	if (mutex->base_mutex.pfs_psi != NULL) {
		PSI_MUTEX_CALL(destroy_mutex)(mutex->base_mutex.pfs_psi);
		mutex->base_mutex.pfs_psi = NULL;
	}

	mutex_free_func(mutex);
}


#endif /* UNIV_PFS_MUTEX */

#ifndef HAVE_ATOMIC_BUILTINS
/**********************************************************//**
Function that uses a mutex to decrement a variable atomically */
UNIV_INLINE
void
os_atomic_dec_ulint_func(
/*=====================*/
	ib_mutex_t*	mutex,		/*!< in: mutex guarding the dec */
	volatile ulint*	var,		/*!< in/out: variable to decrement */
	ulint		delta)		/*!< in: delta to decrement */
{
	mutex_enter(mutex);

	/* I don't think we will encounter a situation where
	this check will not be required. */
	ut_ad(*var >= delta);

	*var -= delta;

	mutex_exit(mutex);
}

/**********************************************************//**
Function that uses a mutex to increment a variable atomically */
UNIV_INLINE
void
os_atomic_inc_ulint_func(
/*=====================*/
	ib_mutex_t*	mutex,		/*!< in: mutex guarding the increment */
	volatile ulint*	var,		/*!< in/out: variable to increment */
	ulint		delta)		/*!< in: delta to increment */
{
	mutex_enter(mutex);

	*var += delta;

	mutex_exit(mutex);
}
#endif /* !HAVE_ATOMIC_BUILTINS */