Mutual Exclusion

Data Structures
union	globus_mutex_t
	Mutex. More...
union	globus_mutexattr_t
	Mutex attribute. More...
struct	globus_rmutex_t
	Recursive Mutex. More...

Typedefs
typedef int	globus_rmutexattr_t
	Recursive mutex attribute.

Functions
int	globus_mutex_init (globus_mutex_t *mutex, globus_mutexattr_t *attr)
	Initialize a mutex. More...
int	globus_mutex_destroy (globus_mutex_t *mutex)
	Destroy a mutex. More...
int	globus_mutex_lock (globus_mutex_t *mutex)
	Lock a mutex. More...
int	globus_mutex_unlock (globus_mutex_t *mutex)
	Unlock a mutex. More...
int	globus_mutex_trylock (globus_mutex_t *mutex)
	Lock a mutex if it is not locked. More...
int	globus_mutexattr_init (globus_mutexattr_t *attr)
	Initialize a mutex attribute. More...
int	globus_mutexattr_destroy (globus_mutexattr_t *attr)
	Destroy a mutex attribute. More...

Recursive Mutex
int	globus_rmutex_init (globus_rmutex_t *rmutex, globus_rmutexattr_t *rattr)
	Initialize a recursive mutex. More...
int	globus_rmutex_lock (globus_rmutex_t *rmutex)
	Lock a recursive mutex. More...
int	globus_rmutex_unlock (globus_rmutex_t *rmutex)
	Unlock a recursive mutex. More...
int	globus_rmutex_destroy (globus_rmutex_t *rmutex)
	Destroy a recursive mutex. More...

Detailed Description

The Globus runtime includes three portable, related mutual exclusion primitives that can be used in applications and libraries. These are

• globus_mutex_t: a non-recursive, non-shared lock
• globus_rmutex_t: a recursive non-shared lock
• globus_rw_mutex_t: a reader-writer lock

Function Documentation

globus_mutex_destroy()

int globus_mutex_destroy

(

globus_mutex_t *

mutex

)

Destroy a mutex.

The globus_mutex_destroy() function destroys the mutex pointed to by its mutex parameter. After a mutex is destroyed it may no longer be used unless it is again initialized by globus_mutex_init(). Behavior is undefined if globus_mutex_destroy() is called with a pointer to a locked mutex.

Parameters

mutex

The mutex to destroy

Returns

On success, globus_mutex_destroy() returns GLOBUS_SUCCESS. Otherwise, a non-zero implementation-specific error value is returned.

globus_mutex_init()

int globus_mutex_init	(	globus_mutex_t *	mutex,
		globus_mutexattr_t *	attr
	)

Initialize a mutex.

The globus_mutex_init() function creates a mutex variable that can be used for synchronization. Currently, the attr parameter is ignored.

Parameters

mutex	Pointer to the mutex to initialize.
attr	Ignored.

Returns

On success, globus_mutex_init() initializes the mutex and returns GLOBUS_SUCCESS. Otherwise, a non-0 value is returned.

globus_mutex_lock()

int globus_mutex_lock

(

globus_mutex_t *

mutex

)

Lock a mutex.

The globus_mutex_lock() function locks the mutex pointed to by its mutex parameter.

Upon successful return, the thread calling globus_mutex_lock() has an exclusive lock on the resources protected by mutex. Other threads calling globus_mutex_lock() will wait until that thread later calls globus_mutex_unlock() or globus_cond_wait() with that mutex. Depending on the thread model, calling globus_mutex_lock on a mutex locked by the current thread will either return an error or result in deadlock.

Parameters

mutex

The mutex to lock.

Returns

On success, globus_mutex_lock() returns GLOBUS_SUCCESS. Otherwise, a non-zero implementation-specific error value is returned.

globus_mutex_trylock()

int globus_mutex_trylock

(

globus_mutex_t *

mutex

)

Lock a mutex if it is not locked.

The globus_mutex_trylock() function locks the mutex pointed to by its mutex parameter if no thread has already locked the mutex. If mutex is locked, then globus_mutex_trylock() returns EBUSY and does not block the current thread or lock the mutex. Upon successful return, the thread calling globus_mutex_trylock() has an exclusive lock on the resources protected by mutex. Other threads calling globus_mutex_lock() will wait until that thread later calls globus_mutex_unlock() or globus_cond_wait() with that mutex.

Parameters

mutex

The mutex to lock.

Returns

On success, globus_mutex_trylock() returns GLOBUS_SUCCESS and locks the mutex. If another thread holds the lock, globus_mutex_trylock() returns EBUSY. Otherwise, a non-zero implementation-specific error value is returned.

globus_mutex_unlock()

int globus_mutex_unlock

(

globus_mutex_t *

mutex

)

Unlock a mutex.

The globus_mutex_unlock() function unlocks the mutex pointed to by its mutex parameter. Upon successful return, the thread calling globus_mutex_unlock() no longer has an exclusive lock on the resources protected by mutex. Another thread calling globus_mutex_lock() may be unblocked so that it may acquire the mutex. Behavior is undefined if globus_mutex_unlock is called with an unlocked mutex.

Parameters

mutex

The mutex to unlock.

Returns

On success, globus_mutex_unlock() returns GLOBUS_SUCCESS. Otherwise, a non-zero implementation-specific error value is returned.

globus_mutexattr_destroy()

int globus_mutexattr_destroy

(

globus_mutexattr_t *

attr

)

Destroy a mutex attribute.

The globus_mutexattr_destroy() function destroys the mutex attribute structure pointed to by its attr parameter.

Parameters

attr	Attribute structure to destroy.

Returns

Upon success, globus_mutexattr_destroy() returns GLOBUS_SUCCESS and modifies the attribute pointed to by attr. If an error occurs, globus_mutexattr_destroy() returns an implementation-specific non-zero error code.

globus_mutexattr_init()

int globus_mutexattr_init

(

globus_mutexattr_t *

attr

)

Initialize a mutex attribute.

The globus_mutexattr_init() function initializes the mutex attribute structure pointed to by its attr parameter. Currently there are no attribute values that can be set via this API, so there's no real use to calling this function.

Parameters

attr	Attribute structure to initialize.

Returns

Upon success, globus_mutexattr_init() returns GLOBUS_SUCCESS and modifies the attribute pointed to by attr. If an error occurs, globus_mutexattr_init() returns an implementation-specific non-zero error code.

globus_rmutex_destroy()

int globus_rmutex_destroy

(

globus_rmutex_t *

rmutex

)

Destroy a recursive mutex.

The globus_rmutex_destroy() function destroys a recursive mutex If the mutex is currently locked, behavior is undefined.

Parameters

rmutex

Mutex to unlock

Returns

GLOBUS_SUCCESS

globus_rmutex_init()

int globus_rmutex_init	(	globus_rmutex_t *	rmutex,
		globus_rmutexattr_t *	rattr
	)

Initialize a recursive mutex.

The globus_rmutex_init() function initializes a recursive mutex, that is, one which may be locked multiple times by a single thread without causing deadlock.

Parameters

rmutex	A pointer to the mutex to initialize
rattr	IGNORED

Returns

On success, globus_rmutex_init() initializes the mutex and returns GLOBUS_SUCCESS; otherwise, it returns a non-zero error code.

globus_rmutex_lock()

int globus_rmutex_lock

(

globus_rmutex_t *

rmutex

)

Lock a recursive mutex.

The globus_rmutex_lock() function acquires the lock controlled by rmutex. This may be called multiple times in a single thread without causing deadlock, provided that a call to globus_rmutex_unlock() is called the same number of times as globus_rmutex_lock(). Once acquired, all other threads calling this function will be blocked until the mutex is completely unlocked.

Parameters

rmutex

A pointer to the mutex to lock

Returns

On success, globus_rmutex_init() increases the lock level for the mutex, blocks other threads trying to acquire the same mutex, and returns GLOBUS_SUCCESS; otherwise, it returns a non-zero error code.

globus_rmutex_unlock()

int globus_rmutex_unlock

(

globus_rmutex_t *

rmutex

)

Unlock a recursive mutex.

The globus_rmutex_unlock() function decrements the lock count for the lock pointed to by rmutex. If the lock count is reduced to zero, it also unblocks a thread which is trying to acquire the lock if there is one.

Parameters

rmutex

Mutex to unlock

Returns

GLOBUS_SUCCESS