Mutual Exclusion
Collaboration diagram for Mutual Exclusion:

Data Structures

Typedefs

Functions

Recursive Mutex


Detailed Description

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


Typedef Documentation

typedef int globus_rmutexattr_t

Recursive mutex attribute.


Function Documentation

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:
mutexPointer to the mutex to initialize.
attrIgnored.
Returns:
On success, globus_mutex_init() initializes the mutex and returns GLOBUS_SUCCESS. Otherwise, a non-0 value is returned.

Destroy a mutex.

The globus_mutex_destroy() function destroys the mutex pointed to by its
@a 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:
mutexThe mutex to destroy
Returns:
On success, globus_mutex_destroy() returns GLOBUS_SUCCESS. Otherwise, a non-zero implementation-specific error value is returned.

Lock a mutex.

The globus_mutex_lock() function locks the mutex pointed to by its
@a mutex parameter.
Upon successful
return, the thread calling globus_mutex_lock() has an exclusive 
lock on the resources protected by @a 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:
mutexThe mutex to lock.
Returns:
On success, globus_mutex_lock() returns GLOBUS_SUCCESS. Otherwise, a non-zero implementation-specific error value is returned.

Unlock a mutex.

The globus_mutex_unlock() function unlocks the mutex pointed to by its
@a mutex parameter.  Upon successful
return, the thread calling globus_mutex_unlock() no longer has an
exclusive lock on the resources protected by @a 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:
mutexThe mutex to unlock.
Returns:
On success, globus_mutex_unlock() returns GLOBUS_SUCCESS. Otherwise, a non-zero implementation-specific error value is returned.

Lock a mutex if it is not locked.

The globus_mutex_trylock() function locks the mutex pointed to by its
@a mutex parameter if no thread has already locked the mutex. If 
@a 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 @a 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:
mutexThe 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.

Initialize a mutex attribute.

The globus_mutexattr_init() function initializes the mutex attribute
structure pointed to by its @a 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:
attrAttribute 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.

Destroy a mutex attribute.

The globus_mutexattr_destroy() function destroys the mutex attribute
structure pointed to by its @a attr parameter. 
Parameters:
attrAttribute 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.
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:
rmutexA pointer to the mutex to initialize
rattrIGNORED
Returns:
On success, globus_rmutex_init() initializes the mutex and returns GLOBUS_SUCCESS; otherwise, it returns a non-zero error code.

Lock a recursive mutex.

The globus_rmutex_lock() function acquires the lock controlled by
@a 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:
rmutexA 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.

Unlock a recursive mutex.

The globus_rmutex_unlock() function decrements the lock count for
the lock pointed to by @a 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:
rmutexMutex to unlock
Returns:
GLOBUS_SUCCESS

Destroy a recursive mutex.

The globus_rmutex_destroy() function destroys a recursive mutex
If the mutex is currently locked, behavior is undefined.
Parameters:
rmutexMutex to unlock
Returns:
GLOBUS_SUCCESS