forksafe_mutex

Initialize a forksafe mutex

Synopsis:

#include <forksafe_mutex.h>

forksafe_mutex_t mutex = FORKSAFE_MUTEX_INITIALIZER;

int forksafe_mutex_init(
            forksafe_mutex_t* mutex,
            const pthread_mutexattr_t* attr );

Arguments:

mutex: A pointer to the forksafe_mutex_t object that you want to initialize.
Note: It's always safe, and typically faster, to assure that mutex is 32-bit aligned.
attr: NULL, or a pointer to a pthread_mutexattr_t object that specifies the attributes that you want to use for the mutex. For more information, see pthread_mutexattr_init().

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The forksafe_mutex_init() function initializes the given forksafe mutex object, using the attributes specified by the mutex attributes object attr. If attr is NULL, then the mutex is initialized with the default attributes (see pthread_mutexattr_init()). After initialization, the mutex is in an unlocked state.

CAUTION:

You should allocate synchronization objects only in normal memory mappings. On certain processors, atomic operations such as calls to forksafe_mutex_lock() will cause a fault if the control structure is allocated in uncached memory.

You can initialize a statically allocated mutex with the default attributes by assigning to it the macro FORKSAFE_MUTEX_INITIALIZER or FORKSAFE_RMUTEX_INITIALIZER (for recursive mutexes).

Note: To destroy a mutex, call forksafe_mutex_destroy(). Once you've destroyed a mutex, don't reuse it without reinitializing it by calling forksafe_mutex_init().

For more information about forksafe mutexes, see “Using fork() in a multithreaded process” in the “Processes and Threads” chapter of Getting Started with QNX Neutrino.

Returns:

EOK: Success.
EFAULT: A fault occurred when the kernel tried to access mutex or attr.
EINVAL: The value specified by attr is invalid.
ENOMEM: All kernel synchronization objects are in use.

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes