Multithreaded Programming Guide

Set the Scope of a Mutex


pthread_mutexattr_setpshared(3T) sets the scope of the mutex variable.

The scope of a mutex variable can be either process private (intraprocess) or system wide (interprocess). If the mutex is created with the pshared attribute set to the PTHREAD_PROCESS_SHARED state, and it exists in shared memory, it can be shared among threads from more than one process. This is equivalent to the USYNC_PROCESS flag in mutex_init() in the original Solaris threads.

int	pthread_mutexattr_setpshared(pthread_mutexattr_t *mattr,
    int pshared);
#include <pthread.h>

pthread_mutexattr_t mattr;
int ret;

ret = pthread_mutexattr_init(&mattr);
 * resetting to its default value: private
ret = pthread_mutexattr_setpshared(&mattr,

If the mutex pshared attribute is set to PTHREAD_PROCESS_PRIVATE, only those threads created by the same process can operate on the mutex.

Return Values

Returns zero after completing successfully. Any other returned value indicates that an error occurred. If the following condition occurs, the function fails and returns the corresponding value.


The value specified by mattr is invalid.