pthread_mutexattr_setpshared(3C) sets the scope of the mutex variable.
int pthread_mutexattr_setpshared(pthread_mutexattr_t *restrict mattr, int *restrict 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, PTHREAD_PROCESS_PRIVATE);
The scope of a mutex variable can be either process private (intraprocess) or system wide (interprocess). To share the mutex among threads from more than one process, create the mutex in shared memory with the pshared attribute set to PTHREAD_PROCESS_SHARED .
If the mutex pshared attribute is set to PTHREAD_PROCESS_PRIVATE , only those threads created by the same process can operate on the mutex.
pthread_mutexattr_setpshared() returns zero after completing successfully. Any other return 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.