mutex_init(3T)

#include <synch.h>   (or
#include <thread.h>)

int mutex_init(mutex_t *mp, int type, void *arg)); 

Use mutex_init() to initialize the mutex pointed to by mp. The type can be one of the following (note that arg is currently ignored).

• USYNC_PROCESS The mutex can be used to synchronize threads in this and other processes.

• USYNC_THREAD The mutex can be used to synchronize threads in this process, only.

Mutexes can also be initialized by allocation in zeroed memory, in which case a type of USYNC_THREAD is assumed.

Multiple threads must not initialize the same mutex simultaneously. A mutex lock must not be reinitialized while other threads might be using it.

Mutexes with Intraprocess Scope

#include <thread.h>

mutex_t mp;
int ret;

/* to be used within this process only */
ret = mutex_init(&mp, USYNC_THREAD, 0); 

Mutexes with Interprocess Scope

#include <thread.h>

mutex_t mp;
int ret;

/* to be used among all processes */
ret = mutex_init(&mp, USYNC_PROCESS, 0);