mutex_lock(SYNCH)

mutex_lock -- lock a mutex

Synopsis

   cc [options] -Kthread file
   
   #include <synch.h>
   

   int mutex_lock(mutex_t *mutex);

Description

mutex_lock locks the mutual exclusion lock (mutex) pointed to by mutex. If mutex is locked, the calling thread is blocked until mutex becomes available. When mutex_lock returns successfully, the caller has locked mutex.

Parameters

mutex: pointer to mutex to be locked

mutex must previously have been initialized, either by mutex_init, or statically (see mutex_init(SYNCH)).

From the point of view of the caller, mutex_lock is atomic: even if interrupted by a signal or forkall (see fork(S)), mutex_lock will not return until it holds the locked mutex. As a consequence, if mutex_lock is interrupted, an error indication such as EINTR is never returned to the caller.

Usage

Mutexes acquired with mutex_lock should be released with mutex_unlock.

Return values

mutex_lock returns zero for success and an error number for failure.

Errors

If the following condition is detected, mutex_lock returns the corresponding value:

EINVAL: invalid argument specified

Warnings

If a thread exits while holding a mutex, the mutex will not be unlocked, and other threads waiting for the mutex will wait forever. Similarly, if a process exits while holding a USYNC_PROCESS mutex, the mutex will not be unlocked, and other processes or threads waiting for the mutex will wait forever.

References

fork(S), Intro(SYNCH), mutex(SYNCH), mutex_destroy(SYNCH), mutex_init(SYNCH), mutex_trylock(SYNCH), mutex_unlock(SYNCH)