_lwp_mutex_lock(2)						   System Calls 						_lwp_mutex_lock(2)

NAME

       _lwp_mutex_lock, _lwp_mutex_unlock, _lwp_mutex_trylock - mutual exclusion

SYNOPSIS

       #include <sys/lwp.h>

       int _lwp_mutex_lock(lwp_mutex_t *mp);

       int _lwp_mutex_trylock(lwp_mutex_t *mp);

       int _lwp_mutex_unlock(lwp_mutex_t *mp);

DESCRIPTION

       These  functions  serialize the execution of lightweight processes. They are useful for ensuring that only one lightweight process can exe-
       cute a critical section of code at any one time (mutual exclusion).  LWP mutexes must be initialized to 0 before use.

       The _lwp_mutex_lock() function locks the LWP mutex pointed to by mp. If the mutex is already locked, the calling LWP blocks until the mutex
       becomes available.  When _lwp_mutex_lock() returns, the mutex is locked and the calling LWP is the "owner".

       The  _lwp_mutex_trylock()  function  attempts  to  lock the mutex. If the mutex is already locked it returns with an error. If the mutex is
       unlocked, it is locked and _lwp_mutex_trylock() returns.

       The _lwp_mutex_unlock() function unlocks a locked mutex. The mutex must be locked and the calling LWP must be the one that last locked  the
       mutex (the owner). If any other LWPs are waiting for the mutex to become available, one of them is unblocked.

RETURN VALUES

       Upon successful completion, 0 is returned. A non-zero value indicates an error.

ERRORS

       If  any of the following conditions are detected, _lwp_mutex_lock(), _lwp_mutex_trylock(), and _lwp_mutex_unlock() fail and return the cor-
       responding value:

       EINVAL	       The mp argument points to an invalid LWP mutex.

       EFAULT	       The mp argument points to an illegal address.

       If any of the following conditions occur, _lwp_mutex_trylock() fails and returns the corresponding value:

       EBUSY	       The mp argument points to a locked mutex.

SEE ALSO

       intro(2), _lwp_cond_wait(2)

SunOS 5.10							    30 Jul 1992 						_lwp_mutex_lock(2)