_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
execute 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
corresponding 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)

July 30, 1992 _LWP_MUTEX_LOCK(2)