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_lwp_mutex_lock(2) [opensolaris man page]

_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 5.11 30 Jul 1992 _lwp_mutex_lock(2)

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_lwp_cond_wait(2)						   System Calls 						 _lwp_cond_wait(2)

NAME
_lwp_cond_wait, _lwp_cond_timedwait, _lwp_cond_reltimedwait - wait on a condition variable SYNOPSIS
#include <sys/lwp.h> int _lwp_cond_wait(lwp_cond_t *cvp, lwp_mutex_t *mp); int _lwp_cond_timedwait(lwp_cond_t *cvp, lwp_mutex_t *mp, timestruc_t *abstime); int _lwp_cond_reltimedwait(lwp_cond_t *cvp, lwp_mutex_t *mp, timestruc_t *reltime); DESCRIPTION
These functions are used to wait for the occurrence of a condition represented by an LWP condition variable. LWP condition variables must be initialized to 0 before use. The _lwp_cond_wait() function atomically releases the LWP mutex pointed to by mp and causes the calling LWP to block on the LWP condition variable pointed to by cvp. The blocked LWP may be awakened by _lwp_cond_signal(2), _lwp_cond_broadcast(2), or when interrupted by delivery of a signal. Any change in value of a condition associated with the condition variable cannot be inferred by the return of _lwp_cond_wait() and any such condition must be re-evaluated. The _lwp_cond_timedwait() function is similar to _lwp_cond_wait(), except that the calling LWP will not block past the time of day speci- fied by abstime. If the time of day becomes greater than abstime, _lwp_cond_timedwait() returns with the error code ETIME. The _lwp_cond_reltimedwait() function is similar to _lwp_cond_wait(), except that the calling LWP will not block past the relative time specified by reltime. If the time of day becomes greater than the starting time of day plus reltime, _lwp_cond_reltimedwait() returns with the error code ETIME. The _lwp_cond_wait(), _lwp_cond_timedwait(), and _lwp_cond_reltimedwait() functions always return with the mutex locked and owned by the calling lightweight process. 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_cond_wait(), _lwp_cond_timedwait(), and _lwp_cond_reltimedwait() fail and return the corresponding value: EINVAL The cvp argument points to an invalid LWP condition variable or the mp argument points to an invalid LWP mutex. EFAULT The mp, cvp, or abstime argument points to an illegal address. If any of the following conditions occur, _lwp_cond_wait(), _lwp_cond_timedwait(), and _lwp_cond_reltimedwait() fail and return the corre- sponding value: EINTR The call was interrupted by a signal or fork(2). If any of the following conditions occur, _lwp_cond_timedwait() and _lwp_cond_reltimedwait() fail and return the corresponding value: ETIME The time specified inabstime or reltime has passed. EXAMPLES
Example 1 Use the _lwp_cond_wait() function in a loop testing some condition. The _lwp_cond_wait() function is normally used in a loop testing some condition, as follows: lwp_mutex_t m; lwp_cond_t cv; int cond; (void) _lwp_mutex_lock(&m); while (cond == FALSE) { (void) _lwp_cond_wait(&cv, &m); } (void) _lwp_mutex_unlock(&m); Example 2 Use the _lwp_cond_timedwait() function in a loop testing some condition. The _lwp_cond_timedwait() function is also normally used in a loop testing some condition. It uses an absolute timeout value as follows: timestruc_t to; lwp_mutex_t m; lwp_cond_t cv; int cond, err; (void) _lwp_mutex_lock(&m); to.tv_sec = time(NULL) + TIMEOUT; to.tv_nsec = 0; while (cond == FALSE) { err = _lwp_cond_timedwait(&cv, &m, &to); if (err == ETIME) { /* timeout, do something */ break; SENDwhom} } (void) _lwp_mutex_unlock(&m); This example sets a bound on the total wait time even though the _lwp_cond_timedwait() may return several times due to the condition being signalled or the wait being interrupted. Example 3 Use the _lwp_cond_reltimedwait() function in a loop testing some condition. The _lwp_cond_reltimedwait() function is also normally used in a loop testing some condition. It uses a relative timeout value as follows: timestruc_t to; lwp_mutex_t m; lwp_cond_t cv; int cond, err; (void) _lwp_mutex_lock(&m); while (cond == FALSE) { to.tv_sec = TIMEOUT; to.tv_nsec = 0; err = _lwp_cond_reltimedwait(&cv, &m, &to); if (err == ETIME) { /* timeout, do something */ break; } } (void) _lwp_mutex_unlock(&m); SEE ALSO
_lwp_cond_broadcast(2), _lwp_cond_signal(2), _lwp_kill(2), _lwp_mutex_lock(2), fork(2), kill(2) SunOS 5.11 13 Apr 2001 _lwp_cond_wait(2)
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