_lwp_cond_signal(2) System Calls _lwp_cond_signal(2)NAME
_lwp_cond_signal, _lwp_cond_broadcast - signal a condition variable
SYNOPSIS
#include <sys/lwp.h>
int _lwp_cond_signal(lwp_cond_t *cvp);
int _lwp_cond_broadcast(lwp_cond_t *cvp);
DESCRIPTION
The _lwp_cond_signal() function unblocks one LWP that is blocked on the LWP condition variable pointed to by cvp.
The _lwp_cond_broadcast() function unblocks all LWPs that are blocked on the LWP condition variable pointed to by cvp.
If no LWPs are blocked on the LWP condition variable, then _lwp_cond_signal() and _lwp_cond_broadcast() have no effect.
Both functions should be called under the protection of the same LWP mutex lock that is used with the LWP condition variable being sig-
naled. Otherwise, the condition variable may be signalled between the test of the associated condition and blocking in _lwp_cond_wait().
This can cause an infinite wait.
RETURN VALUES
Upon successful completion, 0 is returned. A non-zero value indicates an error.
ERRORS
The _lwp_cond_signal() and _lwp_cond_broadcast() functions will fail if:
EINVAL The cvp argument points to an invalid LWP condition variable.
EFAULT The cvp argument points to an invalid address.
SEE ALSO _lwp_cond_wait(2), _lwp_mutex_lock(2)SunOS 5.10 8 Dec 1995 _lwp_cond_signal(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)