cond_signal(SYNCH)

cond_signal -- wake up a single thread waiting on a condition variable

Synopsis

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

   int cond_signal(cond_t *cond);

Description

cond_signal wakes up a single thread, if one exists, waiting on the condition cond. If more than one thread is waiting, the choice of which to release from the blocked group is scheduling policy-specific: Bound threads have priority over multiplexed threads; then within each category the choice of thread is scheduling-policy-specific.

cond_signal has no effect if there are no threads waiting on cond.

A cond_signal will be more reliable if the associated mutex used by waiters is held across the call.

Parameters

cond: pointer to condition variable to be signaled

cond parameter

The condition variable denoted by cond must previously have been initialized (see cond_init(SYNCH)).

Usage

See the description of how to use condition variables under USAGE on condition(SYNCH).

Return values

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

Errors

If any of the following conditions is detected, cond_signal returns the corresponding value:

EINVAL: invalid argument specified

References

condition(SYNCH), cond_broadcast(SYNCH), cond_destroy(SYNCH), cond_init(SYNCH), cond_timedwait(SYNCH), cond_wait(SYNCH), Intro(SYNCH)