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.TH PTHREAD_COND_SIGNAL 3C "Mar 23, 2005"
.SH NAME
pthread_cond_signal, pthread_cond_broadcast \- signal or broadcast a condition
.SH SYNOPSIS
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ]
#include <pthread.h>

\fBint\fR \fBpthread_cond_signal\fR(\fBpthread_cond_t *\fR\fIcond\fR);
.fi

.LP
.nf
\fBint\fR \fBpthread_cond_broadcast\fR(\fBpthread_cond_t *\fR\fIcond\fR);
.fi

.SH DESCRIPTION
.sp
.LP
These two functions are used to unblock threads blocked on a condition
variable.
.sp
.LP
The \fBpthread_cond_signal()\fR call unblocks at least one of the threads that
are blocked on the specified condition variable \fIcond\fR (if any threads are
blocked on \fIcond\fR).
.sp
.LP
The \fBpthread_cond_broadcast()\fR call unblocks all threads currently blocked
on the specified condition variable \fIcond\fR.
.sp
.LP
If more than one thread is blocked on a condition variable, the scheduling
policy determines the order in which threads are unblocked. When each thread
unblocked as a result of a \fBpthread_cond_signal()\fR or
\fBpthread_cond_broadcast()\fR returns from its call to
\fBpthread_cond_wait()\fR or \fBpthread_cond_timedwait()\fR, the thread owns
the mutex with which it called \fBpthread_cond_wait()\fR or
\fBpthread_cond_timedwait()\fR. The thread(s) that are unblocked contend for
the mutex according to the scheduling policy (if applicable), and as if each
had called \fBpthread_mutex_lock()\fR.
.sp
.LP
The \fBpthread_cond_signal()\fR or \fBpthread_cond_broadcast()\fR functions may
be called by a thread whether or not it currently owns the mutex that threads
calling \fBpthread_cond_wait()\fR or \fBpthread_cond_timedwait()\fR have
associated with the condition variable during their waits; however, if
predictable scheduling behavior is required, then that mutex is locked by the
thread calling \fBpthread_cond_signal()\fR or \fBpthread_cond_broadcast()\fR.
.sp
.LP
The \fBpthread_cond_signal()\fR and \fBpthread_cond_broadcast()\fR functions
have no effect if there are no threads currently blocked on \fIcond\fR.
.SH RETURN VALUES
.sp
.LP
If successful, the \fBpthread_cond_signal()\fR and
\fBpthread_cond_broadcast()\fR functions return  \fB0\fR. Otherwise, an error
number is returned to indicate the error.
.SH ERRORS
.sp
.LP
The  \fBpthread_cond_signal()\fR and \fBpthread_cond_broadcast()\fR function
may fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value \fIcond\fR does not refer to an initialized condition variable.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBpthread_cond_init\fR(3C), \fBpthread_cond_wait\fR(3C),
\fBpthread_cond_timedwait\fR(3C), \fBattributes\fR(5), \fBcondition\fR(5),
\fBstandards\fR(5)