1.\" Copyright (c) 2004 Michael Telahun Makonnen
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25.\" $FreeBSD$
26.\"
27.Dd February 19, 2004
28.Dt PTHREAD_BARRIER 3
29.Os
30.Sh NAME
31.Nm pthread_barrier_destroy , pthread_barrier_init , pthread_barrier_wait
32.Nd "destroy, initialize or wait on a barrier object"
33.Sh LIBRARY
34.Lb libpthread
35.Sh SYNOPSIS
36.In pthread.h
37.Ft int
38.Fn pthread_barrier_destroy "pthread_barrier_t *barrier"
39.Ft int
40.Fn pthread_barrier_init "pthread_barrier_t *barrier" "const pthread_barrierattr_t *attr" "unsigned count"
41.Ft int
42.Fn pthread_barrier_wait "pthread_barrier_t *barrier"
43.Sh DESCRIPTION
44The
45.Fn pthread_barrier_init
46function will initialize
47.Fa barrier
48with attributes specified in
49.Fa attr ,
50or if it is
51.Dv NULL ,
52with default attributes.
53The number of threads that must call
54.Fn pthread_barrier_wait
55before any of the waiting threads can be
56released is specified by
57.Fa count .
58The
59.Fn pthread_barrier_destroy
60function will destroy
61.Fa barrier
62and release any resources that may have been allocated on its behalf.
63.Pp
64The
65.Fn pthread_barrier_wait
66function will synchronize calling threads at
67.Fa barrier .
68The threads will be blocked from
69making further progress until
70a sufficient number of threads calls this function.
71The number of threads that must call it before
72any of them will be released is determined by the
73.Fa count
74argument to
75.Fn pthread_barrier_init .
76Once the threads have been released the barrier will be reset.
77.Sh IMPLEMENTATION NOTES
78In
79.Lb libthr
80the
81.Dv PTHREAD_BARRIER_SERIAL_THREAD
82return value will
83always be returned by the last thread to reach the barrier.
84.Sh RETURN VALUES
85If successful,
86both
87.Fn pthread_barrier_destroy
88and
89.Fn pthread_barrier_init
90will return zero.
91Otherwise, an error number will be returned to indicate the error.
92If the call to
93.Fn pthread_barrier_wait
94is successful, all but one of the threads will return zero.
95That one thread will return
96.Dv PTHREAD_BARRIER_SERIAL_THREAD .
97Otherwise, an error number will be returned to indicate the error.
98.Pp
99None of these functions will return
100.Er EINTR .
101.Sh ERRORS
102The
103.Fn pthread_barrier_destroy
104function will fail if:
105.Bl -tag -width Er
106.It Bq Er EBUSY
107An attempt was made to destroy
108.Fa barrier
109while it was in use.
110.El
111.Pp
112The
113.Fn pthread_barrier_destroy
114and
115.Fn pthread_barrier_wait
116functions may fail if:
117.Bl -tag -width Er
118.It Bq Er EINVAL
119The value specified by
120.Fa barrier
121is invalid.
122.El
123.Pp
124The
125.Fn pthread_barrier_init
126function will fail if:
127.Bl -tag -width Er
128.It Bq Er EAGAIN
129The system lacks resources,
130other than memory,
131to initialize
132.Fa barrier .
133.It Bq Er EINVAL
134The
135.Fa count
136argument is less than 1.
137.It Bq Er ENOMEM
138Insufficient memory to initialize
139.Fa barrier .
140.El
141.Sh SEE ALSO
142.Xr pthread_barrierattr 3
143.Sh HISTORY
144The
145.Fn pthread_barrier_destroy ,
146.Fn pthread_barrier_init
147and
148.Fn pthread_barrier_wait
149functions first appeared in
150.Lb libkse
151in
152.Fx 5.2 ,
153and in
154.Lb libthr
155in
156.Fx 5.3 .
157