sem_post.3 (7a6d1e6f69df3ecccbc86b40f24ee28126c2da11) sem_post.3 (b0a1b4f80919d734dda03410df0cabf7297dfb68)
1.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>.
1.\" Copyright (C) 2000 Jason Evans <jasone@canonware.com>.
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28.\" $FreeBSD$
28.\" $FreeBSD$
29.\"
30.Dd February 15, 2000
31.Dt SEM_POST 3
32.Os
33.Sh NAME
34.Nm sem_post
35.Nd increment (unlock) a semaphore
29.Dd February 15, 2000
30.Dt SEM_POST 3
31.Os
32.Sh NAME
33.Nm sem_post
34.Nd increment (unlock) a semaphore
36.Sh LIBRARY
37.Lb libc
38.Sh SYNOPSIS
35.Sh SYNOPSIS
39.In semaphore.h
36.Fd #include <semaphore.h>
40.Ft int
41.Fn sem_post "sem_t *sem"
42.Sh DESCRIPTION
43The
44.Fn sem_post
45function increments (unlocks) the semaphore pointed to by
46.Fa sem .
47If there are threads blocked on the semaphore when
48.Fn sem_post
49is called, then the highest priority thread that has been blocked the longest on
50the semaphore will be allowed to return from
51.Fn sem_wait .
37.Ft int
38.Fn sem_post "sem_t *sem"
39.Sh DESCRIPTION
40The
41.Fn sem_post
42function increments (unlocks) the semaphore pointed to by
43.Fa sem .
44If there are threads blocked on the semaphore when
45.Fn sem_post
46is called, then the highest priority thread that has been blocked the longest on
47the semaphore will be allowed to return from
48.Fn sem_wait .
52.Pp
53The
54.Fn sem_post
55function is signal-reentrant and may be called within signal handlers.
56.Sh RETURN VALUES
49.Sh RETURN VALUES
57.Rv -std sem_post
50If successful,
51.Fn sem_post
52returns 0. Otherwise, -1 is returned and
53.Va errno
54is set to indicate the type of
55error.
58.Sh ERRORS
56.Sh ERRORS
59The
60.Fn sem_post
57.Fn sem_post
61function will fail if:
58will fail if:
62.Bl -tag -width Er
63.It Bq Er EINVAL
59.Bl -tag -width Er
60.It Bq Er EINVAL
64The
65.Fa sem
61.Fa sem
66argument
67points to an invalid semaphore.
68.El
69.Sh SEE ALSO
62points to an invalid semaphore.
63.El
64.Sh SEE ALSO
70.Xr sem_getvalue 3 ,
71.Xr sem_trywait 3 ,
72.Xr sem_wait 3 ,
65.Xr sem_wait 3 ,
73.Xr sem 4
66.Xr sem_trywait 3
74.Sh STANDARDS
67.Sh STANDARDS
75The
76.Fn sem_post
68.Fn sem_post
77function conforms to
78.St -p1003.1-96 .
69conforms to ISO/IEC 9945-1 ANSI/IEEE
70.Pq Dq Tn POSIX
71Std 1003.1 1996 Edition.