1.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>. 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice(s), this list of conditions and the following disclaimer as 9.\" the first lines of this file unmodified other than the possible 10.\" addition of one or more copyright notices. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice(s), this list of conditions and the following disclaimer in 13.\" the documentation and/or other materials provided with the 14.\" distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 17.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE 20.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 23.\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 24.\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 25.\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 26.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27.\" 28.\" $FreeBSD: src/lib/libc_r/man/sem_post.3,v 1.1.2.8 2001/12/17 10:08:26 ru Exp $ 29.\" $DragonFly: src/lib/libc_r/man/sem_post.3,v 1.2 2003/06/17 04:26:48 dillon Exp $ 30.Dd April 15, 2009 31.Dt SEM_POST 3 32.Os 33.Sh NAME 34.Nm sem_post 35.Nd increment (unlock) a semaphore 36.Sh LIBRARY 37.Lb libpthread 38.Sh SYNOPSIS 39.In 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 . 52.Pp 53.Fn sem_post 54is signal-reentrant and may be called within signal handlers. 55.Sh RETURN VALUES 56.Rv -std sem_post 57.Sh ERRORS 58.Fn sem_post 59will fail if: 60.Bl -tag -width Er 61.It Bq Er EINVAL 62.Fa sem 63points to an invalid semaphore. 64.El 65.Sh SEE ALSO 66.Xr sem_trywait 3 , 67.Xr sem_wait 3 68.Sh STANDARDS 69.Fn sem_post 70conforms to 71.St -p1003.1-96 . 72