Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>.
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$FreeBSD$
.Dd February 15, 2000 .Dt SEM_POST 3 .Os .Sh NAME .Nm sem_post .Nd increment (unlock) a semaphore .Sh LIBRARY .Lb libc .Sh SYNOPSIS n semaphore.h .Ft int .Fn sem_post "sem_t *sem" .Sh DESCRIPTION The .Fn sem_post function increments (unlocks) the semaphore pointed to by .Fa sem . If there are threads blocked on the semaphore when .Fn sem_post is called, then the highest priority thread that has been blocked the longest on the semaphore will be allowed to return from .Fn sem_wait .
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice(s), this list of conditions and the following disclaimer as
the first lines of this file unmodified other than the possible
addition of one or more copyright notices.
2. Redistributions in binary form must reproduce the above copyright
notice(s), this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
$FreeBSD$
.Dd February 15, 2000 .Dt SEM_POST 3 .Os .Sh NAME .Nm sem_post .Nd increment (unlock) a semaphore .Sh LIBRARY .Lb libc .Sh SYNOPSIS n semaphore.h .Ft int .Fn sem_post "sem_t *sem" .Sh DESCRIPTION The .Fn sem_post function increments (unlocks) the semaphore pointed to by .Fa sem . If there are threads blocked on the semaphore when .Fn sem_post is called, then the highest priority thread that has been blocked the longest on the semaphore will be allowed to return from .Fn sem_wait .
p The .Fn sem_post function is signal-reentrant and may be called within signal handlers. .Sh RETURN VALUES .Rv -std sem_post .Sh ERRORS The .Fn sem_post function will fail if: l -tag -width Er t Bq Er EINVAL The .Fa sem argument points to an invalid semaphore. .El .Sh SEE ALSO .Xr sem_getvalue 3 , .Xr sem_trywait 3 , .Xr sem_wait 3 , .Xr sem 4 .Sh STANDARDS The .Fn sem_post function conforms to .St -p1003.1-96 .