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114 lines
3.6 KiB
Groff
114 lines
3.6 KiB
Groff
.\" Copyright (c) 2003 Sergey Osokin <osa@FreeBSD.org.ru>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.Dd April 11, 2003
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.Dt PTHREAD_GETCONCURRENCY 3
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.Os
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.Sh NAME
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.Nm pthread_getconcurrency ,
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.Nm pthread_setconcurrency
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.Nd get or set level of concurrency
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.Sh LIBRARY
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.Lb libpthread
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.Sh SYNOPSIS
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.In pthread.h
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.Ft int
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.Fn pthread_getconcurrency void
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.Ft int
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.Fn pthread_setconcurrency "int new_level"
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.Sh DESCRIPTION
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The
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.Fn pthread_setconcurrency
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function allows an application to inform the threads implementation
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of its desired concurrency level,
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.Fa new_level .
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The actual level of concurrency provided by the implementation
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as a result of this function call is unspecified.
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If
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.Fa new_level
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is zero, it causes the implementation to maintain the concurrency
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level at its discretion as if
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.Fn pthread_setconcurrency
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was never called.
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The
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.Fn pthread_getconcurrency
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function returns the value set by a previous call to the
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.Fn pthread_setconcurrency
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function.
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If the
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.Fn pthread_setconcurrency
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function was not previously called, this function returns zero to
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indicate that the implementation is maintaining the concurrency
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level.
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When an application calls
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.Fn pthread_setconcurrency ,
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it is informing the implementation of its desired concurrency
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level.
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The implementation uses this as a hint, not a requirement.
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.Sh RETURN VALUES
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If successful, the
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.Fn pthread_setconcurrency
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function returns zero.
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Otherwise, an error number is returned
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to indicate the error.
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The
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.Fn pthread_getconcurrency
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function always returns the concurrency level set by a previous
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call to
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.Fn pthread_setconcurrency .
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If the
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.Fn pthread_setconcurrency
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function has never been called,
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.Fn pthread_getconcurrency
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returns zero.
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.Sh ERRORS
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The
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.Fn pthread_setconcurrency
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The value specified by
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.Fa new_level
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is negative.
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.It Bq Er EAGAIN
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The value specified by
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.Fa new_level
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would cause a system resource to be exceeded.
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.El
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.Sh APPLICATION USAGE
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Use of these functions changes the state of the underlying
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concurrency upon which the application depends.
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Library developers are advised to not use the
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.Fn pthread_getconcurrency
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and
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.Fn pthread_setconcurrency
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functions since their use may conflict with an application's
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use of these functions.
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.Sh STANDARDS
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The
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.Fn pthread_getconcurrency
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and
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.Fn pthread_setconcurrency
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functions conform to
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.St -susv2 .
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