1.\" Copyright (c) 2003 Sergey Osokin <osa@FreeBSD.org.ru> 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, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.Dd April 11, 2003 27.Dt PTHREAD_GETCONCURRENCY 3 28.Os 29.Sh NAME 30.Nm pthread_getconcurrency , 31.Nm pthread_setconcurrency 32.Nd get or set level of concurrency 33.Sh LIBRARY 34.Lb libpthread 35.Sh SYNOPSIS 36.In pthread.h 37.Ft int 38.Fn pthread_getconcurrency void 39.Ft int 40.Fn pthread_setconcurrency "int new_level" 41.Sh DESCRIPTION 42The 43.Fn pthread_getconcurrency 44function allows an application to inform the threads implementation 45of its desired concurrency level, 46.Fa new_level . 47The actual level of concurrency provided by the implementation 48as a result of this function call is unspecified. 49If 50.Fa new_level 51is zero, it causes the implementation to maintain the concurrency 52level at its discretion as if 53.Fn pthread_setconcurrency 54was never called. 55The 56.Fn pthread_getconcurrency 57function returns the value set by a previous call to the 58.Fn pthread_setconcurrency 59function. 60If the 61.Fn pthread_setconcurrency 62function was not previously called, this function returns zero to 63indicate that the implementation is maintaining the concurrency 64level. 65When an application calls 66.Fn pthread_setconcurrency , 67it is informing the implementation of its desired concurrency 68level. 69The implementation uses this as a hint, not a requirement. 70.Sh RETURN VALUES 71If successful, the 72.Fn pthread_setconcurrency 73function returns zero. 74Otherwise, an error number is returned 75to indicate the error. 76The 77.Fn pthread_getconcurrency 78function always returns the concurrency level set by a previous 79call to 80.Fn pthread_setconcurrency . 81If the 82.Fn pthread_setconcurrency 83function has never been called, 84.Fn pthread_getconcurrency 85returns zero. 86.Sh ERRORS 87The 88.Fn pthread_setconcurrency 89function will fail if: 90.Bl -tag -width Er 91.It Bq Er EINVAL 92The value specified by 93.Fa new_level 94is negative. 95.It Bq Er EAGAIN 96The value specified by 97.Fa new_level 98would cause a system resource to be exceeded. 99.El 100.Sh APPLICATION USAGE 101Use of these functions changes the state of the underlying 102concurrency upon which the application depends. 103Library developers are advised to not use the 104.Fn pthread_getconcurrency 105and 106.Fn pthread_setconcurrency 107functions since their use may conflict with an application's 108use of these functions. 109.Sh STANDARDS 110The 111.Fn pthread_getconcurrency 112and 113.Fn pthread_setconcurrency 114functions conform to 115.St -susv2 . 116