|Return to pthread_attr_getguardsize.3 CVS log||Up to [cvs.NetBSD.org] / src / lib / libpthread|
|File: [cvs.NetBSD.org] / src / lib / libpthread / pthread_attr_getguardsize.3 (download)
Revision 1.2, Thu Jul 8 18:24:34 2010 UTC (9 years, 8 months ago) by wiz
.\" $NetBSD: pthread_attr_getguardsize.3,v 1.2 2010/07/08 18:24:34 wiz Exp $ .\" .\" Copyright (c) 2010 Jukka Ruohonen <email@example.com> .\" 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, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``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 FOUNDATION OR CONTRIBUTORS .\" 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. .\" .Dd July 7, 2010 .Dt PTHREAD_ATTR_GETGUARDSIZE 3 .Os .Sh NAME .Nm pthread_attr_getguardsize .Nd get and set thread guard size .Sh LIBRARY .Lb libpthread .Sh SYNOPSIS .In pthread.h .Ft int .Fn pthread_attr_getguardsize \ "const pthread_attr_t * restrict attr" "size_t * restrict guardsize" .Ft int .Fn pthread_attr_setguardsize "pthread_attr_t *attr" "size_t guardsize" .Sh DESCRIPTION The .Fn pthread_attr_getguardsize and .Fn pthread_attr_setguardsize functions get and set .Fa guardsize in the .Fa attr object. If .Fa guardsize is larger than 0, the system reserves an additional region of guarded memory of at least .Fa guardsize bytes at the end of the thread's stack for each new thread created by using .Fa attr . .Pp The guarded area is understood to be pages of memory that are protected from read and write access. While the guarded area should be rounded by the system page size, the actual default size is implementation-defined. In .Nx the default .Fa guardsize is .Dv _SC_PAGESIZE , the system page size. .Pp The rationale behind .Fa guardsize is two-fold: .Bl -enum -offset 2n .It On the one hand, it provides protection against overflow of the stack pointer. If there is a guard area and a thread overflows its stack pointer into this extra memory area, it should receive a .Dv SIGSEGV signal or experience other comparable fatal error condition. Note that if a thread allocates large data structures on stack, it may be necessary to raise the default .Fa guardsize in order to detect stack overflows. .It On the other hand, the overflow protection may waste system resources if an application that creates a large number of threads knows that it will never overflow the stack. In this case it is possible to set .Fa guardsize to 0. .El .Pp If .Xr pthread_attr_setstack 3 or .Xr pthread_attr_setstackaddr 3 is used to set the stack address attribute in .Fa attr , the guard size attribute is ignored and no guard area will be allocated; it is the responsibility of the application to handle the overflow conditions. .Sh RETURN VALUES If successful, both functions return 0. Otherwise, an error number is returned to indicate the error. .Sh ERRORS No errors are defined for .Fn pthread_attr_getguardsize . .Pp The .Fn pthread_attr_setguardsize may fail if: .Bl -tag -width Er .It Bq Er ENOMEM There was insufficient memory. .El .Sh SEE ALSO .Xr pthread_attr 3 , .Xr pthread_attr_setstack 3 , .Xr sysconf 3 .Sh STANDARDS Both functions conform to .St -p1003.1-2008 .