Section (3) pthread_attr_setguardsize
pthread_attr_setguardsize, pthread_attr_getguardsize — set/get guard size attribute in thread attributes object
||const pthread_attr_t *attr,|
Compile and link with
pthread_attr_setguardsize() function sets
the guard size attribute of the thread attributes object
referred to by
to the value specified in
greater than 0, then for each new thread created using
attr the system
allocates an additional region of at least
guardsize bytes at the end of
the thread_zsingle_quotesz_s stack to act as the guard area for the stack
(but see BUGS).
guardsize is 0,
then new threads created with
attr will not have a guard
The default guard size is the same as the system page size.
If the stack address attribute has been set in
attr (using pthread_attr_setstack(3) or
meaning that the caller is allocating the thread_zsingle_quotesz_s stack,
then the guard size attribute is ignored (i.e., no guard area
is created by the system): it is the application_zsingle_quotesz_s
responsibility to handle stack overflow (perhaps by using
mprotect(2) to manually
define a guard area at the end of the stack that it has
returns the guard size attribute of the thread attributes
object referred to by
attr in the buffer pointed to
POSIX.1 documents an EINVAL
guardsize is invalid.
On Linux these functions always succeed (but portable and
future-proof applications should nevertheless handle a
possible error return).
For an explanation of the terms used in this section, see attributes(7).
A guard area consists of virtual memory pages that are
protected to prevent read and write access. If a thread
overflows its stack into the guard area, then, on most hard
architectures, it receives a
SIGSEGV signal, thus notifying it of the
overflow. Guard areas start on page boundaries, and the guard
size is internally rounded up to the system page size when
creating a thread. (Nevertheless,
pthread_attr_getguardsize() returns the
guard size that was set by
Setting a guard size of 0 may be useful to save memory in an application that creates many threads and knows that stack overflow can never occur.
Choosing a guard size larger than the default size may be necessary for detecting stack overflows if a thread allocates large data structures on the stack.
As at glibc 2.8, the NPTL threading implementation includes the guard area within the stack size allocation, rather than allocating extra space at the end of the stack, as POSIX.1 requires. (This can result in an EINVAL error from pthread_create(3) if the guard size value is too large, leaving no space for the actual stack.)
The obsolete LinuxThreads implementation did the right thing, allocating extra space at the end of the stack for the guard area.
This page is part of release 4.16 of the Linux
man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date. The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein. The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.