Originální popis anglicky:
pthread_attr_getguardsize, pthread_attr_setguardsize - get and set the thread
guardsize attribute
Návod, kniha: POSIX Programmer's Manual
#include <pthread.h>
int pthread_attr_getguardsize(const pthread_attr_t *restrict
attr,
size_t *restrict
guardsize );
int pthread_attr_setguardsize(pthread_attr_t
*attr,
size_t
guardsize);
The
pthread_attr_getguardsize() function shall get the
guardsize
attribute in the
attr object. This attribute shall be returned in the
guardsize parameter.
The
pthread_attr_setguardsize() function shall set the
guardsize
attribute in the
attr object. The new value of this attribute shall be
obtained from the
guardsize parameter. If
guardsize is zero, a
guard area shall not be provided for threads created with
attr. If
guardsize is greater than zero, a guard area of at least size
guardsize bytes shall be provided for each thread created with
attr.
The
guardsize attribute controls the size of the guard area for the
created thread's stack. The
guardsize attribute provides protection
against overflow of the stack pointer. If a thread's stack is created with
guard protection, the implementation allocates extra memory at the overflow
end of the stack as a buffer against stack overflow of the stack pointer. If
an application overflows into this buffer an error shall result (possibly in a
SIGSEGV signal being delivered to the thread).
A conforming implementation may round up the value contained in
guardsize
to a multiple of the configurable system variable {PAGESIZE} (see
<sys/mman.h>). If an implementation rounds up the value of
guardsize to a multiple of {PAGESIZE}, a call to
pthread_attr_getguardsize() specifying
attr shall store in the
guardsize parameter the guard size specified by the previous
pthread_attr_setguardsize() function call.
The default value of the
guardsize attribute is {PAGESIZE} bytes. The
actual value of {PAGESIZE} is implementation-defined.
If the
stackaddr or
stack attribute has been set (that is, the
caller is allocating and managing its own thread stacks), the
guardsize
attribute shall be ignored and no protection shall be provided by the
implementation. It is the responsibility of the application to manage stack
overflow along with stack allocation and management in this case.
If successful, the
pthread_attr_getguardsize() and
pthread_attr_setguardsize() functions shall return zero; otherwise, an
error number shall be returned to indicate the error.
The
pthread_attr_getguardsize() and
pthread_attr_setguardsize()
functions shall fail if:
- EINVAL
- The attribute attr is invalid.
- EINVAL
- The parameter guardsize is invalid.
These functions shall not return an error code of [EINTR].
The following sections are informative.
None.
None.
The
guardsize attribute is provided to the application for two reasons:
- 1.
- Overflow protection can potentially result in wasted system
resources. An application that creates a large number of threads, and
which knows its threads never overflow their stack, can save system
resources by turning off guard areas.
- 2.
- When threads allocate large data structures on the stack,
large guard areas may be needed to detect stack overflow.
None.
The Base Definitions volume of IEEE Std 1003.1-2001,
<pthread.h>,
<sys/mman.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
