pthread_getattr_np (3) - Linux Manuals
pthread_getattr_np: get attributes of created thread
NAME
pthread_getattr_np - get attributes of created thread
SYNOPSIS
#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <pthread.h> int pthread_getattr_np(pthread_t thread, pthread_attr_t *attr); Compile and link with -pthread.
DESCRIPTION
The pthread_getattr_np() function initializes the thread attributes object referred to by attr so that it contains actual attribute values describing the running thread thread.The returned attribute values may differ from the corresponding attribute values passed in the attr object that was used to create the thread using pthread_create(3). In particular, the following attributes may differ:
- *
- the detach state, since a joinable thread may have detached itself after creation;
- *
- the stack size, which the implementation may align to a suitable boundary.
- *
- and the guard size, which the implementation may round upward to a multiple of the page size, or ignore (i.e., treat as 0), if the application is allocating its own stack.
Furthermore, if the stack address attribute was not set in the thread attributes object used to create the thread, then the returned thread attributes object will report the actual stack address that the implementation selected for the thread.
When the thread attributes object returned by pthread_getattr_np() is no longer required, it should be destroyed using pthread_attr_destroy(3).
RETURN VALUE
On success, this function returns 0; on error, it returns a nonzero error number.ERRORS
- ENOMEM
- Insufficient memory.
In addition, if thread refers to the main thread, then pthread_getattr_np() can fail because of errors from various underlying calls: fopen(3), if /proc/self/maps can't be opened; and getrlimit(2), if the RLIMIT_STACK resource limit is not supported.
VERSIONS
This function is available in glibc since version 2.2.3.ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).Interface | Attribute | Value |
pthread_getattr_np() | Thread safety | MT-Safe |
CONFORMING TO
This function is a nonstandard GNU extension; hence the suffix "_np" (nonportable) in the name.EXAMPLES
The program below demonstrates the use of pthread_getattr_np(). The program creates a thread that then uses pthread_getattr_np() to retrieve and display its guard size, stack address, and stack size attributes. Command-line arguments can be used to set these attributes to values other than the default when creating the thread. The shell sessions below demonstrate the use of the program.In the first run, on an x86-32 system, a thread is created using default attributes:
$ ulimit -s # No stack limit ==> default stack size is 2 MB
unlimited
$ ./a.out
Attributes of created thread:
In the following run, we see that if a guard size is specified,
it is rounded up to the next multiple of the system page size
(4096 bytes on x86-32):
$ ./a.out -g 4097
Thread attributes object after initializations:
Attributes of created thread:
In the last run, the program manually allocates a stack for the thread.
In this case, the guard size attribute is ignored.
$ ./a.out -g 4096 -s 0x8000 -a
Allocated thread stack at 0x804d000
Thread attributes object after initializations:
Attributes of created thread:
#define handle_error_en(en, msg) \
static void
display_stack_related_attributes(pthread_attr_t *attr, char *prefix)
{
Program source
#define _GNU_SOURCE /* To get pthread_getattr_np() declaration */
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>