pthread_getattr_default_np - get or set default thread-creation attributes

NAME LIBRARY SYNOPSIS DESCRIPTION ERRORS ATTRIBUTES STANDARDS HISTORY EXAMPLES Program source SEE ALSO

NAME

pthread_getattr_default_np, pthread_setattr_default_np, − get or set default thread-creation attributes

LIBRARY

POSIX threads library (libpthread, −lpthread)

SYNOPSIS

#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <pthread.h>

int pthread_getattr_default_np(pthread_attr_t *attr);
int pthread_setattr_default_np(const pthread_attr_t *attr);

The pthread_setattr_default_np() function sets the default attributes used for creation of a new thread—that is, the attributes that are used when pthread_create(3) is called with a second argument that is NULL. The default attributes are set using the attributes supplied in *attr, a previously initialized thread attributes object. Note the following details about the supplied attributes object:

	•		The attribute settings in the object must be valid.
	•		The stack address attribute must not be set in the object.
	•		Setting the stack size attribute to zero means leave the default stack size unchanged.

The pthread_getattr_default_np() function initializes the thread attributes object referred to by attr so that it contains the default attributes used for thread creation.

ERRORS

	EINVAL		(pthread_setattr_default_np()) One of the attribute settings in attr is invalid, or the stack address attribute is set in attr.
	ENOMEM		(pthread_setattr_default_np()) Insufficient memory.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

STANDARDS

GNU; hence the suffix "_np" (nonportable) in their names.

HISTORY

glibc 2.18.

EXAMPLES

The program below uses pthread_getattr_default_np() to fetch the default thread-creation attributes and then displays various settings from the returned thread attributes object. When running the program, we see the following output:

$ ./a.out;
Stack size: 8388608
Guard size: 4096
Scheduling policy: SCHED_OTHER
Scheduling priority: 0
Detach state: JOINABLE
Inherit scheduler: INHERIT

Program source

#define _GNU_SOURCE
#include <err.h>
#include <pthread.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
static void
display_pthread_attr(pthread_attr_t *attr)
{
int s;
size_t stacksize;
size_t guardsize;
int policy;
struct sched_param schedparam;
int detachstate;
int inheritsched;
s = pthread_attr_getstacksize(attr, &stacksize);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getstacksize");
printf("Stack size: %zu\n", stacksize);
s = pthread_attr_getguardsize(attr, &guardsize);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getguardsize");
printf("Guard size: %zu\n", guardsize);
s = pthread_attr_getschedpolicy(attr, &policy);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getschedpolicy");
printf("Scheduling policy: %s\n",
(policy == SCHED_FIFO) ? "SCHED_FIFO" :
(policy == SCHED_RR) ? "SCHED_RR" :
(policy == SCHED_OTHER) ? "SCHED_OTHER" : "[unknown]");
s = pthread_attr_getschedparam(attr, &schedparam);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getschedparam");
printf("Scheduling priority: %d\n", schedparam.sched_priority);
s = pthread_attr_getdetachstate(attr, &detachstate);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getdetachstate");
printf("Detach state: %s\n",
(detachstate == PTHREAD_CREATE_DETACHED) ? "DETACHED" :
(detachstate == PTHREAD_CREATE_JOINABLE) ? "JOINABLE" :
"???");
s = pthread_attr_getinheritsched(attr, &inheritsched);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getinheritsched");
printf("Inherit scheduler: %s\n",
(inheritsched == PTHREAD_INHERIT_SCHED) ? "INHERIT" :
(inheritsched == PTHREAD_EXPLICIT_SCHED) ? "EXPLICIT" :
"???");
}
int
main(void)
{
int s;
pthread_attr_t attr;
s = pthread_getattr_default_np(&attr);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_getattr_default_np");
display_pthread_attr(&attr);
exit(EXIT_SUCCESS);
}