Linux cli command pthread_getattr_default_np

NAME 🖥️ pthread_getattr_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);

DESCRIPTION

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 <errno.h>
#include <pthread.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

“, stacksize); s = pthread_attr_getguardsize(attr, &guardsize); if (s != 0) errc(EXIT_FAILURE, s, “pthread_attr_getguardsize”); printf(“Guard size: %zu “, guardsize); s = pthread_attr_getschedpolicy(attr, &policy); if (s != 0) errc(EXIT_FAILURE, s, “pthread_attr_getschedpolicy”); printf(“Scheduling policy: %s “, (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 “, schedparam.sched_priority); s = pthread_attr_getdetachstate(attr, &detachstate); if (s != 0) errc(EXIT_FAILURE, s, “pthread_attr_getdetachstate”); printf(“Detach state: %s “, (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 “, (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); }

SEE ALSO

pthread_attr_getaffinity_np(3), pthread_attr_getdetachstate(3), pthread_attr_getguardsize(3), pthread_attr_getinheritsched(3), pthread_attr_getschedparam(3), pthread_attr_getschedpolicy(3), pthread_attr_getscope(3), pthread_attr_getstack(3), pthread_attr_getstackaddr(3), pthread_attr_getstacksize(3), pthread_attr_init(3), pthread_create(3), pthreads(7)

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