PTHREAD_GETATTR_DEFAULT_NP

Section: Linux Programmer's Manual (3)
Updated: 2020-06-09
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NAME

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

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(pthread_attr_t *attr);

Compile and link with -pthread.

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.

VERSIONS

These functions are available in glibc since version 2.18.

ATTRIBUTES

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

Interface	Attribute	Value
pthread_getattr_default_np(), pthread_setattr_default_np()	Thread safety	MT-Safe

CONFORMING TO

These functions are nonstandard GNU extensions; hence the suffix "_np" (nonportable) in their names.

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 <pthread.h> #include <stdio.h> #include <stdlib.h> #include <errno.h>

#define errExitEN(en, msg) \
do { errno = en; perror(msg); \
exit(EXIT_FAILURE); } while (0)

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)
        errExitEN(s, "pthread_attr_getstacksize");
    printf("Stack size:          %zd\n", stacksize);

    s = pthread_attr_getguardsize(attr, &guardsize);
    if (s != 0)
        errExitEN(s, "pthread_attr_getguardsize");
    printf("Guard size:          %zd\n", guardsize);

    s = pthread_attr_getschedpolicy(attr, &policy);
    if (s != 0)
        errExitEN(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)
        errExitEN(s, "pthread_attr_getschedparam");
    printf("Scheduling priority: %d\n", schedparam.sched_priority);

    s = pthread_attr_getdetachstate(attr, &detachstate);
    if (s != 0)
        errExitEN(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)
        errExitEN(s, "pthread_attr_getinheritsched");
    printf("Inherit scheduler:   %s\n",
            (inheritsched == PTHREAD_INHERIT_SCHED) ? "INHERIT" :
            (inheritsched == PTHREAD_EXPLICIT_SCHED) ? "EXPLICIT" :
            "???"); }

int main(int argc, char *argv[]) {
int s;
pthread_attr_t attr;

    s = pthread_getattr_default_np(&attr);
    if (s != 0)
        errExitEN(s, "pthread_getattr_default_np");

display_pthread_attr(&attr);

exit(EXIT_SUCCESS); }

COLOPHON

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