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.TH PTHREAD_GETATTR_DEFAULT_NP 3 2017-09-15 "Linux" "Linux Programmer's Manual"

.SH NAME

pthread_getattr_default_np, pthread_setattr_default_np, \-

get or set default thread-creation attributes

.SH SYNOPSIS

.nf

.BR "#define _GNU_SOURCE" "             /* See feature_test_macros(7) */"

.B #include <pthread.h>

.PP

.BI "int pthread_getattr_default_np(pthread_attr_t *" attr );

.BI "int pthread_setattr_default_np(pthread_attr_t *" attr );

.PP

Compile and link with \fI\-pthread\fP.

.fi

.SH DESCRIPTION

The

.BR pthread_setattr_default_np ()

function sets the default attributes used for creation of a new

thread\(emthat is, the attributes that are used when

.BR pthread_create (3)

is called with a second argument that is NULL.

The default attributes are set using the attributes supplied in

.IR *attr ,

a previously initialized thread attributes object.

Note the following details about the supplied attributes object:

.IP * 3

The attribute settings in the object must be valid.

.IP *

The

.IR "stack address"

attribute must not be set in the object.

.IP *

Setting the

.IR "stack size"

attribute to zero means leave the default stack size unchanged.

.PP

The

.BR pthread_getattr_default_np ()

function initializes the thread attributes object referred to by

.I attr

so that it contains the default attributes used for thread creation.

.SH ERRORS

.TP

.B EINVAL

.RB ( pthread_setattr_default_np ())

One of the attribute settings in

.IR attr

is invalid, or the stack address attribute is set in

.IR attr .

.TP

.B ENOMEM

.\" Can happen (but unlikely) while trying to allocate memory for cpuset

.RB ( pthread_setattr_default_np ())

Insufficient memory.

.SH VERSIONS

These functions are available in glibc since version 2.18.

.SH ATTRIBUTES

For an explanation of the terms used in this section, see

.BR attributes (7).

.ad l

.TS

allbox;

lbw30 lb lb

l l l.

Interface	Attribute	Value

T{

.BR pthread_getattr_default_np (),

.BR pthread_setattr_default_np ()

T}	Thread safety	MT-Safe

.TE

.ad

.SH CONFORMING TO

These functions are nonstandard GNU extensions;

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

.SH EXAMPLE

The program below uses

.BR 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:

.PP

.in +4n

.EX

$ \fB./a.out\fP

Stack size:          8388608

Guard size:          4096

Scheduling policy:   SCHED_OTHER

Scheduling priority: 0

Detach state:        JOINABLE

Inherit scheduler:   INHERIT

.EE

.in

.PP

.SS Program source

\&

.EX

#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);

}

.EE

.SH SEE ALSO

.ad l

.nh

.BR pthread_attr_getaffinity_np (3),

.BR pthread_attr_getdetachstate (3),

.BR pthread_attr_getguardsize (3),

.BR pthread_attr_getinheritsched (3),

.BR pthread_attr_getschedparam (3),

.BR pthread_attr_getschedpolicy (3),

.BR pthread_attr_getscope (3),

.BR pthread_attr_getstack (3),

.BR pthread_attr_getstackaddr (3),

.BR pthread_attr_getstacksize (3),

.BR pthread_attr_init (3),

.BR pthread_create (3),

.BR pthreads (7)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.