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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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pthread_attr_init(3) Library Functions Manual pthread_attr_init(3)
pthread_attr_init, pthread_attr_destroy - initialize and destroy
thread attributes object
POSIX threads library (libpthread, -lpthread)
#include <pthread.h>
int pthread_attr_init(pthread_attr_t *attr);
int pthread_attr_destroy(pthread_attr_t *attr);
The pthread_attr_init() function initializes the thread
attributes object pointed to by attr with default attribute
values. After this call, individual attributes of the object can
be set using various related functions (listed under SEE ALSO),
and then the object can be used in one or more pthread_create(3)
calls that create threads.
Calling pthread_attr_init() on a thread attributes object that
has already been initialized results in undefined behavior.
When a thread attributes object is no longer required, it should
be destroyed using the pthread_attr_destroy() function.
Destroying a thread attributes object has no effect on threads
that were created using that object.
Once a thread attributes object has been destroyed, it can be
reinitialized using pthread_attr_init(). Any other use of a
destroyed thread attributes object has undefined results.
On success, these functions return 0; on error, they return a
nonzero error number.
POSIX.1 documents an ENOMEM error for pthread_attr_init(); on
Linux these functions always succeed (but portable and future-
proof applications should nevertheless handle a possible error
return).
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────────────────┼───────────────┼─────────┤
│ pthread_attr_init(), │ Thread safety │ MT-Safe │
│ pthread_attr_destroy() │ │ │
└─────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008.
POSIX.1-2001.
The pthread_attr_t type should be treated as opaque: any access
to the object other than via pthreads functions is nonportable
and produces undefined results.
The program below optionally makes use of pthread_attr_init() and
various related functions to initialize a thread attributes
object that is used to create a single thread. Once created, the
thread uses the pthread_getattr_np(3) function (a nonstandard GNU
extension) to retrieve the thread's attributes, and then displays
those attributes.
If the program is run with no command-line argument, then it
passes NULL as the attr argument of pthread_create(3), so that
the thread is created with default attributes. Running the
program on Linux/x86-32 with the NPTL threading implementation,
we see the following:
$ ulimit -s # No stack limit ==> default stack size is 2 MB
unlimited
$ ./a.out
Thread attributes:
Detach state = PTHREAD_CREATE_JOINABLE
Scope = PTHREAD_SCOPE_SYSTEM
Inherit scheduler = PTHREAD_INHERIT_SCHED
Scheduling policy = SCHED_OTHER
Scheduling priority = 0
Guard size = 4096 bytes
Stack address = 0x40196000
Stack size = 0x201000 bytes
When we supply a stack size as a command-line argument, the
program initializes a thread attributes object, sets various
attributes in that object, and passes a pointer to the object in
the call to pthread_create(3). Running the program on
Linux/x86-32 with the NPTL threading implementation, we see the
following:
$ ./a.out 0x3000000
posix_memalign() allocated at 0x40197000
Thread attributes:
Detach state = PTHREAD_CREATE_DETACHED
Scope = PTHREAD_SCOPE_SYSTEM
Inherit scheduler = PTHREAD_EXPLICIT_SCHED
Scheduling policy = SCHED_OTHER
Scheduling priority = 0
Guard size = 0 bytes
Stack address = 0x40197000
Stack size = 0x3000000 bytes
Program source
#define _GNU_SOURCE /* To get pthread_getattr_np() declaration */
#include <err.h>
#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
static void
display_pthread_attr(pthread_attr_t *attr, char *prefix)
{
int s, i;
size_t v;
void *stkaddr;
struct sched_param sp;
s = pthread_attr_getdetachstate(attr, &i);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getdetachstate");
printf("%sDetach state = %s\n", prefix,
(i == PTHREAD_CREATE_DETACHED) ? "PTHREAD_CREATE_DETACHED" :
(i == PTHREAD_CREATE_JOINABLE) ? "PTHREAD_CREATE_JOINABLE" :
"???");
s = pthread_attr_getscope(attr, &i);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getscope");
printf("%sScope = %s\n", prefix,
(i == PTHREAD_SCOPE_SYSTEM) ? "PTHREAD_SCOPE_SYSTEM" :
(i == PTHREAD_SCOPE_PROCESS) ? "PTHREAD_SCOPE_PROCESS" :
"???");
s = pthread_attr_getinheritsched(attr, &i);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getinheritsched");
printf("%sInherit scheduler = %s\n", prefix,
(i == PTHREAD_INHERIT_SCHED) ? "PTHREAD_INHERIT_SCHED" :
(i == PTHREAD_EXPLICIT_SCHED) ? "PTHREAD_EXPLICIT_SCHED" :
"???");
s = pthread_attr_getschedpolicy(attr, &i);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getschedpolicy");
printf("%sScheduling policy = %s\n", prefix,
(i == SCHED_OTHER) ? "SCHED_OTHER" :
(i == SCHED_FIFO) ? "SCHED_FIFO" :
(i == SCHED_RR) ? "SCHED_RR" :
"???");
s = pthread_attr_getschedparam(attr, &sp);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getschedparam");
printf("%sScheduling priority = %d\n", prefix, sp.sched_priority);
s = pthread_attr_getguardsize(attr, &v);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getguardsize");
printf("%sGuard size = %zu bytes\n", prefix, v);
s = pthread_attr_getstack(attr, &stkaddr, &v);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_getstack");
printf("%sStack address = %p\n", prefix, stkaddr);
printf("%sStack size = %#zx bytes\n", prefix, v);
}
static void *
thread_start(void *arg)
{
int s;
pthread_attr_t gattr;
/* pthread_getattr_np() is a non-standard GNU extension that
retrieves the attributes of the thread specified in its
first argument. */
s = pthread_getattr_np(pthread_self(), &gattr);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_getattr_np");
printf("Thread attributes:\n");
display_pthread_attr(&gattr, "\t");
exit(EXIT_SUCCESS); /* Terminate all threads */
}
int
main(int argc, char *argv[])
{
pthread_t thr;
pthread_attr_t attr;
pthread_attr_t *attrp; /* NULL or &attr */
int s;
attrp = NULL;
/* If a command-line argument was supplied, use it to set the
stack-size attribute and set a few other thread attributes,
and set attrp pointing to thread attributes object. */
if (argc > 1) {
size_t stack_size;
void *sp;
attrp = &attr;
s = pthread_attr_init(&attr);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_init");
s = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_setdetachstate");
s = pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_setinheritsched");
stack_size = strtoul(argv[1], NULL, 0);
s = posix_memalign(&sp, sysconf(_SC_PAGESIZE), stack_size);
if (s != 0)
errc(EXIT_FAILURE, s, "posix_memalign");
printf("posix_memalign() allocated at %p\n", sp);
s = pthread_attr_setstack(&attr, sp, stack_size);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_setstack");
}
s = pthread_create(&thr, attrp, &thread_start, NULL);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_create");
if (attrp != NULL) {
s = pthread_attr_destroy(attrp);
if (s != 0)
errc(EXIT_FAILURE, s, "pthread_attr_destroy");
}
pause(); /* Terminates when other thread calls exit() */
}
pthread_attr_setaffinity_np(3), pthread_attr_setdetachstate(3),
pthread_attr_setguardsize(3), pthread_attr_setinheritsched(3),
pthread_attr_setschedparam(3), pthread_attr_setschedpolicy(3),
pthread_attr_setscope(3), pthread_attr_setsigmask_np(3),
pthread_attr_setstack(3), pthread_attr_setstackaddr(3),
pthread_attr_setstacksize(3), pthread_create(3),
pthread_getattr_np(3), pthread_setattr_default_np(3), pthreads(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.9.1 2024-06-15 pthread_attr_init(3)
Pages that refer to this page: pthread_attr_setaffinity_np(3), pthread_attr_setdetachstate(3), pthread_attr_setguardsize(3), pthread_attr_setinheritsched(3), pthread_attr_setschedparam(3), pthread_attr_setschedpolicy(3), pthread_attr_setscope(3), pthread_attr_setsigmask_np(3), pthread_attr_setstack(3), pthread_attr_setstackaddr(3), pthread_attr_setstacksize(3), pthread_create(3), pthread_getattr_default_np(3), pthread_getattr_np(3), pthread_setschedparam(3), pthread_setschedprio(3), sigevent(3type), pthreads(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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