pthread_attr_init(3) - Linux manual page (original) (raw)
pthreadattrinit(3) Library Functions Manual pthreadattrinit(3)
NAME top
pthread_attr_init, pthread_attr_destroy - initialize and destroy
thread attributes objectLIBRARY top
POSIX threads library (_libpthread_, _-lpthread_)SYNOPSIS top
**#include <pthread.h>**
**int pthread_attr_init(pthread_attr_t ***_attr_**);**
**int pthread_attr_destroy(pthread_attr_t ***_attr_**);**DESCRIPTION top
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)](../man3/pthread%5Fcreate.3.html) 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.RETURN VALUE top
On success, these functions return 0; on error, they return a
nonzero error number.ERRORS top
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).ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **pthread_attr_init**(), │ Thread safety │ MT-Safe │
│ **pthread_attr_destroy**() │ │ │
└──────────────────────────────────────┴───────────────┴─────────┘STANDARDS top
POSIX.1-2008.HISTORY top
POSIX.1-2001.NOTES top
The _pthreadattrt_ type should be treated as opaque: any access to
the object other than via pthreads functions is nonportable and
produces undefined results.EXAMPLES top
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)](../man3/pthread%5Fgetattr%5Fnp.3.html) 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)](../man3/pthread%5Fcreate.3.html), 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)](../man3/pthread%5Fcreate.3.html). 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 bytesProgram 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() */
}SEE ALSO top
[pthread_attr_setaffinity_np(3)](../man3/pthread%5Fattr%5Fsetaffinity%5Fnp.3.html), [pthread_attr_setdetachstate(3)](../man3/pthread%5Fattr%5Fsetdetachstate.3.html),
[pthread_attr_setguardsize(3)](../man3/pthread%5Fattr%5Fsetguardsize.3.html), [pthread_attr_setinheritsched(3)](../man3/pthread%5Fattr%5Fsetinheritsched.3.html),
[pthread_attr_setschedparam(3)](../man3/pthread%5Fattr%5Fsetschedparam.3.html), [pthread_attr_setschedpolicy(3)](../man3/pthread%5Fattr%5Fsetschedpolicy.3.html),
[pthread_attr_setscope(3)](../man3/pthread%5Fattr%5Fsetscope.3.html), [pthread_attr_setsigmask_np(3)](../man3/pthread%5Fattr%5Fsetsigmask%5Fnp.3.html),
[pthread_attr_setstack(3)](../man3/pthread%5Fattr%5Fsetstack.3.html), [pthread_attr_setstackaddr(3)](../man3/pthread%5Fattr%5Fsetstackaddr.3.html),
[pthread_attr_setstacksize(3)](../man3/pthread%5Fattr%5Fsetstacksize.3.html), [pthread_create(3)](../man3/pthread%5Fcreate.3.html),
[pthread_getattr_np(3)](../man3/pthread%5Fgetattr%5Fnp.3.html), [pthread_setattr_default_np(3)](../man3/pthread%5Fsetattr%5Fdefault%5Fnp.3.html), [pthreads(7)](../man7/pthreads.7.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 pthreadattrinit(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)