инициализировать и уничтожить объект атрибутов потока (initialize and destroy thread attributes object)
Имя (Name)
pthread_attr_init, pthread_attr_destroy - initialize and destroy
thread attributes object
Синопсис (Synopsis)
#include <pthread.h>
int pthread_attr_init(pthread_attr_t *attr);
int pthread_attr_destroy(pthread_attr_t *attr);
Compile and link with -pthread.
Описание (Description)
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.
Возвращаемое значение (Return value)
On success, these functions return 0; on error, they return a
nonzero error number.
Ошибки (Error)
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).
Атрибуты (Attributes)
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() │ │ │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008.
Примечание (Note)
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.
Примеры (Examples)
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 <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#define handle_error_en(en, msg) \
do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
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)
handle_error_en(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)
handle_error_en(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)
handle_error_en(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)
handle_error_en(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)
handle_error_en(s, "pthread_attr_getschedparam");
printf("%sScheduling priority = %d\n", prefix, sp.sched_priority);
s = pthread_attr_getguardsize(attr, &v);
if (s != 0)
handle_error_en(s, "pthread_attr_getguardsize");
printf("%sGuard size = %zu bytes\n", prefix, v);
s = pthread_attr_getstack(attr, &stkaddr, &v);
if (s != 0)
handle_error_en(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)
handle_error_en(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)
handle_error_en(s, "pthread_attr_init");
s = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
if (s != 0)
handle_error_en(s, "pthread_attr_setdetachstate");
s = pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
if (s != 0)
handle_error_en(s, "pthread_attr_setinheritsched");
stack_size = strtoul(argv[1], NULL, 0);
s = posix_memalign(&sp, sysconf(_SC_PAGESIZE), stack_size);
if (s != 0)
handle_error_en(s, "posix_memalign");
printf("posix_memalign() allocated at %p\n", sp);
s = pthread_attr_setstack(&attr, sp, stack_size);
if (s != 0)
handle_error_en(s, "pthread_attr_setstack");
}
s = pthread_create(&thr, attrp, &thread_start, NULL);
if (s != 0)
handle_error_en(s, "pthread_create");
if (attrp != NULL) {
s = pthread_attr_destroy(attrp);
if (s != 0)
handle_error_en(s, "pthread_attr_destroy");
}
pause(); /* Terminates when other thread calls exit() */
}
Смотри также (See also)
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)
