pthread_join(3) — Linux manual page


PTHREAD_JOIN(3)           Linux Programmer's Manual          PTHREAD_JOIN(3)

NAME         top

       pthread_join - join with a terminated thread

SYNOPSIS         top

       #include <pthread.h>

       int pthread_join(pthread_t thread, void **retval);

       Compile and link with -pthread.

DESCRIPTION         top

       The pthread_join() function waits for the thread specified by thread
       to terminate.  If that thread has already terminated, then
       pthread_join() returns immediately.  The thread specified by thread
       must be joinable.

       If retval is not NULL, then pthread_join() copies the exit status of
       the target thread (i.e., the value that the target thread supplied to
       pthread_exit(3)) into the location pointed to by retval.  If the
       target thread was canceled, then PTHREAD_CANCELED is placed in the
       location pointed to by retval.

       If multiple threads simultaneously try to join with the same thread,
       the results are undefined.  If the thread calling pthread_join() is
       canceled, then the target thread will remain joinable (i.e., it will
       not be detached).

RETURN VALUE         top

       On success, pthread_join() returns 0; on error, it returns an error

ERRORS         top

              A deadlock was detected (e.g., two threads tried to join with
              each other); or thread specifies the calling thread.

       EINVAL thread is not a joinable thread.

       EINVAL Another thread is already waiting to join with this thread.

       ESRCH  No thread with the ID thread could be found.

ATTRIBUTES         top

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

       │Interface      Attribute     Value   │
       │pthread_join() │ Thread safety │ MT-Safe │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008.

NOTES         top

       After a successful call to pthread_join(), the caller is guaranteed
       that the target thread has terminated.  The caller may then choose to
       do any clean-up that is required after termination of the thread
       (e.g., freeing memory or other resources that were allocated to the
       target thread).

       Joining with a thread that has previously been joined results in
       undefined behavior.

       Failure to join with a thread that is joinable (i.e., one that is not
       detached), produces a "zombie thread".  Avoid doing this, since each
       zombie thread consumes some system resources, and when enough zombie
       threads have accumulated, it will no longer be possible to create new
       threads (or processes).

       There is no pthreads analog of waitpid(-1, &status, 0), that is,
       "join with any terminated thread".  If you believe you need this
       functionality, you probably need to rethink your application design.

       All of the threads in a process are peers: any thread can join with
       any other thread in the process.

EXAMPLES         top

       See pthread_create(3).

SEE ALSO         top

       pthread_cancel(3), pthread_create(3), pthread_detach(3),
       pthread_exit(3), pthread_tryjoin_np(3), pthreads(7)

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                            2020-06-09                  PTHREAD_JOIN(3)

Pages that refer to this page: pthread_attr_getdetachstate(3)pthread_attr_setdetachstate(3)pthread_cancel(3)pthread_create(3)pthread_detach(3)pthread_exit(3)pthread_timedjoin_np(3)pthread_tryjoin_np(3)