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PTHREAD_JOIN(3) Linux Programmer's Manual PTHREAD_JOIN(3)
pthread_join - join with a terminated thread
#include <pthread.h>
int pthread_join(pthread_t thread, void **retval);
Compile and link with -pthread.
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).
On success, pthread_join() returns 0; on error, it returns an
error number.
EDEADLK
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.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│pthread_join() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2001, POSIX.1-2008.
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.
See pthread_create(3).
pthread_cancel(3), pthread_create(3), pthread_detach(3),
pthread_exit(3), pthread_tryjoin_np(3), pthreads(7)
This page is part of release 5.13 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
https://www.kernel.org/doc/man-pages/.
Linux 2021-03-22 PTHREAD_JOIN(3)
Pages that refer to this page: pthread_attr_setdetachstate(3), pthread_cancel(3), pthread_create(3), pthread_detach(3), pthread_exit(3), pthread_tryjoin_np(3)
Copyright and license for this manual page
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