Name
pthread_join — join with a terminated thread
Synopsis
#include <pthread.h>
int
pthread_join( |
pthread_t thread, |
void **retval); |
![[Note]](../stylesheet/note.png) |
Note |
|---|---|
|
Compile and link with |
DESCRIPTION
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).
ERRORS
- EDEADLK
-
A deadlock was detected (e.g., two threads tried to join with each other); or
threadspecifies the calling thread. - EINVAL
-
threadis not a joinable thread. - EINVAL
-
Another thread is already waiting to join with this thread.
- ESRCH
-
No thread with the ID
threadcould be found.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
pthread_join() |
Thread safety | MT-Safe |
NOTES
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 ALSO
pthread_cancel(3), pthread_create(3), pthread_detach(3), pthread_exit(3), pthread_tryjoin_np(3), pthreads(7)
COLOPHON
This page is part of release 5.11 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/.
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