PTHREAD_JOIN
Section: Linux Programmer's Manual (3)
Updated: 2021-03-22
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NAME
pthread_join - join with a terminated thread
SYNOPSIS
#include <pthread.h>
int pthread_join(pthread_t thread, void **retval);
Compile and link with -pthread.
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).
RETURN VALUE
On success,
pthread_join()
returns 0;
on error, it returns an error number.
ERRORS
- 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.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
pthread_join()
| Thread safety | MT-Safe
|
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
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.
EXAMPLES
See
pthread_create(3).
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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- EXAMPLES
-
- SEE ALSO
-
- COLOPHON
-
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Time: 06:22:47 GMT, May 09, 2021