Section: Linux Programmer's Manual (3)
pthread_join - join with a terminated thread
int pthread_join(pthread_t thread, void **retval);
Compile and link with -pthread.
function waits for the thread specified by
If that thread has already terminated, then
The thread specified by
must be joinable.
is not NULL, then
copies the exit status of the target thread
(i.e., the value that the target thread supplied to
into the location pointed to by
If the target thread was canceled, then
is placed in the location pointed to by
If multiple threads simultaneously try to join with the same thread,
the results are undefined.
If the thread calling
is canceled, then the target thread will remain joinable
(i.e., it will not be detached).
on error, it returns an error number.
A deadlock was detected
(e.g., two threads tried to join with each other);
specifies the calling thread.
is not a joinable thread.
Another thread is already waiting to join with this thread.
No thread with the ID
could be found.
For an explanation of the terms used in this section, see
After a successful call to
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
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.
This page is part of release 5.04 of the Linux
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