pthread_join

- wait for thread termination

Synopsis

cc –mt [ flag... ] file... [ library... ]
#include <pthread.h>

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

Description

The pthread_join() function suspends processing of the calling thread until the target thread completes. thread must be a member of the current process and it cannot be a detached thread. See pthread_create(3C).

If two or more threads wait for the same thread to complete, all will suspend processing until the thread has terminated, and then one thread will return successfully and the others will return with an error of ESRCH. The pthread_join() function will not block processing of the calling thread if the target thread has already terminated.

If a pthread_join() call returns successfully with a non-null status argument, the value passed to pthread_exit(3C) by the terminating thread will be placed in the location referenced by status.

If the pthread_join() calling thread is cancelled, then the target thread will remain joinable by pthread_join(). However, the calling thread may set up a cancellation cleanup handler on thread prior to the join call, which may detach the target thread by calling pthread_detach(3C). See pthread_detach(3C) and pthread_cancel(3C).

Return Values

If successful, pthread_join() returns 0. Otherwise, an error number is returned to indicate the error.

Errors

EDEADLK

A joining deadlock would occur, such as when a thread attempts to wait for itself.

EINVAL

The thread corresponding to the given thread ID is a detached thread.

ESRCH

No thread could be found corresponding to the given thread ID.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

pthread_cancel(3C), pthread_create(3C), pthread_detach(3C), pthread_exit(3C), wait(3C), attributes(5), standards(5)

Notes

The pthread_join(3C) function must specify the thread ID for whose termination it will wait.

Calling pthread_join() also "detaches" the thread; that is, pthread_join() includes the effect of the pthread_detach() function. If a thread were to be cancelled when blocked in pthread_join(), an explicit detach would have to be performed in the cancellation cleanup handler. The pthread_detach() function exists primarily for this purpose.