NAME
pthreadjoin - join with a terminated thread SYNOPSIS
#include
int pthreadjoin(pthreadt thread, void **retval); Compile and link with -pthread. DESCRIPTION The pthreadjoin() function waits for the thread specified by thread to terminate. If that thread has already terminated, then pthreadjoin() returns immediately. The thread specified by thread must be joinable. If retval is not NULL, then pthreadjoin() copies the exit status of the target thread (i.e., the value that the target thread supplied to pthreadexit(3)) into the location pointed to by *retval. If the tar‐ get thread was canceled, then PTHREADCANCELED is placed in *retval. If multiple threads simultaneously try to join with the same thread, the results are undefined. If the thread calling pthreadjoin() is canceled, then the target thread will remain joinable (i.e., it will not be detached). RETURN VALUE On success, pthreadjoin() 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. CONFORMING TO
POSIX.1-2001. NOTES After a successful call to pthreadjoin(), the caller is guaranteed that the target thread has terminated. Joining with a thread that has previously been joined results in unde‐ fined 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 functional‐ ity, 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. EXAMPLE See pthreadcreate(3). SEE ALSO pthreadcancel(3), pthreadcreate(3), pthreaddetach(3), pthreadexit(3), pthreadtryjoinnp(3), pthreads(7) COLOPHON
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Linux 2008-11-27 PTHREADJOIN(3)