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glibc/nptl/pthread_join.c
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/* Copyright (C) 2002-2016 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, see | |
<http://www.gnu.org/licenses/>. */ | |
#include <errno.h> | |
#include <stdlib.h> | |
#include <atomic.h> | |
#include "pthreadP.h" | |
#include <stap-probe.h> | |
static void | |
cleanup (void *arg) | |
{ | |
/* If we already changed the waiter ID, reset it. The call cannot | |
fail for any reason but the thread not having done that yet so | |
there is no reason for a loop. */ | |
(void) atomic_compare_and_exchange_bool_acq ((struct pthread **) arg, NULL, | |
THREAD_SELF); | |
} | |
int | |
pthread_join (pthread_t threadid, void **thread_return) | |
{ | |
struct pthread *pd = (struct pthread *) threadid; | |
/* Make sure the descriptor is valid. */ | |
if (INVALID_NOT_TERMINATED_TD_P (pd)) | |
/* Not a valid thread handle. */ | |
return ESRCH; | |
/* Is the thread joinable?. */ | |
if (IS_DETACHED (pd)) | |
/* We cannot wait for the thread. */ | |
return EINVAL; | |
struct pthread *self = THREAD_SELF; | |
int result = 0; | |
LIBC_PROBE (pthread_join, 1, threadid); | |
/* During the wait we change to asynchronous cancellation. If we | |
are canceled the thread we are waiting for must be marked as | |
un-wait-ed for again. */ | |
pthread_cleanup_push (cleanup, &pd->joinid); | |
/* Switch to asynchronous cancellation. */ | |
int oldtype = CANCEL_ASYNC (); | |
if ((pd == self | |
|| (self->joinid == pd | |
&& (pd->cancelhandling | |
& (CANCELING_BITMASK | CANCELED_BITMASK | EXITING_BITMASK | |
| TERMINATED_BITMASK)) == 0)) | |
&& !CANCEL_ENABLED_AND_CANCELED (self->cancelhandling)) | |
/* This is a deadlock situation. The threads are waiting for each | |
other to finish. Note that this is a "may" error. To be 100% | |
sure we catch this error we would have to lock the data | |
structures but it is not necessary. In the unlikely case that | |
two threads are really caught in this situation they will | |
deadlock. It is the programmer's problem to figure this | |
out. */ | |
result = EDEADLK; | |
/* Wait for the thread to finish. If it is already locked something | |
is wrong. There can only be one waiter. */ | |
else if (__builtin_expect (atomic_compare_and_exchange_bool_acq (&pd->joinid, | |
self, | |
NULL), 0)) | |
/* There is already somebody waiting for the thread. */ | |
result = EINVAL; | |
else | |
/* Wait for the child. */ | |
lll_wait_tid (pd->tid); | |
/* Restore cancellation mode. */ | |
CANCEL_RESET (oldtype); | |
/* Remove the handler. */ | |
pthread_cleanup_pop (0); | |
if (__glibc_likely (result == 0)) | |
{ | |
/* We mark the thread as terminated and as joined. */ | |
pd->tid = -1; | |
/* Store the return value if the caller is interested. */ | |
if (thread_return != NULL) | |
*thread_return = pd->result; | |
/* Free the TCB. */ | |
__free_tcb (pd); | |
} | |
LIBC_PROBE (pthread_join_ret, 3, threadid, result, pd->result); | |
return result; | |
} |