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1 /*
2  * Copyright (C) 2008 The Android Open Source Project
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  *  * Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  *  * Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in
12  *    the documentation and/or other materials provided with the
13  *    distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #include <errno.h>
30 
31 #include "private/bionic_defs.h"
32 #include "private/bionic_futex.h"
33 #include "private/bionic_systrace.h"
34 #include "pthread_internal.h"
35 
36 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
pthread_join(pthread_t t,void ** return_value)37 int pthread_join(pthread_t t, void** return_value) {
38   ScopedTrace trace("pthread_join");
39   if (t == pthread_self()) {
40     return EDEADLK;
41   }
42 
43   pthread_internal_t* thread = __pthread_internal_find(t, "pthread_join");
44   if (thread == nullptr) {
45     return ESRCH;
46   }
47 
48   ThreadJoinState old_state = THREAD_NOT_JOINED;
49   while ((old_state == THREAD_NOT_JOINED || old_state == THREAD_EXITED_NOT_JOINED) &&
50          !atomic_compare_exchange_weak(&thread->join_state, &old_state, THREAD_JOINED)) {
51   }
52 
53   if (old_state == THREAD_DETACHED || old_state == THREAD_JOINED) {
54     return EINVAL;
55   }
56 
57   pid_t tid = thread->tid;
58   volatile int* tid_ptr = &thread->tid;
59 
60   // We set thread->join_state to THREAD_JOINED with atomic operation,
61   // so no one is going to remove this thread except us.
62 
63   // Wait for the thread to actually exit, if it hasn't already.
64   while (*tid_ptr != 0) {
65     __futex_wait(tid_ptr, tid, nullptr);
66   }
67 
68   if (return_value) {
69     *return_value = thread->return_value;
70   }
71 
72   __pthread_internal_remove_and_free(thread);
73   return 0;
74 }
75