1/* Copyright (C) 2002-2016 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#include <errno.h>
20#include <stdlib.h>
21
22#include <atomic.h>
23#include "pthreadP.h"
24
25#include <stap-probe.h>
26
27
28static void
29cleanup (void *arg)
30{
31 /* If we already changed the waiter ID, reset it. The call cannot
32 fail for any reason but the thread not having done that yet so
33 there is no reason for a loop. */
34 (void) atomic_compare_and_exchange_bool_acq ((struct pthread **) arg, NULL,
35 THREAD_SELF);
36}
37
38
39int
40pthread_join (pthread_t threadid, void **thread_return)
41{
42 struct pthread *pd = (struct pthread *) threadid;
43
44 /* Make sure the descriptor is valid. */
45 if (INVALID_NOT_TERMINATED_TD_P (pd))
46 /* Not a valid thread handle. */
47 return ESRCH;
48
49 /* Is the thread joinable?. */
50 if (IS_DETACHED (pd))
51 /* We cannot wait for the thread. */
52 return EINVAL;
53
54 struct pthread *self = THREAD_SELF;
55 int result = 0;
56
57 LIBC_PROBE (pthread_join, 1, threadid);
58
59 /* During the wait we change to asynchronous cancellation. If we
60 are canceled the thread we are waiting for must be marked as
61 un-wait-ed for again. */
62 pthread_cleanup_push (cleanup, &pd->joinid);
63
64 /* Switch to asynchronous cancellation. */
65 int oldtype = CANCEL_ASYNC ();
66
67 if ((pd == self
68 || (self->joinid == pd
69 && (pd->cancelhandling
70 & (CANCELING_BITMASK | CANCELED_BITMASK | EXITING_BITMASK
71 | TERMINATED_BITMASK)) == 0))
72 && !CANCEL_ENABLED_AND_CANCELED (self->cancelhandling))
73 /* This is a deadlock situation. The threads are waiting for each
74 other to finish. Note that this is a "may" error. To be 100%
75 sure we catch this error we would have to lock the data
76 structures but it is not necessary. In the unlikely case that
77 two threads are really caught in this situation they will
78 deadlock. It is the programmer's problem to figure this
79 out. */
80 result = EDEADLK;
81 /* Wait for the thread to finish. If it is already locked something
82 is wrong. There can only be one waiter. */
83 else if (__builtin_expect (atomic_compare_and_exchange_bool_acq (&pd->joinid,
84 self,
85 NULL), 0))
86 /* There is already somebody waiting for the thread. */
87 result = EINVAL;
88 else
89 /* Wait for the child. */
90 lll_wait_tid (pd->tid);
91
92
93 /* Restore cancellation mode. */
94 CANCEL_RESET (oldtype);
95
96 /* Remove the handler. */
97 pthread_cleanup_pop (0);
98
99
100 if (__glibc_likely (result == 0))
101 {
102 /* We mark the thread as terminated and as joined. */
103 pd->tid = -1;
104
105 /* Store the return value if the caller is interested. */
106 if (thread_return != NULL)
107 *thread_return = pd->result;
108
109
110 /* Free the TCB. */
111 __free_tcb (pd);
112 }
113
114 LIBC_PROBE (pthread_join_ret, 3, threadid, result, pd->result);
115
116 return result;
117}
118