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 | |
28 | static void |
29 | cleanup (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 | |
39 | int |
40 | pthread_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 | |