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4735850f | 1 | /* Common definition for pthread_{timed,try}join{_np}. |
2b778ceb | 2 | Copyright (C) 2017-2021 Free Software Foundation, Inc. |
4735850f AZ |
3 | This file is part of the GNU C Library. |
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 | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
4735850f AZ |
18 | |
19 | #include "pthreadP.h" | |
20 | #include <atomic.h> | |
21 | #include <stap-probe.h> | |
48123656 | 22 | #include <time.h> |
4a14cb87 | 23 | #include <futex-internal.h> |
4735850f AZ |
24 | |
25 | static void | |
26 | cleanup (void *arg) | |
27 | { | |
28 | /* If we already changed the waiter ID, reset it. The call cannot | |
29 | fail for any reason but the thread not having done that yet so | |
30 | there is no reason for a loop. */ | |
31 | struct pthread *self = THREAD_SELF; | |
32 | atomic_compare_exchange_weak_acquire (&arg, &self, NULL); | |
33 | } | |
34 | ||
35 | int | |
69ca4b54 | 36 | __pthread_clockjoin_ex (pthread_t threadid, void **thread_return, |
4a14cb87 LM |
37 | clockid_t clockid, |
38 | const struct __timespec64 *abstime, bool block) | |
4735850f AZ |
39 | { |
40 | struct pthread *pd = (struct pthread *) threadid; | |
41 | ||
42 | /* Make sure the descriptor is valid. */ | |
43 | if (INVALID_NOT_TERMINATED_TD_P (pd)) | |
44 | /* Not a valid thread handle. */ | |
45 | return ESRCH; | |
46 | ||
47 | /* Is the thread joinable?. */ | |
48 | if (IS_DETACHED (pd)) | |
49 | /* We cannot wait for the thread. */ | |
50 | return EINVAL; | |
51 | ||
52 | struct pthread *self = THREAD_SELF; | |
53 | int result = 0; | |
54 | ||
55 | LIBC_PROBE (pthread_join, 1, threadid); | |
56 | ||
57 | if ((pd == self | |
58 | || (self->joinid == pd | |
59 | && (pd->cancelhandling | |
60 | & (CANCELING_BITMASK | CANCELED_BITMASK | EXITING_BITMASK | |
61 | | TERMINATED_BITMASK)) == 0)) | |
62 | && !CANCEL_ENABLED_AND_CANCELED (self->cancelhandling)) | |
63 | /* This is a deadlock situation. The threads are waiting for each | |
64 | other to finish. Note that this is a "may" error. To be 100% | |
65 | sure we catch this error we would have to lock the data | |
66 | structures but it is not necessary. In the unlikely case that | |
67 | two threads are really caught in this situation they will | |
68 | deadlock. It is the programmer's problem to figure this | |
69 | out. */ | |
70 | return EDEADLK; | |
71 | ||
72 | /* Wait for the thread to finish. If it is already locked something | |
73 | is wrong. There can only be one waiter. */ | |
74 | else if (__glibc_unlikely (atomic_compare_exchange_weak_acquire (&pd->joinid, | |
75 | &self, | |
76 | NULL))) | |
77 | /* There is already somebody waiting for the thread. */ | |
78 | return EINVAL; | |
79 | ||
eb76e5b4 AZ |
80 | /* BLOCK waits either indefinitely or based on an absolute time. POSIX also |
81 | states a cancellation point shall occur for pthread_join, and we use the | |
69ca4b54 | 82 | same rationale for posix_timedjoin_np. Both clockwait_tid and the futex |
eb76e5b4 | 83 | call use the cancellable variant. */ |
4735850f AZ |
84 | if (block) |
85 | { | |
86 | /* During the wait we change to asynchronous cancellation. If we | |
87 | are cancelled the thread we are waiting for must be marked as | |
88 | un-wait-ed for again. */ | |
89 | pthread_cleanup_push (cleanup, &pd->joinid); | |
90 | ||
9e92278f AZ |
91 | /* We need acquire MO here so that we synchronize with the |
92 | kernel's store to 0 when the clone terminates. (see above) */ | |
93 | pid_t tid; | |
94 | while ((tid = atomic_load_acquire (&pd->tid)) != 0) | |
95 | { | |
96 | /* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via | |
97 | futex wake-up when the clone terminates. The memory location | |
98 | contains the thread ID while the clone is running and is reset to | |
99 | zero by the kernel afterwards. The kernel up to version 3.16.3 | |
100 | does not use the private futex operations for futex wake-up when | |
101 | the clone terminates. */ | |
102 | int ret = __futex_abstimed_wait_cancelable64 ( | |
103 | (unsigned int *) &pd->tid, tid, clockid, abstime, LLL_SHARED); | |
104 | if (ret == ETIMEDOUT || ret == EOVERFLOW) | |
105 | { | |
106 | result = ret; | |
107 | break; | |
108 | } | |
eb76e5b4 | 109 | } |
4735850f AZ |
110 | |
111 | pthread_cleanup_pop (0); | |
112 | } | |
113 | ||
bc10e22c | 114 | void *pd_result = pd->result; |
4735850f AZ |
115 | if (__glibc_likely (result == 0)) |
116 | { | |
117 | /* We mark the thread as terminated and as joined. */ | |
118 | pd->tid = -1; | |
119 | ||
120 | /* Store the return value if the caller is interested. */ | |
121 | if (thread_return != NULL) | |
bc10e22c | 122 | *thread_return = pd_result; |
4735850f AZ |
123 | |
124 | /* Free the TCB. */ | |
125 | __free_tcb (pd); | |
126 | } | |
127 | else | |
128 | pd->joinid = NULL; | |
129 | ||
bc10e22c | 130 | LIBC_PROBE (pthread_join_ret, 3, threadid, result, pd_result); |
4735850f AZ |
131 | |
132 | return result; | |
133 | } |