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4735850f | 1 | /* Common definition for pthread_{timed,try}join{_np}. |
d614a753 | 2 | Copyright (C) 2017-2020 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> |
4735850f AZ |
23 | |
24 | static void | |
25 | cleanup (void *arg) | |
26 | { | |
27 | /* If we already changed the waiter ID, reset it. The call cannot | |
28 | fail for any reason but the thread not having done that yet so | |
29 | there is no reason for a loop. */ | |
30 | struct pthread *self = THREAD_SELF; | |
31 | atomic_compare_exchange_weak_acquire (&arg, &self, NULL); | |
32 | } | |
33 | ||
eb76e5b4 AZ |
34 | /* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via futex |
35 | wake-up when the clone terminates. The memory location contains the | |
36 | thread ID while the clone is running and is reset to zero by the kernel | |
37 | afterwards. The kernel up to version 3.16.3 does not use the private futex | |
38 | operations for futex wake-up when the clone terminates. */ | |
39 | static int | |
69ca4b54 | 40 | clockwait_tid (pid_t *tidp, clockid_t clockid, const struct timespec *abstime) |
eb76e5b4 AZ |
41 | { |
42 | pid_t tid; | |
43 | ||
48123656 | 44 | if (! valid_nanoseconds (abstime->tv_nsec)) |
eb76e5b4 AZ |
45 | return EINVAL; |
46 | ||
47 | /* Repeat until thread terminated. */ | |
48 | while ((tid = *tidp) != 0) | |
49 | { | |
eb76e5b4 AZ |
50 | struct timespec rt; |
51 | ||
69ca4b54 MC |
52 | /* Get the current time. This can only fail if clockid is |
53 | invalid. */ | |
54 | if (__glibc_unlikely (__clock_gettime (clockid, &rt))) | |
55 | return EINVAL; | |
eb76e5b4 AZ |
56 | |
57 | /* Compute relative timeout. */ | |
4a39c34c ZW |
58 | rt.tv_sec = abstime->tv_sec - rt.tv_sec; |
59 | rt.tv_nsec = abstime->tv_nsec - rt.tv_nsec; | |
eb76e5b4 AZ |
60 | if (rt.tv_nsec < 0) |
61 | { | |
62 | rt.tv_nsec += 1000000000; | |
63 | --rt.tv_sec; | |
64 | } | |
65 | ||
66 | /* Already timed out? */ | |
67 | if (rt.tv_sec < 0) | |
68 | return ETIMEDOUT; | |
69 | ||
70 | /* If *tidp == tid, wait until thread terminates or the wait times out. | |
71 | The kernel up to version 3.16.3 does not use the private futex | |
72 | operations for futex wake-up when the clone terminates. */ | |
73 | if (lll_futex_timed_wait_cancel (tidp, tid, &rt, LLL_SHARED) | |
74 | == -ETIMEDOUT) | |
75 | return ETIMEDOUT; | |
76 | } | |
77 | ||
78 | return 0; | |
79 | } | |
80 | ||
4735850f | 81 | int |
69ca4b54 MC |
82 | __pthread_clockjoin_ex (pthread_t threadid, void **thread_return, |
83 | clockid_t clockid, | |
4735850f AZ |
84 | const struct timespec *abstime, bool block) |
85 | { | |
86 | struct pthread *pd = (struct pthread *) threadid; | |
87 | ||
88 | /* Make sure the descriptor is valid. */ | |
89 | if (INVALID_NOT_TERMINATED_TD_P (pd)) | |
90 | /* Not a valid thread handle. */ | |
91 | return ESRCH; | |
92 | ||
93 | /* Is the thread joinable?. */ | |
94 | if (IS_DETACHED (pd)) | |
95 | /* We cannot wait for the thread. */ | |
96 | return EINVAL; | |
97 | ||
98 | struct pthread *self = THREAD_SELF; | |
99 | int result = 0; | |
100 | ||
101 | LIBC_PROBE (pthread_join, 1, threadid); | |
102 | ||
103 | if ((pd == self | |
104 | || (self->joinid == pd | |
105 | && (pd->cancelhandling | |
106 | & (CANCELING_BITMASK | CANCELED_BITMASK | EXITING_BITMASK | |
107 | | TERMINATED_BITMASK)) == 0)) | |
108 | && !CANCEL_ENABLED_AND_CANCELED (self->cancelhandling)) | |
109 | /* This is a deadlock situation. The threads are waiting for each | |
110 | other to finish. Note that this is a "may" error. To be 100% | |
111 | sure we catch this error we would have to lock the data | |
112 | structures but it is not necessary. In the unlikely case that | |
113 | two threads are really caught in this situation they will | |
114 | deadlock. It is the programmer's problem to figure this | |
115 | out. */ | |
116 | return EDEADLK; | |
117 | ||
118 | /* Wait for the thread to finish. If it is already locked something | |
119 | is wrong. There can only be one waiter. */ | |
120 | else if (__glibc_unlikely (atomic_compare_exchange_weak_acquire (&pd->joinid, | |
121 | &self, | |
122 | NULL))) | |
123 | /* There is already somebody waiting for the thread. */ | |
124 | return EINVAL; | |
125 | ||
eb76e5b4 AZ |
126 | /* BLOCK waits either indefinitely or based on an absolute time. POSIX also |
127 | states a cancellation point shall occur for pthread_join, and we use the | |
69ca4b54 | 128 | same rationale for posix_timedjoin_np. Both clockwait_tid and the futex |
eb76e5b4 | 129 | call use the cancellable variant. */ |
4735850f AZ |
130 | if (block) |
131 | { | |
132 | /* During the wait we change to asynchronous cancellation. If we | |
133 | are cancelled the thread we are waiting for must be marked as | |
134 | un-wait-ed for again. */ | |
135 | pthread_cleanup_push (cleanup, &pd->joinid); | |
136 | ||
eb76e5b4 | 137 | if (abstime != NULL) |
69ca4b54 | 138 | result = clockwait_tid (&pd->tid, clockid, abstime); |
eb76e5b4 AZ |
139 | else |
140 | { | |
141 | pid_t tid; | |
142 | /* We need acquire MO here so that we synchronize with the | |
143 | kernel's store to 0 when the clone terminates. (see above) */ | |
144 | while ((tid = atomic_load_acquire (&pd->tid)) != 0) | |
145 | lll_futex_wait_cancel (&pd->tid, tid, LLL_SHARED); | |
146 | } | |
4735850f AZ |
147 | |
148 | pthread_cleanup_pop (0); | |
149 | } | |
150 | ||
bc10e22c | 151 | void *pd_result = pd->result; |
4735850f AZ |
152 | if (__glibc_likely (result == 0)) |
153 | { | |
154 | /* We mark the thread as terminated and as joined. */ | |
155 | pd->tid = -1; | |
156 | ||
157 | /* Store the return value if the caller is interested. */ | |
158 | if (thread_return != NULL) | |
bc10e22c | 159 | *thread_return = pd_result; |
4735850f AZ |
160 | |
161 | /* Free the TCB. */ | |
162 | __free_tcb (pd); | |
163 | } | |
164 | else | |
165 | pd->joinid = NULL; | |
166 | ||
bc10e22c | 167 | LIBC_PROBE (pthread_join_ret, 3, threadid, result, pd_result); |
4735850f AZ |
168 | |
169 | return result; | |
170 | } |