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04277e02 | 1 | /* Copyright (C) 2002-2019 Free Software Foundation, Inc. |
76a50749 UD |
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 | |
59ba27a6 PE |
16 | License along with the GNU C Library; if not, see |
17 | <http://www.gnu.org/licenses/>. */ | |
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18 | |
19 | #include <errno.h> | |
20 | #include "pthreadP.h" | |
b02840ba TR |
21 | #include <atomic.h> |
22 | #include <futex-internal.h> | |
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23 | |
24 | ||
25 | int | |
9d46370c | 26 | pthread_barrier_destroy (pthread_barrier_t *barrier) |
76a50749 | 27 | { |
b02840ba TR |
28 | struct pthread_barrier *bar = (struct pthread_barrier *) barrier; |
29 | ||
30 | /* Destroying a barrier is only allowed if no thread is blocked on it. | |
31 | Thus, there is no unfinished round, and all modifications to IN will | |
32 | have happened before us (either because the calling thread took part | |
33 | in the most recent round and thus synchronized-with all other threads | |
34 | entering, or the program ensured this through other synchronization). | |
35 | We must wait until all threads that entered so far have confirmed that | |
36 | they have exited as well. To get the notification, pretend that we have | |
37 | reached the reset threshold. */ | |
38 | unsigned int count = bar->count; | |
39 | unsigned int max_in_before_reset = BARRIER_IN_THRESHOLD | |
40 | - BARRIER_IN_THRESHOLD % count; | |
41 | /* Relaxed MO sufficient because the program must have ensured that all | |
42 | modifications happen-before this load (see above). */ | |
43 | unsigned int in = atomic_load_relaxed (&bar->in); | |
44 | /* Trigger reset. The required acquire MO is below. */ | |
45 | if (atomic_fetch_add_relaxed (&bar->out, max_in_before_reset - in) < in) | |
46 | { | |
47 | /* Not all threads confirmed yet that they have exited, so another | |
48 | thread will perform a reset. Wait until that has happened. */ | |
49 | while (in != 0) | |
50 | { | |
51 | futex_wait_simple (&bar->in, in, bar->shared); | |
52 | in = atomic_load_relaxed (&bar->in); | |
53 | } | |
54 | } | |
55 | /* We must ensure that memory reuse happens after all prior use of the | |
56 | barrier (specifically, synchronize-with the reset of the barrier or the | |
57 | confirmation of threads leaving the barrier). */ | |
58 | atomic_thread_fence_acquire (); | |
59 | ||
60 | return 0; | |
76a50749 | 61 | } |