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748086b7 | 1 | /* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc. |
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2 | Contributed by Richard Henderson <rth@redhat.com>. |
3 | ||
4 | This file is part of the GNU OpenMP Library (libgomp). | |
5 | ||
6 | Libgomp is free software; you can redistribute it and/or modify it | |
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7 | under the terms of the GNU General Public License as published by |
8 | the Free Software Foundation; either version 3, or (at your option) | |
9 | any later version. | |
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10 | |
11 | Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY | |
12 | WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS | |
748086b7 | 13 | FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
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14 | more details. |
15 | ||
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16 | Under Section 7 of GPL version 3, you are granted additional |
17 | permissions described in the GCC Runtime Library Exception, version | |
18 | 3.1, as published by the Free Software Foundation. | |
953ff289 | 19 | |
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20 | You should have received a copy of the GNU General Public License and |
21 | a copy of the GCC Runtime Library Exception along with this program; | |
22 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
23 | <http://www.gnu.org/licenses/>. */ | |
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24 | |
25 | /* This is a Linux specific implementation of a semaphore synchronization | |
26 | mechanism for libgomp. This type is private to the library. This | |
27 | implementation uses atomic instructions and the futex syscall. */ | |
28 | ||
a68ab351 | 29 | #include "wait.h" |
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30 | |
31 | ||
32 | void | |
33 | gomp_sem_wait_slow (gomp_sem_t *sem) | |
34 | { | |
35 | while (1) | |
36 | { | |
37 | int val = __sync_val_compare_and_swap (sem, 0, -1); | |
38 | if (val > 0) | |
39 | { | |
40 | if (__sync_bool_compare_and_swap (sem, val, val - 1)) | |
41 | return; | |
42 | } | |
a68ab351 | 43 | do_wait (sem, -1); |
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44 | } |
45 | } | |
46 | ||
47 | void | |
48 | gomp_sem_post_slow (gomp_sem_t *sem) | |
49 | { | |
50 | int old, tmp = *sem, wake; | |
51 | ||
52 | do | |
53 | { | |
54 | old = tmp; | |
55 | wake = old > 0 ? old + 1 : 1; | |
56 | tmp = __sync_val_compare_and_swap (sem, old, wake); | |
57 | } | |
58 | while (old != tmp); | |
59 | ||
60 | futex_wake (sem, wake); | |
61 | } |