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7adcbafe | 1 | /* Copyright (C) 2008-2022 Free Software Foundation, Inc. |
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2 | Contributed by Jakub Jelinek <jakub@redhat.com>. |
3 | ||
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4 | This file is part of the GNU Offloading and Multi Processing Library |
5 | (libgomp). | |
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6 | |
7 | Libgomp is free software; you can redistribute it and/or modify it | |
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8 | under the terms of the GNU General Public License as published by |
9 | the Free Software Foundation; either version 3, or (at your option) | |
10 | any later version. | |
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11 | |
12 | Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 | WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS | |
748086b7 | 14 | FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
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15 | more details. |
16 | ||
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17 | Under Section 7 of GPL version 3, you are granted additional |
18 | permissions described in the GCC Runtime Library Exception, version | |
19 | 3.1, as published by the Free Software Foundation. | |
a68ab351 | 20 | |
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21 | You should have received a copy of the GNU General Public License and |
22 | a copy of the GCC Runtime Library Exception along with this program; | |
23 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
24 | <http://www.gnu.org/licenses/>. */ | |
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25 | |
26 | /* This is a Linux specific implementation of a mutex synchronization | |
27 | mechanism for libgomp. This type is private to the library. This | |
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28 | implementation uses atomic instructions and the futex syscall. |
29 | ||
30 | A ptrlock has four states: | |
31 | 0/NULL Initial | |
32 | 1 Owned by me, I get to write a pointer to ptrlock. | |
33 | 2 Some thread is waiting on the ptrlock. | |
34 | >2 Ptrlock contains a valid pointer. | |
35 | It is not valid to gain the ptrlock and then write a NULL to it. */ | |
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36 | |
37 | #ifndef GOMP_PTRLOCK_H | |
38 | #define GOMP_PTRLOCK_H 1 | |
39 | ||
40 | typedef void *gomp_ptrlock_t; | |
41 | ||
42 | static inline void gomp_ptrlock_init (gomp_ptrlock_t *ptrlock, void *ptr) | |
43 | { | |
44 | *ptrlock = ptr; | |
45 | } | |
46 | ||
47 | extern void *gomp_ptrlock_get_slow (gomp_ptrlock_t *ptrlock); | |
48 | static inline void *gomp_ptrlock_get (gomp_ptrlock_t *ptrlock) | |
49 | { | |
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50 | uintptr_t oldval; |
51 | ||
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52 | uintptr_t v = (uintptr_t) __atomic_load_n (ptrlock, MEMMODEL_ACQUIRE); |
53 | if (v > 2) | |
54 | return (void *) v; | |
a68ab351 | 55 | |
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56 | oldval = 0; |
57 | if (__atomic_compare_exchange_n (ptrlock, &oldval, 1, false, | |
58 | MEMMODEL_ACQUIRE, MEMMODEL_ACQUIRE)) | |
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59 | return NULL; |
60 | ||
61 | return gomp_ptrlock_get_slow (ptrlock); | |
62 | } | |
63 | ||
45608a43 | 64 | extern void gomp_ptrlock_set_slow (gomp_ptrlock_t *ptrlock); |
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65 | static inline void gomp_ptrlock_set (gomp_ptrlock_t *ptrlock, void *ptr) |
66 | { | |
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67 | void *wait = __atomic_exchange_n (ptrlock, ptr, MEMMODEL_RELEASE); |
68 | if ((uintptr_t) wait != 1) | |
69 | gomp_ptrlock_set_slow (ptrlock); | |
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70 | } |
71 | ||
72 | static inline void gomp_ptrlock_destroy (gomp_ptrlock_t *ptrlock) | |
73 | { | |
74 | } | |
75 | ||
76 | #endif /* GOMP_PTRLOCK_H */ |