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comparison libgomp/config/linux/sem.h @ 111:04ced10e8804

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gcc 7
author kono
date Fri, 27 Oct 2017 22:46:09 +0900
parents a06113de4d67
children 84e7813d76e9
comparison
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68:561a7518be6b 111:04ced10e8804
1 /* Copyright (C) 2005, 2009 Free Software Foundation, Inc. 1 /* Copyright (C) 2005-2017 Free Software Foundation, Inc.
2 Contributed by Richard Henderson <rth@redhat.com>. 2 Contributed by Richard Henderson <rth@redhat.com>.
3 3
4 This file is part of the GNU OpenMP Library (libgomp). 4 This file is part of the GNU Offloading and Multi Processing Library
5 (libgomp).
5 6
6 Libgomp is free software; you can redistribute it and/or modify it 7 Libgomp is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by 8 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 the Free Software Foundation; either version 3, or (at your option)
9 any later version. 10 any later version.
22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 <http://www.gnu.org/licenses/>. */ 24 <http://www.gnu.org/licenses/>. */
24 25
25 /* This is a Linux specific implementation of a semaphore synchronization 26 /* This is a Linux specific implementation of a semaphore synchronization
26 mechanism for libgomp. This type is private to the library. This 27 mechanism for libgomp. This type is private to the library. This
27 implementation uses atomic instructions and the futex syscall. */ 28 counting semaphore implementation uses atomic instructions and the
29 futex syscall, and a single 32-bit int to store semaphore state.
30 The low 31 bits are the count, the top bit is a flag set when some
31 threads may be waiting. */
28 32
29 #ifndef GOMP_SEM_H 33 #ifndef GOMP_SEM_H
30 #define GOMP_SEM_H 1 34 #define GOMP_SEM_H 1
31 35
36 #include <limits.h> /* For INT_MIN */
37
32 typedef int gomp_sem_t; 38 typedef int gomp_sem_t;
39 #define SEM_WAIT INT_MIN
40 #define SEM_INC 1
33 41
34 static inline void gomp_sem_init (gomp_sem_t *sem, int value) 42 extern void gomp_sem_wait_slow (gomp_sem_t *, int);
43 extern void gomp_sem_post_slow (gomp_sem_t *);
44
45 static inline void
46 gomp_sem_init (gomp_sem_t *sem, int value)
35 { 47 {
36 *sem = value; 48 *sem = value * SEM_INC;
37 } 49 }
38 50
39 extern void gomp_sem_wait_slow (gomp_sem_t *); 51 static inline void
40 static inline void gomp_sem_wait (gomp_sem_t *sem) 52 gomp_sem_destroy (gomp_sem_t *sem)
41 {
42 if (!__sync_bool_compare_and_swap (sem, 1, 0))
43 gomp_sem_wait_slow (sem);
44 }
45
46 extern void gomp_sem_post_slow (gomp_sem_t *);
47 static inline void gomp_sem_post (gomp_sem_t *sem)
48 {
49 if (!__sync_bool_compare_and_swap (sem, 0, 1))
50 gomp_sem_post_slow (sem);
51 }
52
53 static inline void gomp_sem_destroy (gomp_sem_t *sem)
54 { 53 {
55 } 54 }
56 55
56 static inline void
57 gomp_sem_wait (gomp_sem_t *sem)
58 {
59 int count = *sem;
60
61 while ((count & ~SEM_WAIT) != 0)
62 if (__atomic_compare_exchange_n (sem, &count, count - SEM_INC, true,
63 MEMMODEL_ACQUIRE, MEMMODEL_RELAXED))
64 return;
65 gomp_sem_wait_slow (sem, count);
66 }
67
68 static inline void
69 gomp_sem_post (gomp_sem_t *sem)
70 {
71 int count = *sem;
72
73 /* Clear SEM_WAIT here so that if there are no more waiting threads
74 we transition back to the uncontended state that does not make
75 futex syscalls. If there are waiting threads then when one is
76 awoken it will set SEM_WAIT again, so other waiting threads are
77 woken on a future gomp_sem_post. Furthermore, the awoken thread
78 will wake other threads in case gomp_sem_post was called again
79 before it had time to set SEM_WAIT. */
80 while (!__atomic_compare_exchange_n (sem, &count,
81 (count + SEM_INC) & ~SEM_WAIT, true,
82 MEMMODEL_RELEASE, MEMMODEL_RELAXED))
83 continue;
84
85 if (__builtin_expect (count & SEM_WAIT, 0))
86 gomp_sem_post_slow (sem);
87 }
57 #endif /* GOMP_SEM_H */ 88 #endif /* GOMP_SEM_H */