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comparison libgomp/config/linux/bar.c @ 0:a06113de4d67

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author kent <kent@cr.ie.u-ryukyu.ac.jp>
date Fri, 17 Jul 2009 14:47:48 +0900
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children 04ced10e8804
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-1:000000000000 0:a06113de4d67
1 /* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc.
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
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.
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
13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
14 more details.
15
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.
19
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/>. */
24
25 /* This is a Linux specific implementation of a barrier synchronization
26 mechanism for libgomp. This type is private to the library. This
27 implementation uses atomic instructions and the futex syscall. */
28
29 #include <limits.h>
30 #include "wait.h"
31
32
33 void
34 gomp_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
35 {
36 if (__builtin_expect ((state & 1) != 0, 0))
37 {
38 /* Next time we'll be awaiting TOTAL threads again. */
39 bar->awaited = bar->total;
40 atomic_write_barrier ();
41 bar->generation += 4;
42 futex_wake ((int *) &bar->generation, INT_MAX);
43 }
44 else
45 {
46 unsigned int generation = state;
47
48 do
49 do_wait ((int *) &bar->generation, generation);
50 while (bar->generation == generation);
51 }
52 }
53
54 void
55 gomp_barrier_wait (gomp_barrier_t *bar)
56 {
57 gomp_barrier_wait_end (bar, gomp_barrier_wait_start (bar));
58 }
59
60 /* Like gomp_barrier_wait, except that if the encountering thread
61 is not the last one to hit the barrier, it returns immediately.
62 The intended usage is that a thread which intends to gomp_barrier_destroy
63 this barrier calls gomp_barrier_wait, while all other threads
64 call gomp_barrier_wait_last. When gomp_barrier_wait returns,
65 the barrier can be safely destroyed. */
66
67 void
68 gomp_barrier_wait_last (gomp_barrier_t *bar)
69 {
70 gomp_barrier_state_t state = gomp_barrier_wait_start (bar);
71 if (state & 1)
72 gomp_barrier_wait_end (bar, state);
73 }
74
75 void
76 gomp_team_barrier_wake (gomp_barrier_t *bar, int count)
77 {
78 futex_wake ((int *) &bar->generation, count == 0 ? INT_MAX : count);
79 }
80
81 void
82 gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
83 {
84 unsigned int generation;
85
86 if (__builtin_expect ((state & 1) != 0, 0))
87 {
88 /* Next time we'll be awaiting TOTAL threads again. */
89 struct gomp_thread *thr = gomp_thread ();
90 struct gomp_team *team = thr->ts.team;
91 bar->awaited = bar->total;
92 atomic_write_barrier ();
93 if (__builtin_expect (team->task_count, 0))
94 {
95 gomp_barrier_handle_tasks (state);
96 state &= ~1;
97 }
98 else
99 {
100 bar->generation = state + 3;
101 futex_wake ((int *) &bar->generation, INT_MAX);
102 return;
103 }
104 }
105
106 generation = state;
107 do
108 {
109 do_wait ((int *) &bar->generation, generation);
110 if (__builtin_expect (bar->generation & 1, 0))
111 gomp_barrier_handle_tasks (state);
112 if ((bar->generation & 2))
113 generation |= 2;
114 }
115 while (bar->generation != state + 4);
116 }
117
118 void
119 gomp_team_barrier_wait (gomp_barrier_t *bar)
120 {
121 gomp_team_barrier_wait_end (bar, gomp_barrier_wait_start (bar));
122 }