]>
Commit | Line | Data |
---|---|---|
4d17e683 | 1 | /* Copyright (C) 2003-2012 Free Software Foundation, Inc. |
cd2fbe58 UD |
2 | This file is part of the GNU C Library. |
3 | Contributed by Jakub Jelinek <jakub@redhat.com>, 2003. | |
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/>. */ | |
cd2fbe58 UD |
18 | |
19 | #include "pthreadP.h" | |
20 | #include <lowlevellock.h> | |
21 | ||
22 | ||
23 | unsigned long int __fork_generation attribute_hidden; | |
24 | ||
25 | ||
26 | static void | |
27 | clear_once_control (void *arg) | |
28 | { | |
29 | pthread_once_t *once_control = (pthread_once_t *) arg; | |
30 | ||
31 | *once_control = 0; | |
085a4412 | 32 | lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); |
cd2fbe58 UD |
33 | } |
34 | ||
35 | ||
36 | int | |
37 | __pthread_once (once_control, init_routine) | |
38 | pthread_once_t *once_control; | |
39 | void (*init_routine) (void); | |
40 | { | |
41 | while (1) | |
42 | { | |
43 | int oldval, val, newval; | |
44 | ||
45 | val = *once_control; | |
46 | do | |
47 | { | |
48 | /* Check if the initialized has already been done. */ | |
49 | if ((val & 2) != 0) | |
50 | return 0; | |
51 | ||
52 | oldval = val; | |
53 | newval = (oldval & 3) | __fork_generation | 1; | |
54 | val = atomic_compare_and_exchange_val_acq (once_control, newval, | |
55 | oldval); | |
56 | } | |
57 | while (__builtin_expect (val != oldval, 0)); | |
58 | ||
59 | /* Check if another thread already runs the initializer. */ | |
60 | if ((oldval & 1) != 0) | |
61 | { | |
62 | /* Check whether the initializer execution was interrupted | |
63 | by a fork. */ | |
64 | if (((oldval ^ newval) & -4) == 0) | |
65 | { | |
66 | /* Same generation, some other thread was faster. Wait. */ | |
085a4412 | 67 | lll_futex_wait (once_control, newval, LLL_PRIVATE); |
cd2fbe58 UD |
68 | continue; |
69 | } | |
70 | } | |
71 | ||
72 | /* This thread is the first here. Do the initialization. | |
73 | Register a cleanup handler so that in case the thread gets | |
74 | interrupted the initialization can be restarted. */ | |
75 | pthread_cleanup_push (clear_once_control, once_control); | |
76 | ||
77 | init_routine (); | |
78 | ||
79 | pthread_cleanup_pop (0); | |
80 | ||
81 | ||
82 | /* Add one to *once_control. */ | |
67254a97 | 83 | atomic_increment (once_control); |
cd2fbe58 UD |
84 | |
85 | /* Wake up all other threads. */ | |
085a4412 | 86 | lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); |
cd2fbe58 UD |
87 | break; |
88 | } | |
89 | ||
90 | return 0; | |
91 | } | |
92 | weak_alias (__pthread_once, pthread_once) | |
4d17e683 | 93 | hidden_def (__pthread_once) |