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49617de1 MD |
1 | /* |
2 | * compat_futex.c | |
3 | * | |
4 | * Userspace RCU library - sys_futex compatibility code | |
5 | * | |
6 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> | |
7 | * | |
8 | * This library is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU Lesser General Public | |
10 | * License as published by the Free Software Foundation; either | |
11 | * version 2.1 of the License, or (at your option) any later version. | |
12 | * | |
13 | * This library is distributed in the hope that it will be useful, | |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | * Lesser General Public License for more details. | |
17 | * | |
18 | * You should have received a copy of the GNU Lesser General Public | |
19 | * License along with this library; if not, write to the Free Software | |
20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
21 | */ | |
22 | ||
23 | #include <stdio.h> | |
24 | #include <pthread.h> | |
25 | #include <signal.h> | |
26 | #include <assert.h> | |
27 | #include <errno.h> | |
28 | #include <poll.h> | |
29 | ||
30 | #include <urcu/arch.h> | |
31 | #include <urcu/urcu-futex.h> | |
32 | ||
33 | static pthread_mutex_t compat_futex_lock = PTHREAD_MUTEX_INITIALIZER; | |
34 | static pthread_cond_t compat_futex_cond = PTHREAD_COND_INITIALIZER; | |
35 | ||
36 | /* | |
37 | * _NOT SIGNAL-SAFE_. pthread_cond is not signal-safe anyway. Though. | |
38 | * For now, timeout, uaddr2 and val3 are unused. | |
39 | * Waiter will relinquish the CPU until woken up. | |
40 | */ | |
41 | ||
42 | int compat_futex_noasync(int *uaddr, int op, int val, | |
43 | const struct timespec *timeout, int *uaddr2, int val3) | |
44 | { | |
45 | int ret, i, gret = 0; | |
46 | ||
47 | /* | |
48 | * Check if NULL. Don't let users expect that they are taken into | |
49 | * account. | |
50 | */ | |
51 | assert(!timeout); | |
52 | assert(!uaddr2); | |
53 | assert(!val3); | |
54 | ||
55 | /* | |
56 | * memory barriers to serialize with the previous uaddr modification. | |
57 | */ | |
58 | smp_mb(); | |
59 | ||
60 | ret = pthread_mutex_lock(&compat_futex_lock); | |
61 | assert(!ret); | |
62 | switch (op) { | |
63 | case FUTEX_WAIT: | |
64 | if (*uaddr != val) | |
65 | goto end; | |
66 | pthread_cond_wait(&compat_futex_cond, &compat_futex_lock); | |
67 | break; | |
68 | case FUTEX_WAKE: | |
69 | for (i = 0; i < val; i++) | |
70 | pthread_cond_signal(&compat_futex_cond); | |
71 | break; | |
72 | default: | |
73 | gret = -EINVAL; | |
74 | } | |
75 | end: | |
76 | ret = pthread_mutex_unlock(&compat_futex_lock); | |
77 | assert(!ret); | |
78 | return gret; | |
79 | } | |
80 | ||
81 | /* | |
82 | * _ASYNC SIGNAL-SAFE_. | |
83 | * For now, timeout, uaddr2 and val3 are unused. | |
84 | * Waiter will busy-loop trying to read the condition. | |
85 | */ | |
86 | ||
87 | int compat_futex_async(int *uaddr, int op, int val, | |
88 | const struct timespec *timeout, int *uaddr2, int val3) | |
89 | { | |
90 | int ret, i; | |
91 | ||
92 | /* | |
93 | * Check if NULL. Don't let users expect that they are taken into | |
94 | * account. | |
95 | */ | |
96 | assert(!timeout); | |
97 | assert(!uaddr2); | |
98 | assert(!val3); | |
99 | ||
100 | /* | |
101 | * Ensure previous memory operations on uaddr have completed. | |
102 | */ | |
103 | smp_mb(); | |
104 | ||
105 | switch (op) { | |
106 | case FUTEX_WAIT: | |
107 | while (*uaddr == val) | |
108 | poll(NULL, 0, 10); | |
109 | break; | |
110 | case FUTEX_WAKE: | |
111 | break; | |
112 | default: | |
113 | return -EINVAL; | |
114 | } | |
115 | } |