3f1d1ef3410a91d4ae432080debcba4c6a17e387
[urcu.git] / compat_futex.c
1 /*
2 * compat_futex.c
3 *
4 * Userspace RCU library - sys_futex compatibility code
5 *
6 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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 #include <stdint.h>
30
31 #include <urcu/arch.h>
32 #include <urcu/futex.h>
33
34 static pthread_mutex_t compat_futex_lock = PTHREAD_MUTEX_INITIALIZER;
35 static pthread_cond_t compat_futex_cond = PTHREAD_COND_INITIALIZER;
36
37 /*
38 * _NOT SIGNAL-SAFE_. pthread_cond is not signal-safe anyway. Though.
39 * For now, timeout, uaddr2 and val3 are unused.
40 * Waiter will relinquish the CPU until woken up.
41 */
42
43 int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
44 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
45 {
46 int ret, i, gret = 0;
47
48 /*
49 * Check if NULL. Don't let users expect that they are taken into
50 * account.
51 */
52 assert(!timeout);
53 assert(!uaddr2);
54 assert(!val3);
55
56 /*
57 * memory barriers to serialize with the previous uaddr modification.
58 */
59 cmm_smp_mb();
60
61 ret = pthread_mutex_lock(&compat_futex_lock);
62 assert(!ret);
63 switch (op) {
64 case FUTEX_WAIT:
65 if (*uaddr != val)
66 goto end;
67 pthread_cond_wait(&compat_futex_cond, &compat_futex_lock);
68 break;
69 case FUTEX_WAKE:
70 for (i = 0; i < val; i++)
71 pthread_cond_signal(&compat_futex_cond);
72 break;
73 default:
74 gret = -EINVAL;
75 }
76 end:
77 ret = pthread_mutex_unlock(&compat_futex_lock);
78 assert(!ret);
79 return gret;
80 }
81
82 /*
83 * _ASYNC SIGNAL-SAFE_.
84 * For now, timeout, uaddr2 and val3 are unused.
85 * Waiter will busy-loop trying to read the condition.
86 */
87
88 int compat_futex_async(int32_t *uaddr, int op, int32_t val,
89 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
90 {
91 int ret, i;
92
93 /*
94 * Check if NULL. Don't let users expect that they are taken into
95 * account.
96 */
97 assert(!timeout);
98 assert(!uaddr2);
99 assert(!val3);
100
101 /*
102 * Ensure previous memory operations on uaddr have completed.
103 */
104 cmm_smp_mb();
105
106 switch (op) {
107 case FUTEX_WAIT:
108 while (*uaddr == val)
109 poll(NULL, 0, 10);
110 break;
111 case FUTEX_WAKE:
112 break;
113 default:
114 return -EINVAL;
115 }
116 }
This page took 0.031548 seconds and 4 git commands to generate.