753cf16d9e28d6c79639e915fd633175121c0315
[urcu.git] / include / urcu / futex.h
1 #ifndef _URCU_FUTEX_H
2 #define _URCU_FUTEX_H
3
4 /*
5 * urcu-futex.h
6 *
7 * Userspace RCU - sys_futex/compat_futex header.
8 *
9 * Copyright 2011-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 *
11 * This library is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU Lesser General Public
13 * License as published by the Free Software Foundation; either
14 * version 2.1 of the License, or (at your option) any later version.
15 *
16 * This library is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 * Lesser General Public License for more details.
20 *
21 * You should have received a copy of the GNU Lesser General Public
22 * License along with this library; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 */
25
26 #include <urcu/config.h>
27 #include <urcu/syscall-compat.h>
28
29 #include <errno.h>
30 #include <stdint.h>
31 #include <time.h>
32
33 #ifdef __cplusplus
34 extern "C" {
35 #endif
36
37 #define FUTEX_WAIT 0
38 #define FUTEX_WAKE 1
39
40 /*
41 * sys_futex compatibility header.
42 * Use *only* *either of* futex_noasync OR futex_async on a given address.
43 *
44 * futex_noasync cannot be executed in signal handlers, but ensures that
45 * it will be put in a wait queue even in compatibility mode.
46 *
47 * futex_async is signal-handler safe for the wakeup. It uses polling
48 * on the wait-side in compatibility mode.
49 *
50 * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted
51 * (returns EINTR).
52 */
53
54 extern int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
55 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
56 extern int compat_futex_async(int32_t *uaddr, int op, int32_t val,
57 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
58
59 #if (defined(__linux__) && defined(__NR_futex))
60
61 /* For backwards compat */
62 #define CONFIG_RCU_HAVE_FUTEX 1
63
64 #include <unistd.h>
65 #include <errno.h>
66 #include <urcu/compiler.h>
67 #include <urcu/arch.h>
68
69 static inline int futex(int32_t *uaddr, int op, int32_t val,
70 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
71 {
72 return syscall(__NR_futex, uaddr, op, val, timeout,
73 uaddr2, val3);
74 }
75
76 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
77 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
78 {
79 int ret;
80
81 ret = futex(uaddr, op, val, timeout, uaddr2, val3);
82 if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
83 /*
84 * The fallback on ENOSYS is the async-safe version of
85 * the compat futex implementation, because the
86 * async-safe compat implementation allows being used
87 * concurrently with calls to futex(). Indeed, sys_futex
88 * FUTEX_WAIT, on some architectures (mips and parisc),
89 * within a given process, spuriously return ENOSYS due
90 * to signal restart bugs on some kernel versions.
91 */
92 return compat_futex_async(uaddr, op, val, timeout,
93 uaddr2, val3);
94 }
95 return ret;
96
97 }
98
99 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
100 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
101 {
102 int ret;
103
104 ret = futex(uaddr, op, val, timeout, uaddr2, val3);
105 if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
106 return compat_futex_async(uaddr, op, val, timeout,
107 uaddr2, val3);
108 }
109 return ret;
110 }
111
112 #elif defined(__FreeBSD__)
113
114 #include <sys/types.h>
115 #include <sys/umtx.h>
116
117 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
118 const struct timespec *timeout,
119 int32_t *uaddr2 __attribute__((unused)),
120 int32_t val3 __attribute__((unused)))
121 {
122 int umtx_op;
123 void *umtx_uaddr = NULL, *umtx_uaddr2 = NULL;
124 struct _umtx_time umtx_timeout = {
125 ._flags = UMTX_ABSTIME,
126 ._clockid = CLOCK_MONOTONIC,
127 };
128
129 switch (op) {
130 case FUTEX_WAIT:
131 /* On FreeBSD, a "u_int" is a 32-bit integer. */
132 umtx_op = UMTX_OP_WAIT_UINT;
133 if (timeout != NULL) {
134 umtx_timeout._timeout = *timeout;
135 umtx_uaddr = (void *) sizeof(umtx_timeout);
136 umtx_uaddr2 = (void *) &umtx_timeout;
137 }
138 break;
139 case FUTEX_WAKE:
140 umtx_op = UMTX_OP_WAKE;
141 break;
142 default:
143 errno = EINVAL;
144 return -1;
145 }
146
147 return _umtx_op(uaddr, umtx_op, (uint32_t) val, umtx_uaddr,
148 umtx_uaddr2);
149 }
150
151 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
152 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
153 {
154 return futex_async(uaddr, op, val, timeout, uaddr2, val3);
155 }
156
157 #elif defined(__CYGWIN__)
158
159 /*
160 * The futex_noasync compat code uses a weak symbol to share state across
161 * different shared object which is not possible on Windows with the
162 * Portable Executable format. Use the async compat code for both cases.
163 */
164 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
165 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
166 {
167 return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
168 }
169
170 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
171 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
172 {
173 return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
174 }
175
176 #else
177
178 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
179 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
180 {
181 return compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3);
182 }
183
184 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
185 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
186 {
187 return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
188 }
189
190 #endif
191
192 #ifdef __cplusplus
193 }
194 #endif
195
196 #endif /* _URCU_FUTEX_H */
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