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1 | #ifndef _LTTNG_UST_FUTEX_H |
2 | #define _LTTNG_UST_FUTEX_H | |
3 | ||
4 | /* | |
5 | * liblttng-ust/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 <errno.h> | |
27 | #include <stdint.h> | |
28 | #include <time.h> | |
29 | #include <sys/syscall.h> | |
30 | ||
31 | #ifdef __cplusplus | |
32 | extern "C" { | |
33 | #endif | |
34 | ||
35 | #define FUTEX_WAIT 0 | |
36 | #define FUTEX_WAKE 1 | |
37 | ||
38 | /* | |
39 | * sys_futex compatibility header. | |
40 | * Use *only* *either of* futex_noasync OR futex_async on a given address. | |
41 | * | |
42 | * futex_noasync cannot be executed in signal handlers, but ensures that | |
43 | * it will be put in a wait queue even in compatibility mode. | |
44 | * | |
45 | * futex_async is signal-handler safe for the wakeup. It uses polling | |
46 | * on the wait-side in compatibility mode. | |
47 | * | |
48 | * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted | |
49 | * (returns EINTR). | |
50 | */ | |
51 | ||
52 | extern int lttng_ust_compat_futex_noasync(int32_t *uaddr, int op, int32_t val, | |
53 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3); | |
54 | extern int lttng_ust_compat_futex_async(int32_t *uaddr, int op, int32_t val, | |
55 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3); | |
56 | ||
57 | #if (defined(__linux__) && defined(__NR_futex)) | |
58 | ||
59 | #include <unistd.h> | |
60 | #include <errno.h> | |
61 | #include <urcu/compiler.h> | |
62 | #include <urcu/arch.h> | |
63 | ||
64 | static inline int lttng_ust_futex(int32_t *uaddr, int op, int32_t val, | |
65 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
66 | { | |
67 | return syscall(__NR_futex, uaddr, op, val, timeout, | |
68 | uaddr2, val3); | |
69 | } | |
70 | ||
71 | static inline int lttng_ust_futex_noasync(int32_t *uaddr, int op, int32_t val, | |
72 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
73 | { | |
74 | int ret; | |
75 | ||
76 | ret = lttng_ust_futex(uaddr, op, val, timeout, uaddr2, val3); | |
77 | if (caa_unlikely(ret < 0 && errno == ENOSYS)) { | |
78 | /* | |
79 | * The fallback on ENOSYS is the async-safe version of | |
80 | * the compat futex implementation, because the | |
81 | * async-safe compat implementation allows being used | |
82 | * concurrently with calls to futex(). Indeed, sys_futex | |
83 | * FUTEX_WAIT, on some architectures (mips and parisc), | |
84 | * within a given process, spuriously return ENOSYS due | |
85 | * to signal restart bugs on some kernel versions. | |
86 | */ | |
87 | return lttng_ust_compat_futex_async(uaddr, op, val, timeout, | |
88 | uaddr2, val3); | |
89 | } | |
90 | return ret; | |
91 | ||
92 | } | |
93 | ||
94 | static inline int lttng_ust_futex_async(int32_t *uaddr, int op, int32_t val, | |
95 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
96 | { | |
97 | int ret; | |
98 | ||
99 | ret = lttng_ust_futex(uaddr, op, val, timeout, uaddr2, val3); | |
100 | if (caa_unlikely(ret < 0 && errno == ENOSYS)) { | |
101 | return lttng_ust_compat_futex_async(uaddr, op, val, timeout, | |
102 | uaddr2, val3); | |
103 | } | |
104 | return ret; | |
105 | } | |
106 | ||
107 | #elif defined(__FreeBSD__) | |
108 | ||
109 | #include <sys/types.h> | |
110 | #include <sys/umtx.h> | |
111 | ||
112 | static inline int lttng_ust_futex_async(int32_t *uaddr, int op, int32_t val, | |
113 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
114 | { | |
115 | int umtx_op; | |
116 | void *umtx_uaddr = NULL, *umtx_uaddr2 = NULL; | |
117 | struct _umtx_time umtx_timeout = { | |
118 | ._flags = UMTX_ABSTIME, | |
119 | ._clockid = CLOCK_MONOTONIC, | |
120 | }; | |
121 | ||
122 | switch (op) { | |
123 | case FUTEX_WAIT: | |
124 | /* On FreeBSD, a "u_int" is a 32-bit integer. */ | |
125 | umtx_op = UMTX_OP_WAIT_UINT; | |
126 | if (timeout != NULL) { | |
127 | umtx_timeout._timeout = *timeout; | |
128 | umtx_uaddr = (void *) sizeof(umtx_timeout); | |
129 | umtx_uaddr2 = (void *) &umtx_timeout; | |
130 | } | |
131 | break; | |
132 | case FUTEX_WAKE: | |
133 | umtx_op = UMTX_OP_WAKE; | |
134 | break; | |
135 | default: | |
136 | errno = EINVAL; | |
137 | return -1; | |
138 | } | |
139 | ||
140 | return _umtx_op(uaddr, umtx_op, (uint32_t) val, umtx_uaddr, | |
141 | umtx_uaddr2); | |
142 | } | |
143 | ||
144 | static inline int lttng_ust_futex_noasync(int32_t *uaddr, int op, int32_t val, | |
145 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
146 | { | |
147 | return futex_async(uaddr, op, val, timeout, uaddr2, val3); | |
148 | } | |
149 | ||
150 | #elif defined(__CYGWIN__) | |
151 | ||
152 | /* | |
153 | * The futex_noasync compat code uses a weak symbol to share state across | |
154 | * different shared object which is not possible on Windows with the | |
155 | * Portable Executable format. Use the async compat code for both cases. | |
156 | */ | |
157 | static inline int lttng_ust_futex_noasync(int32_t *uaddr, int op, int32_t val, | |
158 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
159 | { | |
160 | return lttng_ust_compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); | |
161 | } | |
162 | ||
163 | static inline int lttng_ust_futex_async(int32_t *uaddr, int op, int32_t val, | |
164 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
165 | { | |
166 | return lttng_ust_compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); | |
167 | } | |
168 | ||
169 | #else | |
170 | ||
171 | static inline int lttng_ust_futex_noasync(int32_t *uaddr, int op, int32_t val, | |
172 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
173 | { | |
174 | return lttng_ust_compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3); | |
175 | } | |
176 | ||
177 | static inline int lttng_ust_futex_async(int32_t *uaddr, int op, int32_t val, | |
178 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) | |
179 | { | |
180 | return lttng_ust_compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); | |
181 | } | |
182 | ||
183 | #endif | |
184 | ||
185 | #ifdef __cplusplus | |
186 | } | |
187 | #endif | |
188 | ||
189 | #endif /* _LTTNG_UST_FUTEX_H */ |