Fix: uatomic arm32: add missing release barrier before uatomic_xchg
[urcu.git] / include / urcu / futex.h
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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 *
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9 * Copyright 2011-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 *
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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>
6d841bc2 27#include <stdint.h>
49617de1 28
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29#ifdef __cplusplus
30extern "C" {
67ecffc0 31#endif
36bc70a8 32
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33#define FUTEX_WAIT 0
34#define FUTEX_WAKE 1
35
36/*
37 * sys_futex compatibility header.
38 * Use *only* *either of* futex_noasync OR futex_async on a given address.
39 *
40 * futex_noasync cannot be executed in signal handlers, but ensures that
41 * it will be put in a wait queue even in compatibility mode.
42 *
43 * futex_async is signal-handler safe for the wakeup. It uses polling
44 * on the wait-side in compatibility mode.
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45 *
46 * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted
47 * (returns EINTR).
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48 */
49
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50extern int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
51 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
52extern int compat_futex_async(int32_t *uaddr, int op, int32_t val,
53 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
54
02be5561 55#ifdef CONFIG_RCU_HAVE_FUTEX
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56
57#include <unistd.h>
58#include <errno.h>
59#include <urcu/compiler.h>
999991c6 60#include <urcu/arch.h>
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61
62static inline int futex(int32_t *uaddr, int op, int32_t val,
63 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
64{
65 return syscall(__NR_futex, uaddr, op, val, timeout,
66 uaddr2, val3);
67}
68
69static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
70 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
71{
72 int ret;
73
74 ret = futex(uaddr, op, val, timeout, uaddr2, val3);
75 if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
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76 /*
77 * The fallback on ENOSYS is the async-safe version of
78 * the compat futex implementation, because the
79 * async-safe compat implementation allows being used
80 * concurrently with calls to futex(). Indeed, sys_futex
81 * FUTEX_WAIT, on some architectures (mips and parisc),
82 * within a given process, spuriously return ENOSYS due
83 * to signal restart bugs on some kernel versions.
84 */
85 return compat_futex_async(uaddr, op, val, timeout,
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86 uaddr2, val3);
87 }
88 return ret;
89
90}
91
92static inline int futex_async(int32_t *uaddr, int op, int32_t val,
93 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
94{
95 int ret;
96
97 ret = futex(uaddr, op, val, timeout, uaddr2, val3);
98 if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
99 return compat_futex_async(uaddr, op, val, timeout,
100 uaddr2, val3);
101 }
102 return ret;
103}
104
49617de1 105#else
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106
107static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
108 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
109{
110 return compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3);
111}
112
113static inline int futex_async(int32_t *uaddr, int op, int32_t val,
114 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
115{
116 return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
117}
118
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119#endif
120
67ecffc0 121#ifdef __cplusplus
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122}
123#endif
124
49617de1 125#endif /* _URCU_FUTEX_H */
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