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1 | /* |
2 | * Distributed under the Boost Software License, Version 1.0. | |
3 | * (See accompanying file LICENSE_1_0.txt or copy at | |
4 | * http://www.boost.org/LICENSE_1_0.txt) | |
5 | * | |
6 | * Copyright (c) 2020 Andrey Semashev | |
7 | */ | |
8 | /*! | |
9 | * \file atomic/detail/futex.hpp | |
10 | * | |
11 | * This header defines wrappers around futex syscall. | |
12 | * | |
13 | * http://man7.org/linux/man-pages/man2/futex.2.html | |
14 | * https://man.openbsd.org/futex | |
15 | */ | |
16 | ||
17 | #ifndef BOOST_ATOMIC_DETAIL_FUTEX_HPP_INCLUDED_ | |
18 | #define BOOST_ATOMIC_DETAIL_FUTEX_HPP_INCLUDED_ | |
19 | ||
20 | #include <boost/atomic/detail/config.hpp> | |
21 | ||
22 | #ifdef BOOST_HAS_PRAGMA_ONCE | |
23 | #pragma once | |
24 | #endif | |
25 | ||
26 | #if defined(__linux__) || defined(__OpenBSD__) || defined(__NETBSD__) || defined(__NetBSD__) | |
27 | ||
28 | #include <sys/syscall.h> | |
29 | ||
20effc67 TL |
30 | #if defined(SYS_futex) |
31 | #define BOOST_ATOMIC_DETAIL_SYS_FUTEX SYS_futex | |
1e59de90 TL |
32 | #elif defined(SYS_futex_time64) |
33 | // On some 32-bit targets (e.g. riscv32) SYS_futex is not defined and instead SYS_futex_time64 is implemented, | |
34 | // which is equivalent to SYS_futex but uses 64-bit time_t. | |
35 | #define BOOST_ATOMIC_DETAIL_SYS_FUTEX SYS_futex_time64 | |
20effc67 | 36 | #elif defined(__NR_futex) |
1e59de90 | 37 | // Some Android NDKs (Google NDK and older Crystax.NET NDK versions) don't define SYS_futex. |
20effc67 TL |
38 | #define BOOST_ATOMIC_DETAIL_SYS_FUTEX __NR_futex |
39 | #elif defined(SYS___futex) | |
40 | // NetBSD defines SYS___futex, which has slightly different parameters. Basically, it has decoupled timeout and val2 parameters: | |
41 | // int __futex(int *addr1, int op, int val1, const struct timespec *timeout, int *addr2, int val2, int val3); | |
42 | // https://ftp.netbsd.org/pub/NetBSD/NetBSD-current/src/sys/sys/syscall.h | |
43 | // http://bxr.su/NetBSD/sys/kern/sys_futex.c | |
44 | #define BOOST_ATOMIC_DETAIL_SYS_FUTEX SYS___futex | |
45 | #define BOOST_ATOMIC_DETAIL_NETBSD_FUTEX | |
46 | #endif | |
47 | ||
48 | #if defined(BOOST_ATOMIC_DETAIL_SYS_FUTEX) | |
49 | ||
50 | #include <cstddef> | |
51 | #if defined(__linux__) | |
52 | #include <linux/futex.h> | |
53 | #else | |
54 | #include <sys/futex.h> | |
55 | #endif | |
56 | #include <boost/atomic/detail/intptr.hpp> | |
57 | #include <boost/atomic/detail/header.hpp> | |
58 | ||
59 | #define BOOST_ATOMIC_DETAIL_HAS_FUTEX | |
60 | ||
61 | #if defined(FUTEX_PRIVATE_FLAG) | |
62 | #define BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG FUTEX_PRIVATE_FLAG | |
1e59de90 TL |
63 | #elif defined(__ANDROID__) |
64 | // On Android, futex.h is lacking many definitions, but the actual Linux kernel supports the API in full. | |
65 | #define BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG 128 | |
20effc67 TL |
66 | #else |
67 | #define BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG 0 | |
68 | #endif | |
69 | ||
70 | namespace boost { | |
71 | namespace atomics { | |
72 | namespace detail { | |
73 | ||
74 | //! Invokes an operation on the futex | |
75 | BOOST_FORCEINLINE int futex_invoke(void* addr1, int op, unsigned int val1, const void* timeout = NULL, void* addr2 = NULL, unsigned int val3 = 0) BOOST_NOEXCEPT | |
76 | { | |
77 | #if !defined(BOOST_ATOMIC_DETAIL_NETBSD_FUTEX) | |
78 | return ::syscall(BOOST_ATOMIC_DETAIL_SYS_FUTEX, addr1, op, val1, timeout, addr2, val3); | |
79 | #else | |
80 | // Pass 0 in val2. | |
81 | return ::syscall(BOOST_ATOMIC_DETAIL_SYS_FUTEX, addr1, op, val1, timeout, addr2, 0u, val3); | |
82 | #endif | |
83 | } | |
84 | ||
85 | //! Invokes an operation on the futex | |
86 | BOOST_FORCEINLINE int futex_invoke(void* addr1, int op, unsigned int val1, unsigned int val2, void* addr2 = NULL, unsigned int val3 = 0) BOOST_NOEXCEPT | |
87 | { | |
88 | #if !defined(BOOST_ATOMIC_DETAIL_NETBSD_FUTEX) | |
89 | return ::syscall(BOOST_ATOMIC_DETAIL_SYS_FUTEX, addr1, op, val1, static_cast< atomics::detail::uintptr_t >(val2), addr2, val3); | |
90 | #else | |
91 | // Pass NULL in timeout. | |
92 | return ::syscall(BOOST_ATOMIC_DETAIL_SYS_FUTEX, addr1, op, val1, static_cast< void* >(NULL), addr2, val2, val3); | |
93 | #endif | |
94 | } | |
95 | ||
96 | //! Checks that the value \c pval is \c expected and blocks | |
97 | BOOST_FORCEINLINE int futex_wait(void* pval, unsigned int expected) BOOST_NOEXCEPT | |
98 | { | |
99 | return futex_invoke(pval, FUTEX_WAIT, expected); | |
100 | } | |
101 | ||
102 | //! Checks that the value \c pval is \c expected and blocks | |
103 | BOOST_FORCEINLINE int futex_wait_private(void* pval, unsigned int expected) BOOST_NOEXCEPT | |
104 | { | |
105 | return futex_invoke(pval, FUTEX_WAIT | BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG, expected); | |
106 | } | |
107 | ||
108 | //! Wakes the specified number of threads waiting on the futex | |
109 | BOOST_FORCEINLINE int futex_signal(void* pval, unsigned int count = 1u) BOOST_NOEXCEPT | |
110 | { | |
111 | return futex_invoke(pval, FUTEX_WAKE, count); | |
112 | } | |
113 | ||
114 | //! Wakes the specified number of threads waiting on the futex | |
115 | BOOST_FORCEINLINE int futex_signal_private(void* pval, unsigned int count = 1u) BOOST_NOEXCEPT | |
116 | { | |
117 | return futex_invoke(pval, FUTEX_WAKE | BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG, count); | |
118 | } | |
119 | ||
120 | //! Wakes all threads waiting on the futex | |
121 | BOOST_FORCEINLINE int futex_broadcast(void* pval) BOOST_NOEXCEPT | |
122 | { | |
123 | return futex_signal(pval, (~static_cast< unsigned int >(0u)) >> 1); | |
124 | } | |
125 | ||
126 | //! Wakes all threads waiting on the futex | |
127 | BOOST_FORCEINLINE int futex_broadcast_private(void* pval) BOOST_NOEXCEPT | |
128 | { | |
129 | return futex_signal_private(pval, (~static_cast< unsigned int >(0u)) >> 1); | |
130 | } | |
131 | ||
132 | //! Wakes the wake_count threads waiting on the futex pval1 and requeues up to requeue_count of the blocked threads onto another futex pval2 | |
133 | BOOST_FORCEINLINE int futex_requeue(void* pval1, void* pval2, unsigned int wake_count = 1u, unsigned int requeue_count = (~static_cast< unsigned int >(0u)) >> 1) BOOST_NOEXCEPT | |
134 | { | |
135 | return futex_invoke(pval1, FUTEX_REQUEUE, wake_count, requeue_count, pval2); | |
136 | } | |
137 | ||
138 | //! Wakes the wake_count threads waiting on the futex pval1 and requeues up to requeue_count of the blocked threads onto another futex pval2 | |
139 | BOOST_FORCEINLINE int futex_requeue_private(void* pval1, void* pval2, unsigned int wake_count = 1u, unsigned int requeue_count = (~static_cast< unsigned int >(0u)) >> 1) BOOST_NOEXCEPT | |
140 | { | |
141 | return futex_invoke(pval1, FUTEX_REQUEUE | BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG, wake_count, requeue_count, pval2); | |
142 | } | |
143 | ||
144 | } // namespace detail | |
145 | } // namespace atomics | |
146 | } // namespace boost | |
147 | ||
148 | #include <boost/atomic/detail/footer.hpp> | |
149 | ||
150 | #endif // defined(BOOST_ATOMIC_DETAIL_SYS_FUTEX) | |
151 | ||
152 | #endif // defined(__linux__) || defined(__OpenBSD__) || defined(__NETBSD__) || defined(__NetBSD__) | |
153 | ||
154 | #endif // BOOST_ATOMIC_DETAIL_FUTEX_HPP_INCLUDED_ |