| 1 | // SPDX-FileCopyrightText: 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 2 | // |
| 3 | // SPDX-License-Identifier: LGPL-2.1-or-later |
| 4 | |
| 5 | #ifndef _URCU_FUTEX_H |
| 6 | #define _URCU_FUTEX_H |
| 7 | |
| 8 | /* |
| 9 | * Userspace RCU - sys_futex/compat_futex header. |
| 10 | */ |
| 11 | |
| 12 | #include <urcu/config.h> |
| 13 | #include <urcu/syscall-compat.h> |
| 14 | |
| 15 | #include <errno.h> |
| 16 | #include <stdint.h> |
| 17 | #include <time.h> |
| 18 | |
| 19 | #if (defined(__linux__) && defined(__NR_futex)) |
| 20 | |
| 21 | /* For backwards compat */ |
| 22 | #define CONFIG_RCU_HAVE_FUTEX 1 |
| 23 | |
| 24 | #include <unistd.h> |
| 25 | #include <errno.h> |
| 26 | #include <urcu/compiler.h> |
| 27 | #include <urcu/arch.h> |
| 28 | |
| 29 | #elif defined(__FreeBSD__) |
| 30 | |
| 31 | #include <sys/types.h> |
| 32 | #include <sys/umtx.h> |
| 33 | |
| 34 | #endif |
| 35 | |
| 36 | #ifdef __cplusplus |
| 37 | extern "C" { |
| 38 | #endif |
| 39 | |
| 40 | #define FUTEX_WAIT 0 |
| 41 | #define FUTEX_WAKE 1 |
| 42 | |
| 43 | /* |
| 44 | * sys_futex compatibility header. |
| 45 | * Use *only* *either of* futex_noasync OR futex_async on a given address. |
| 46 | * |
| 47 | * futex_noasync cannot be executed in signal handlers, but ensures that |
| 48 | * it will be put in a wait queue even in compatibility mode. |
| 49 | * |
| 50 | * futex_async is signal-handler safe for the wakeup. It uses polling |
| 51 | * on the wait-side in compatibility mode. |
| 52 | * |
| 53 | * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted |
| 54 | * (returns EINTR). |
| 55 | */ |
| 56 | |
| 57 | extern int compat_futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 58 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3); |
| 59 | extern int compat_futex_async(int32_t *uaddr, int op, int32_t val, |
| 60 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3); |
| 61 | |
| 62 | #if (defined(__linux__) && defined(__NR_futex)) |
| 63 | |
| 64 | static inline int 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 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 = 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 compat_futex_async(uaddr, op, val, timeout, |
| 88 | uaddr2, val3); |
| 89 | } |
| 90 | return ret; |
| 91 | |
| 92 | } |
| 93 | |
| 94 | static inline int 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 = futex(uaddr, op, val, timeout, uaddr2, val3); |
| 100 | if (caa_unlikely(ret < 0 && errno == ENOSYS)) { |
| 101 | return compat_futex_async(uaddr, op, val, timeout, |
| 102 | uaddr2, val3); |
| 103 | } |
| 104 | return ret; |
| 105 | } |
| 106 | |
| 107 | #elif defined(__FreeBSD__) |
| 108 | |
| 109 | static inline int futex_async(int32_t *uaddr, int op, int32_t val, |
| 110 | const struct timespec *timeout, |
| 111 | int32_t *uaddr2 __attribute__((unused)), |
| 112 | int32_t val3 __attribute__((unused))) |
| 113 | { |
| 114 | int umtx_op; |
| 115 | void *umtx_uaddr = NULL, *umtx_uaddr2 = NULL; |
| 116 | struct _umtx_time umtx_timeout = { |
| 117 | ._flags = UMTX_ABSTIME, |
| 118 | ._clockid = CLOCK_MONOTONIC, |
| 119 | }; |
| 120 | |
| 121 | switch (op) { |
| 122 | case FUTEX_WAIT: |
| 123 | /* On FreeBSD, a "u_int" is a 32-bit integer. */ |
| 124 | umtx_op = UMTX_OP_WAIT_UINT; |
| 125 | if (timeout != NULL) { |
| 126 | umtx_timeout._timeout = *timeout; |
| 127 | umtx_uaddr = (void *) sizeof(umtx_timeout); |
| 128 | umtx_uaddr2 = (void *) &umtx_timeout; |
| 129 | } |
| 130 | break; |
| 131 | case FUTEX_WAKE: |
| 132 | umtx_op = UMTX_OP_WAKE; |
| 133 | break; |
| 134 | default: |
| 135 | errno = EINVAL; |
| 136 | return -1; |
| 137 | } |
| 138 | |
| 139 | return _umtx_op(uaddr, umtx_op, (uint32_t) val, umtx_uaddr, |
| 140 | umtx_uaddr2); |
| 141 | } |
| 142 | |
| 143 | static inline int futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 144 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 145 | { |
| 146 | return futex_async(uaddr, op, val, timeout, uaddr2, val3); |
| 147 | } |
| 148 | |
| 149 | #elif defined(__CYGWIN__) |
| 150 | |
| 151 | /* |
| 152 | * The futex_noasync compat code uses a weak symbol to share state across |
| 153 | * different shared object which is not possible on Windows with the |
| 154 | * Portable Executable format. Use the async compat code for both cases. |
| 155 | */ |
| 156 | static inline int futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 157 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 158 | { |
| 159 | return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); |
| 160 | } |
| 161 | |
| 162 | static inline int futex_async(int32_t *uaddr, int op, int32_t val, |
| 163 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 164 | { |
| 165 | return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); |
| 166 | } |
| 167 | |
| 168 | #else |
| 169 | |
| 170 | static inline int futex_noasync(int32_t *uaddr, int op, int32_t val, |
| 171 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 172 | { |
| 173 | return compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3); |
| 174 | } |
| 175 | |
| 176 | static inline int futex_async(int32_t *uaddr, int op, int32_t val, |
| 177 | const struct timespec *timeout, int32_t *uaddr2, int32_t val3) |
| 178 | { |
| 179 | return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3); |
| 180 | } |
| 181 | |
| 182 | #endif |
| 183 | |
| 184 | #ifdef __cplusplus |
| 185 | } |
| 186 | #endif |
| 187 | |
| 188 | #endif /* _URCU_FUTEX_H */ |