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 */