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 <errno.h>
  28 #include <stdint.h>
  29 #include <time.h>
  30
  31 #ifdef CONFIG_RCU_HAVE_FUTEX
  32
  33 #include <unistd.h>
  34 #include <errno.h>
  35 #include <urcu/compiler.h>
  36 #include <urcu/arch.h>
  37
  38 #elif defined(__FreeBSD__)
  39
  40 #include <sys/types.h>
  41 #include <sys/umtx.h>
  42
  43 #endif
  44
  45 #ifdef __cplusplus
  46 extern "C" {
  47 #endif
  48
  49 #define FUTEX_WAIT              0
  50 #define FUTEX_WAKE              1
  51
  52 /*
  53  * sys_futex compatibility header.
  54  * Use *only* *either of* futex_noasync OR futex_async on a given address.
  55  *
  56  * futex_noasync cannot be executed in signal handlers, but ensures that
  57  * it will be put in a wait queue even in compatibility mode.
  58  *
  59  * futex_async is signal-handler safe for the wakeup. It uses polling
  60  * on the wait-side in compatibility mode.
  61  *
  62  * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted
  63  * (returns EINTR).
  64  */
  65
  66 extern int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
  67                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
  68 extern int compat_futex_async(int32_t *uaddr, int op, int32_t val,
  69                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
  70
  71 #ifdef CONFIG_RCU_HAVE_FUTEX
  72
  73 static inline int futex(int32_t *uaddr, int op, int32_t val,
  74                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
  75 {
  76         return syscall(__NR_futex, uaddr, op, val, timeout,
  77                         uaddr2, val3);
  78 }
  79
  80 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
  81                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
  82 {
  83         int ret;
  84
  85         ret = futex(uaddr, op, val, timeout, uaddr2, val3);
  86         if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
  87                 /*
  88                  * The fallback on ENOSYS is the async-safe version of
  89                  * the compat futex implementation, because the
  90                  * async-safe compat implementation allows being used
  91                  * concurrently with calls to futex(). Indeed, sys_futex
  92                  * FUTEX_WAIT, on some architectures (mips and parisc),
  93                  * within a given process, spuriously return ENOSYS due
  94                  * to signal restart bugs on some kernel versions.
  95                  */
  96                 return compat_futex_async(uaddr, op, val, timeout,
  97                                 uaddr2, val3);
  98         }
  99         return ret;
 100
 101 }
 102
 103 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
 104                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 105 {
 106         int ret;
 107
 108         ret = futex(uaddr, op, val, timeout, uaddr2, val3);
 109         if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
 110                 return compat_futex_async(uaddr, op, val, timeout,
 111                                 uaddr2, val3);
 112         }
 113         return ret;
 114 }
 115
 116 #elif defined(__FreeBSD__)
 117
 118 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
 119                 const struct timespec *timeout,
 120                 int32_t *uaddr2 __attribute__((unused)),
 121                 int32_t val3 __attribute__((unused)))
 122 {
 123         int umtx_op;
 124         void *umtx_uaddr = NULL, *umtx_uaddr2 = NULL;
 125         struct _umtx_time umtx_timeout = {
 126                 ._flags = UMTX_ABSTIME,
 127                 ._clockid = CLOCK_MONOTONIC,
 128         };
 129
 130         switch (op) {
 131         case FUTEX_WAIT:
 132                 /* On FreeBSD, a "u_int" is a 32-bit integer. */
 133                 umtx_op = UMTX_OP_WAIT_UINT;
 134                 if (timeout != NULL) {
 135                         umtx_timeout._timeout = *timeout;
 136                         umtx_uaddr = (void *) sizeof(umtx_timeout);
 137                         umtx_uaddr2 = (void *) &umtx_timeout;
 138                 }
 139                 break;
 140         case FUTEX_WAKE:
 141                 umtx_op = UMTX_OP_WAKE;
 142                 break;
 143         default:
 144                 errno = EINVAL;
 145                 return -1;
 146         }
 147
 148         return _umtx_op(uaddr, umtx_op, (uint32_t) val, umtx_uaddr,
 149                         umtx_uaddr2);
 150 }
 151
 152 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
 153                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 154 {
 155         return futex_async(uaddr, op, val, timeout, uaddr2, val3);
 156 }
 157
 158 #elif defined(__CYGWIN__)
 159
 160 /*
 161  * The futex_noasync compat code uses a weak symbol to share state across
 162  * different shared object which is not possible on Windows with the
 163  * Portable Executable format. Use the async compat code for both cases.
 164  */
 165 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
 166                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 167 {
 168         return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
 169 }
 170
 171 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
 172                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 173 {
 174         return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
 175 }
 176
 177 #else
 178
 179 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
 180                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 181 {
 182         return compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3);
 183 }
 184
 185 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
 186                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 187 {
 188         return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
 189 }
 190
 191 #endif
 192
 193 #ifdef __cplusplus
 194 }
 195 #endif
 196
 197 #endif /* _URCU_FUTEX_H */