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 __cplusplus
  32 extern "C" {
  33 #endif
  34
  35 #define FUTEX_WAIT              0
  36 #define FUTEX_WAKE              1
  37
  38 /*
  39  * sys_futex compatibility header.
  40  * Use *only* *either of* futex_noasync OR futex_async on a given address.
  41  *
  42  * futex_noasync cannot be executed in signal handlers, but ensures that
  43  * it will be put in a wait queue even in compatibility mode.
  44  *
  45  * futex_async is signal-handler safe for the wakeup. It uses polling
  46  * on the wait-side in compatibility mode.
  47  *
  48  * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted
  49  * (returns EINTR).
  50  */
  51
  52 extern int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
  53                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
  54 extern int compat_futex_async(int32_t *uaddr, int op, int32_t val,
  55                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
  56
  57 #ifdef CONFIG_RCU_HAVE_FUTEX
  58
  59 #include <unistd.h>
  60 #include <errno.h>
  61 #include <urcu/compiler.h>
  62 #include <urcu/arch.h>
  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 #include <sys/types.h>
 110 #include <sys/umtx.h>
 111
 112 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
 113                 const struct timespec *timeout,
 114                 int32_t *uaddr2 __attribute__((unused)),
 115                 int32_t val3 __attribute__((unused)))
 116 {
 117         int umtx_op;
 118         void *umtx_uaddr = NULL, *umtx_uaddr2 = NULL;
 119         struct _umtx_time umtx_timeout = {
 120                 ._flags = UMTX_ABSTIME,
 121                 ._clockid = CLOCK_MONOTONIC,
 122         };
 123
 124         switch (op) {
 125         case FUTEX_WAIT:
 126                 /* On FreeBSD, a "u_int" is a 32-bit integer. */
 127                 umtx_op = UMTX_OP_WAIT_UINT;
 128                 if (timeout != NULL) {
 129                         umtx_timeout._timeout = *timeout;
 130                         umtx_uaddr = (void *) sizeof(umtx_timeout);
 131                         umtx_uaddr2 = (void *) &umtx_timeout;
 132                 }
 133                 break;
 134         case FUTEX_WAKE:
 135                 umtx_op = UMTX_OP_WAKE;
 136                 break;
 137         default:
 138                 errno = EINVAL;
 139                 return -1;
 140         }
 141
 142         return _umtx_op(uaddr, umtx_op, (uint32_t) val, umtx_uaddr,
 143                         umtx_uaddr2);
 144 }
 145
 146 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
 147                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 148 {
 149         return futex_async(uaddr, op, val, timeout, uaddr2, val3);
 150 }
 151
 152 #elif defined(__CYGWIN__)
 153
 154 /*
 155  * The futex_noasync compat code uses a weak symbol to share state across
 156  * different shared object which is not possible on Windows with the
 157  * Portable Executable format. Use the async compat code for both cases.
 158  */
 159 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
 160                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 161 {
 162         return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
 163 }
 164
 165 static inline int futex_async(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 #else
 172
 173 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
 174                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 175 {
 176         return compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3);
 177 }
 178
 179 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
 180                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 181 {
 182         return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
 183 }
 184
 185 #endif
 186
 187 #ifdef __cplusplus
 188 }
 189 #endif
 190
 191 #endif /* _URCU_FUTEX_H */