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 <stdint.h>
  28
  29 #ifdef __cplusplus
  30 extern "C" {
  31 #endif
  32
  33 #define FUTEX_WAIT              0
  34 #define FUTEX_WAKE              1
  35
  36 /*
  37  * sys_futex compatibility header.
  38  * Use *only* *either of* futex_noasync OR futex_async on a given address.
  39  *
  40  * futex_noasync cannot be executed in signal handlers, but ensures that
  41  * it will be put in a wait queue even in compatibility mode.
  42  *
  43  * futex_async is signal-handler safe for the wakeup. It uses polling
  44  * on the wait-side in compatibility mode.
  45  *
  46  * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted
  47  * (returns EINTR).
  48  */
  49
  50 extern int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
  51                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
  52 extern int compat_futex_async(int32_t *uaddr, int op, int32_t val,
  53                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
  54
  55 #ifdef CONFIG_RCU_HAVE_FUTEX
  56
  57 #include <unistd.h>
  58 #include <errno.h>
  59 #include <urcu/compiler.h>
  60 #include <urcu/arch.h>
  61
  62 static inline int futex(int32_t *uaddr, int op, int32_t val,
  63                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
  64 {
  65         return syscall(__NR_futex, uaddr, op, val, timeout,
  66                         uaddr2, val3);
  67 }
  68
  69 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
  70                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
  71 {
  72         int ret;
  73
  74         ret = futex(uaddr, op, val, timeout, uaddr2, val3);
  75         if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
  76                 return compat_futex_noasync(uaddr, op, val, timeout,
  77                                 uaddr2, val3);
  78         }
  79         return ret;
  80
  81 }
  82
  83 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
  84                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
  85 {
  86         int ret;
  87
  88         ret = futex(uaddr, op, val, timeout, uaddr2, val3);
  89         if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
  90                 return compat_futex_async(uaddr, op, val, timeout,
  91                                 uaddr2, val3);
  92         }
  93         return ret;
  94 }
  95
  96 #else
  97
  98 static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
  99                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 100 {
 101         return compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3);
 102 }
 103
 104 static inline int futex_async(int32_t *uaddr, int op, int32_t val,
 105                 const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 106 {
 107         return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
 108 }
 109
 110 #endif
 111
 112 #ifdef __cplusplus
 113 }
 114 #endif
 115
 116 #endif /* _URCU_FUTEX_H */