uspace/lib/c/include/barrier.h

   1 /*
   2  * Copyright (c) 2012 Adam Hraska
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * - Redistributions of source code must retain the above copyright
  10  *   notice, this list of conditions and the following disclaimer.
  11  * - Redistributions in binary form must reproduce the above copyright
  12  *   notice, this list of conditions and the following disclaimer in the
  13  *   documentation and/or other materials provided with the distribution.
  14  * - The name of the author may not be used to endorse or promote products
  15  *   derived from this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /** @addtogroup libc
  30  * @{
  31  */
  32 /** @file
  33  */
  34
  35 #ifndef _LIBC_COMPILER_BARRIER_H_
  36 #define _LIBC_COMPILER_BARRIER_H_
  37
  38 #include <stdatomic.h>
  39
  40 static inline void compiler_barrier(void)
  41 {
  42         atomic_signal_fence(memory_order_seq_cst);
  43 }
  44
  45 static inline void memory_barrier(void)
  46 {
  47         atomic_thread_fence(memory_order_seq_cst);
  48 }
  49
  50 static inline void read_barrier(void)
  51 {
  52         atomic_thread_fence(memory_order_acquire);
  53 }
  54
  55 static inline void write_barrier(void)
  56 {
  57         atomic_thread_fence(memory_order_release);
  58 }
  59
  60 /** Forces the compiler to access (ie load/store) the variable only once. */
  61 #define ACCESS_ONCE(var) (*((volatile typeof(var)*)&(var)))
  62
  63 #endif /* _LIBC_COMPILER_BARRIER_H_ */