include/urcu/uatomic/arm.h

   1 #ifndef _URCU_ARCH_UATOMIC_ARM_H
   2 #define _URCU_ARCH_UATOMIC_ARM_H
   3
   4 /*
   5  * Atomics for ARM.  This approach is usable on kernels back to 2.6.15.
   6  *
   7  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   8  * Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
   9  * Copyright (c) 1999-2004 Hewlett-Packard Development Company, L.P.
  10  * Copyright (c) 2009      Mathieu Desnoyers
  11  * Copyright (c) 2010      Paul E. McKenney, IBM Corporation
  12  *                         (Adapted from uatomic_arch_ppc.h)
  13  *
  14  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
  15  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
  16  *
  17  * Permission is hereby granted to use or copy this program
  18  * for any purpose,  provided the above notices are retained on all copies.
  19  * Permission to modify the code and to distribute modified code is granted,
  20  * provided the above notices are retained, and a notice that the code was
  21  * modified is included with the above copyright notice.
  22  *
  23  * Code inspired from libuatomic_ops-1.2, inherited in part from the
  24  * Boehm-Demers-Weiser conservative garbage collector.
  25  */
  26
  27 #include <urcu/compiler.h>
  28 #include <urcu/system.h>
  29 #include <urcu/arch.h>
  30
  31 #ifdef __cplusplus
  32 extern "C" {
  33 #endif
  34
  35 /* xchg */
  36
  37 /*
  38  * Based on [1], __sync_lock_test_and_set() is not a full barrier, but
  39  * instead only an acquire barrier. Given that uatomic_xchg() acts as
  40  * both release and acquire barriers, we therefore need to have our own
  41  * release barrier before this operation.
  42  *
  43  * [1] https://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html
  44  */
  45 #define uatomic_xchg(addr, v)                           \
  46         ({                                              \
  47                 cmm_smp_mb();                           \
  48                 __sync_lock_test_and_set(addr, v);      \
  49         })
  50
  51 #ifdef __cplusplus
  52 }
  53 #endif
  54
  55 #include <urcu/uatomic/generic.h>
  56
  57 #endif /* _URCU_ARCH_UATOMIC_ARM_H */