boost/smart_ptr/detail/spinlock_gcc_arm.hpp

   1 #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_GCC_ARM_HPP_INCLUDED
   2 #define BOOST_SMART_PTR_DETAIL_SPINLOCK_GCC_ARM_HPP_INCLUDED
   3
   4 //
   5 //  Copyright (c) 2008, 2011 Peter Dimov
   6 //
   7 //  Distributed under the Boost Software License, Version 1.0.
   8 //  See accompanying file LICENSE_1_0.txt or copy at
   9 //  http://www.boost.org/LICENSE_1_0.txt)
  10 //
  11
  12 #include <boost/smart_ptr/detail/yield_k.hpp>
  13
  14 #if defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7EM__) || defined(__ARM_ARCH_7S__)
  15
  16 # define BOOST_SP_ARM_BARRIER "dmb"
  17 # define BOOST_SP_ARM_HAS_LDREX
  18
  19 #elif defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__) || defined(__ARM_ARCH_6T2__)
  20
  21 # define BOOST_SP_ARM_BARRIER "mcr p15, 0, r0, c7, c10, 5"
  22 # define BOOST_SP_ARM_HAS_LDREX
  23
  24 #else
  25
  26 # define BOOST_SP_ARM_BARRIER ""
  27
  28 #endif
  29
  30 namespace boost
  31 {
  32
  33 namespace detail
  34 {
  35
  36 class spinlock
  37 {
  38 public:
  39
  40     int v_;
  41
  42 public:
  43
  44     bool try_lock()
  45     {
  46         int r;
  47
  48 #ifdef BOOST_SP_ARM_HAS_LDREX
  49
  50         __asm__ __volatile__(
  51             "ldrex %0, [%2]; \n"
  52             "cmp %0, %1; \n"
  53             "strexne %0, %1, [%2]; \n"
  54             BOOST_SP_ARM_BARRIER :
  55             "=&r"( r ): // outputs
  56             "r"( 1 ), "r"( &v_ ): // inputs
  57             "memory", "cc" );
  58
  59 #else
  60
  61         __asm__ __volatile__(
  62             "swp %0, %1, [%2];\n"
  63             BOOST_SP_ARM_BARRIER :
  64             "=&r"( r ): // outputs
  65             "r"( 1 ), "r"( &v_ ): // inputs
  66             "memory", "cc" );
  67
  68 #endif
  69
  70         return r == 0;
  71     }
  72
  73     void lock()
  74     {
  75         for( unsigned k = 0; !try_lock(); ++k )
  76         {
  77             boost::detail::yield( k );
  78         }
  79     }
  80
  81     void unlock()
  82     {
  83         __asm__ __volatile__( BOOST_SP_ARM_BARRIER ::: "memory" );
  84         *const_cast< int volatile* >( &v_ ) = 0;
  85     }
  86
  87 public:
  88
  89     class scoped_lock
  90     {
  91     private:
  92
  93         spinlock & sp_;
  94
  95         scoped_lock( scoped_lock const & );
  96         scoped_lock & operator=( scoped_lock const & );
  97
  98     public:
  99
 100         explicit scoped_lock( spinlock & sp ): sp_( sp )
 101         {
 102             sp.lock();
 103         }
 104
 105         ~scoped_lock()
 106         {
 107             sp_.unlock();
 108         }
 109     };
 110 };
 111
 112 } // namespace detail
 113 } // namespace boost
 114
 115 #define BOOST_DETAIL_SPINLOCK_INIT {0}
 116
 117 #undef BOOST_SP_ARM_BARRIER
 118 #undef BOOST_SP_ARM_HAS_LDREX
 119
 120 #endif // #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_GCC_ARM_HPP_INCLUDED