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 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 namespace boost
  15 {
  16
  17 namespace detail
  18 {
  19
  20 class spinlock
  21 {
  22 public:
  23
  24     int v_;
  25
  26 public:
  27
  28     bool try_lock()
  29     {
  30         int r;
  31
  32         __asm__ __volatile__(
  33             "swp %0, %1, [%2]":
  34             "=&r"( r ): // outputs
  35             "r"( 1 ), "r"( &v_ ): // inputs
  36             "memory", "cc" );
  37
  38         return r == 0;
  39     }
  40
  41     void lock()
  42     {
  43         for( unsigned k = 0; !try_lock(); ++k )
  44         {
  45             boost::detail::yield( k );
  46         }
  47     }
  48
  49     void unlock()
  50     {
  51         __asm__ __volatile__( "" ::: "memory" );
  52         *const_cast< int volatile* >( &v_ ) = 0;
  53     }
  54
  55 public:
  56
  57     class scoped_lock
  58     {
  59     private:
  60
  61         spinlock & sp_;
  62
  63         scoped_lock( scoped_lock const & );
  64         scoped_lock & operator=( scoped_lock const & );
  65
  66     public:
  67
  68         explicit scoped_lock( spinlock & sp ): sp_( sp )
  69         {
  70             sp.lock();
  71         }
  72
  73         ~scoped_lock()
  74         {
  75             sp_.unlock();
  76         }
  77     };
  78 };
  79
  80 } // namespace detail
  81 } // namespace boost
  82
  83 #define BOOST_DETAIL_SPINLOCK_INIT {0}
  84
  85 #endif // #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_GCC_ARM_HPP_INCLUDED