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(BOOST_SP_REPORT_IMPLEMENTATION)
15 
16 #include <boost/config/pragma_message.hpp>
17 BOOST_PRAGMA_MESSAGE("Using g++/ARM spinlock")
18 
19 #endif
20 
21 #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__)
22 
23 # define BOOST_SP_ARM_BARRIER "dmb"
24 # define BOOST_SP_ARM_HAS_LDREX
25 
26 #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__)
27 
28 # define BOOST_SP_ARM_BARRIER "mcr p15, 0, r0, c7, c10, 5"
29 # define BOOST_SP_ARM_HAS_LDREX
30 
31 #else
32 
33 # define BOOST_SP_ARM_BARRIER ""
34 
35 #endif
36 
37 namespace boost
38 {
39 
40 namespace detail
41 {
42 
43 class spinlock
44 {
45 public:
46 
47     int v_;
48 
49 public:
50 
try_lock()51     bool try_lock()
52     {
53         int r;
54 
55 #ifdef BOOST_SP_ARM_HAS_LDREX
56 
57         __asm__ __volatile__(
58             "ldrex %0, [%2]; \n"
59             "cmp %0, %1; \n"
60             "strexne %0, %1, [%2]; \n"
61             BOOST_SP_ARM_BARRIER :
62             "=&r"( r ): // outputs
63             "r"( 1 ), "r"( &v_ ): // inputs
64             "memory", "cc" );
65 
66 #else
67 
68         __asm__ __volatile__(
69             "swp %0, %1, [%2];\n"
70             BOOST_SP_ARM_BARRIER :
71             "=&r"( r ): // outputs
72             "r"( 1 ), "r"( &v_ ): // inputs
73             "memory", "cc" );
74 
75 #endif
76 
77         return r == 0;
78     }
79 
lock()80     void lock()
81     {
82         for( unsigned k = 0; !try_lock(); ++k )
83         {
84             boost::detail::yield( k );
85         }
86     }
87 
unlock()88     void unlock()
89     {
90         __asm__ __volatile__( BOOST_SP_ARM_BARRIER ::: "memory" );
91         *const_cast< int volatile* >( &v_ ) = 0;
92         __asm__ __volatile__( BOOST_SP_ARM_BARRIER ::: "memory" );
93     }
94 
95 public:
96 
97     class scoped_lock
98     {
99     private:
100 
101         spinlock & sp_;
102 
103         scoped_lock( scoped_lock const & );
104         scoped_lock & operator=( scoped_lock const & );
105 
106     public:
107 
scoped_lock(spinlock & sp)108         explicit scoped_lock( spinlock & sp ): sp_( sp )
109         {
110             sp.lock();
111         }
112 
~scoped_lock()113         ~scoped_lock()
114         {
115             sp_.unlock();
116         }
117     };
118 };
119 
120 } // namespace detail
121 } // namespace boost
122 
123 #define BOOST_DETAIL_SPINLOCK_INIT {0}
124 
125 #undef BOOST_SP_ARM_BARRIER
126 #undef BOOST_SP_ARM_HAS_LDREX
127 
128 #endif // #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_GCC_ARM_HPP_INCLUDED
129