1/*
2 Copyright 2005-2013 Intel Corporation. All Rights Reserved.
3
4 This file is part of Threading Building Blocks.
5
6 Threading Building Blocks is free software; you can redistribute it
7 and/or modify it under the terms of the GNU General Public License
8 version 2 as published by the Free Software Foundation.
9
10 Threading Building Blocks is distributed in the hope that it will be
11 useful, but WITHOUT ANY WARRANTY; without even the implied warranty
12 of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with Threading Building Blocks; if not, write to the Free Software
17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18
19 As a special exception, you may use this file as part of a free software
20 library without restriction. Specifically, if other files instantiate
21 templates or use macros or inline functions from this file, or you compile
22 this file and link it with other files to produce an executable, this
23 file does not by itself cause the resulting executable to be covered by
24 the GNU General Public License. This exception does not however
25 invalidate any other reasons why the executable file might be covered by
26 the GNU General Public License.
27*/
28
29#ifndef __TBB__x86_eliding_mutex_impl_H
30#define __TBB__x86_eliding_mutex_impl_H
31
32#ifndef __TBB_spin_mutex_H
33#error Do not #include this internal file directly; use public TBB headers instead.
34#endif
35
36#if ( __TBB_x86_32 || __TBB_x86_64 )
37
38namespace tbb {
39namespace interface7 {
40namespace internal {
41
42template<typename Mutex>
43class padded_mutex;
44
45//! An eliding lock that occupies a single byte.
46/** A x86_eliding_mutex is an HLE-enabled spin mutex. It is recommended to
47 put the mutex on a cache line that is not shared by the data it protects.
48 It should be used for locking short critical sections where the lock is
49 contended but the data it protects are not. If zero-initialized, the
50 mutex is considered unheld.
51 @ingroup synchronization */
52class x86_eliding_mutex {
53
54 //! 0 if lock is released, 1 if lock is acquired.
55 __TBB_atomic_flag flag;
56
57 friend class padded_mutex<x86_eliding_mutex>;
58
59public:
60 //! Construct unacquired lock.
61 /** Equivalent to zero-initialization of *this. */
62 x86_eliding_mutex() : flag(0) {}
63
64// bug in gcc 3.x.x causes syntax error in spite of the friend declaration above.
65// Make the scoped_lock public in that case.
66#if __TBB_USE_X86_ELIDING_MUTEX || __TBB_GCC_VERSION < 40000
67#else
68 // by default we will not provide the scoped_lock interface. The user
69 // should use the padded version of the mutex. scoped_lock is used in
70 // padded_mutex template.
71private:
72#endif
73 // scoped_lock in padded_mutex<> is the interface to use.
74 //! Represents acquisition of a mutex.
75 class scoped_lock : tbb::internal::no_copy {
76 private:
77 //! Points to currently held mutex, or NULL if no lock is held.
78 x86_eliding_mutex* my_mutex;
79
80 public:
81 //! Construct without acquiring a mutex.
82 scoped_lock() : my_mutex(NULL) {}
83
84 //! Construct and acquire lock on a mutex.
85 scoped_lock( x86_eliding_mutex& m ) : my_mutex(NULL) { acquire(m); }
86
87 //! Acquire lock.
88 void acquire( x86_eliding_mutex& m ) {
89 __TBB_ASSERT( !my_mutex, "already holding a lock" );
90
91 my_mutex=&m;
92 my_mutex->lock();
93 }
94
95 //! Try acquiring lock (non-blocking)
96 /** Return true if lock acquired; false otherwise. */
97 bool try_acquire( x86_eliding_mutex& m ) {
98 __TBB_ASSERT( !my_mutex, "already holding a lock" );
99
100 bool result = m.try_lock();
101 if( result ) {
102 my_mutex = &m;
103 }
104 return result;
105 }
106
107 //! Release lock
108 void release() {
109 __TBB_ASSERT( my_mutex, "release on scoped_lock that is not holding a lock" );
110
111 my_mutex->unlock();
112 my_mutex = NULL;
113 }
114
115 //! Destroy lock. If holding a lock, releases the lock first.
116 ~scoped_lock() {
117 if( my_mutex ) {
118 release();
119 }
120 }
121 };
122#if __TBB_USE_X86_ELIDING_MUTEX || __TBB_GCC_VERSION < 40000
123#else
124public:
125#endif /* __TBB_USE_X86_ELIDING_MUTEX */
126
127 // Mutex traits
128 static const bool is_rw_mutex = false;
129 static const bool is_recursive_mutex = false;
130 static const bool is_fair_mutex = false;
131
132 // ISO C++0x compatibility methods
133
134 //! Acquire lock
135 void lock() {
136 __TBB_LockByteElided(flag);
137 }
138
139 //! Try acquiring lock (non-blocking)
140 /** Return true if lock acquired; false otherwise. */
141 bool try_lock() {
142 return __TBB_TryLockByteElided(flag);
143 }
144
145 //! Release lock
146 void unlock() {
147 __TBB_UnlockByteElided( flag );
148 }
149}; // end of x86_eliding_mutex
150
151} // namespace internal
152} // namespace interface7
153} // namespace tbb
154
155#endif /* ( __TBB_x86_32 || __TBB_x86_64 ) */
156
157#endif /* __TBB__x86_eliding_mutex_impl_H */
158