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1 : //===- llvm/Support/Mutex.h - Mutex Operating System Concept -----*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 : //
10 : // This file declares the llvm::sys::Mutex class.
11 : //
12 : //===----------------------------------------------------------------------===//
13 :
14 : #ifndef LLVM_SUPPORT_MUTEX_H
15 : #define LLVM_SUPPORT_MUTEX_H
16 :
17 : #include "llvm/Config/llvm-config.h"
18 : #include "llvm/Support/Compiler.h"
19 : #include "llvm/Support/Threading.h"
20 : #include <cassert>
21 :
22 : namespace llvm
23 : {
24 : namespace sys
25 : {
26 : /// Platform agnostic Mutex class.
27 : class MutexImpl
28 : {
29 : /// @name Constructors
30 : /// @{
31 : public:
32 :
33 : /// Initializes the lock but doesn't acquire it. if \p recursive is set
34 : /// to false, the lock will not be recursive which makes it cheaper but
35 : /// also more likely to deadlock (same thread can't acquire more than
36 : /// once).
37 : /// Default Constructor.
38 : explicit MutexImpl(bool recursive = true);
39 :
40 : /// Releases and removes the lock
41 : /// Destructor
42 : ~MutexImpl();
43 :
44 : /// @}
45 : /// @name Methods
46 : /// @{
47 : public:
48 :
49 : /// Attempts to unconditionally acquire the lock. If the lock is held by
50 : /// another thread, this method will wait until it can acquire the lock.
51 : /// @returns false if any kind of error occurs, true otherwise.
52 : /// Unconditionally acquire the lock.
53 : bool acquire();
54 :
55 : /// Attempts to release the lock. If the lock is held by the current
56 : /// thread, the lock is released allowing other threads to acquire the
57 : /// lock.
58 : /// @returns false if any kind of error occurs, true otherwise.
59 : /// Unconditionally release the lock.
60 : bool release();
61 :
62 : /// Attempts to acquire the lock without blocking. If the lock is not
63 : /// available, this function returns false quickly (without blocking). If
64 : /// the lock is available, it is acquired.
65 : /// @returns false if any kind of error occurs or the lock is not
66 : /// available, true otherwise.
67 : /// Try to acquire the lock.
68 : bool tryacquire();
69 :
70 : //@}
71 : /// @name Platform Dependent Data
72 : /// @{
73 : private:
74 : #if defined(LLVM_ENABLE_THREADS) && LLVM_ENABLE_THREADS != 0
75 : void* data_; ///< We don't know what the data will be
76 : #endif
77 :
78 : /// @}
79 : /// @name Do Not Implement
80 : /// @{
81 : private:
82 : MutexImpl(const MutexImpl &) = delete;
83 : void operator=(const MutexImpl &) = delete;
84 : /// @}
85 : };
86 :
87 :
88 : /// SmartMutex - A mutex with a compile time constant parameter that
89 : /// indicates whether this mutex should become a no-op when we're not
90 : /// running in multithreaded mode.
91 : template<bool mt_only>
92 224658 : class SmartMutex {
93 : MutexImpl impl;
94 : unsigned acquired;
95 : bool recursive;
96 : public:
97 417058 : explicit SmartMutex(bool rec = true) :
98 417058 : impl(rec), acquired(0), recursive(rec) { }
99 :
100 646947 : bool lock() {
101 646947 : if (!mt_only || llvm_is_multithreaded()) {
102 2181186 : return impl.acquire();
103 : } else {
104 : // Single-threaded debugging code. This would be racy in
105 : // multithreaded mode, but provides not sanity checks in single
106 : // threaded mode.
107 : assert((recursive || acquired == 0) && "Lock already acquired!!");
108 0 : ++acquired;
109 0 : return true;
110 : }
111 : }
112 :
113 646947 : bool unlock() {
114 646947 : if (!mt_only || llvm_is_multithreaded()) {
115 2181186 : return impl.release();
116 : } else {
117 : // Single-threaded debugging code. This would be racy in
118 : // multithreaded mode, but provides not sanity checks in single
119 : // threaded mode.
120 : assert(((recursive && acquired) || (acquired == 1)) &&
121 : "Lock not acquired before release!");
122 0 : --acquired;
123 0 : return true;
124 : }
125 : }
126 :
127 : bool try_lock() {
128 : if (!mt_only || llvm_is_multithreaded())
129 0 : return impl.tryacquire();
130 : else return true;
131 : }
132 :
133 : private:
134 : SmartMutex(const SmartMutex<mt_only> & original);
135 : void operator=(const SmartMutex<mt_only> &);
136 : };
137 :
138 : /// Mutex - A standard, always enforced mutex.
139 : typedef SmartMutex<false> Mutex;
140 :
141 : template<bool mt_only>
142 : class SmartScopedLock {
143 : SmartMutex<mt_only>& mtx;
144 :
145 : public:
146 : SmartScopedLock(SmartMutex<mt_only>& m) : mtx(m) {
147 646947 : mtx.lock();
148 : }
149 :
150 : ~SmartScopedLock() {
151 646947 : mtx.unlock();
152 : }
153 : };
154 :
155 : typedef SmartScopedLock<false> ScopedLock;
156 : }
157 : }
158 :
159 : #endif
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