aboutsummaryrefslogtreecommitdiffstats
path: root/include/llvm/System/Mutex.h
blob: 71d10067c303442ffda43d857709106c9fb88f77 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
//===- llvm/System/Mutex.h - Mutex Operating System Concept -----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the llvm::sys::Mutex class.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SYSTEM_MUTEX_H
#define LLVM_SYSTEM_MUTEX_H

#include "llvm/System/Threading.h"
#include <cassert>

namespace llvm
{
  namespace sys
  {
    /// @brief Platform agnostic Mutex class.
    class MutexImpl
    {
    /// @name Constructors
    /// @{
    public:

      /// Initializes the lock but doesn't acquire it. if \p recursive is set
      /// to false, the lock will not be recursive which makes it cheaper but
      /// also more likely to deadlock (same thread can't acquire more than
      /// once).
      /// @brief Default Constructor.
      explicit MutexImpl(bool recursive = true);

      /// Releases and removes the lock
      /// @brief Destructor
      ~MutexImpl();

    /// @}
    /// @name Methods
    /// @{
    public:

      /// Attempts to unconditionally acquire the lock. If the lock is held by
      /// another thread, this method will wait until it can acquire the lock.
      /// @returns false if any kind of error occurs, true otherwise.
      /// @brief Unconditionally acquire the lock.
      bool acquire();

      /// Attempts to release the lock. If the lock is held by the current
      /// thread, the lock is released allowing other threads to acquire the
      /// lock.
      /// @returns false if any kind of error occurs, true otherwise.
      /// @brief Unconditionally release the lock.
      bool release();

      /// Attempts to acquire the lock without blocking. If the lock is not
      /// available, this function returns false quickly (without blocking). If
      /// the lock is available, it is acquired.
      /// @returns false if any kind of error occurs or the lock is not
      /// available, true otherwise.
      /// @brief Try to acquire the lock.
      bool tryacquire();

    //@}
    /// @name Platform Dependent Data
    /// @{
    private:
      void* data_; ///< We don't know what the data will be

    /// @}
    /// @name Do Not Implement
    /// @{
    private:
      MutexImpl(const MutexImpl & original);
      void operator=(const MutexImpl &);
    /// @}
    };
    
    
    /// SmartMutex - A mutex with a compile time constant parameter that 
    /// indicates whether this mutex should become a no-op when we're not
    /// running in multithreaded mode.
    template<bool mt_only>
    class SmartMutex : public MutexImpl {
      unsigned acquired;
      bool recursive;
    public:
      explicit SmartMutex(bool rec = true) :
        MutexImpl(rec), acquired(0), recursive(rec) { }
      
      bool acquire() {
        if (!mt_only || llvm_is_multithreaded()) {
          return MutexImpl::acquire();
        } else {
          // Single-threaded debugging code.  This would be racy in
          // multithreaded mode, but provides not sanity checks in single
          // threaded mode.
          assert((recursive || acquired == 0) && "Lock already acquired!!");
          ++acquired;
          return true;
        }
      }

      bool release() {
        if (!mt_only || llvm_is_multithreaded()) {
          return MutexImpl::release();
        } else {
          // Single-threaded debugging code.  This would be racy in
          // multithreaded mode, but provides not sanity checks in single
          // threaded mode.
          assert(((recursive && acquired) || (acquired == 1)) &&
                 "Lock not acquired before release!");
          --acquired;
          return true;
        }
      }

      bool tryacquire() {
        if (!mt_only || llvm_is_multithreaded())
          return MutexImpl::tryacquire();
        else return true;
      }
      
      private:
        SmartMutex(const SmartMutex<mt_only> & original);
        void operator=(const SmartMutex<mt_only> &);
    };
    
    /// Mutex - A standard, always enforced mutex.
    typedef SmartMutex<false> Mutex;
    
    template<bool mt_only>
    class SmartScopedLock  {
      SmartMutex<mt_only>& mtx;
      
    public:
      SmartScopedLock(SmartMutex<mt_only>& m) : mtx(m) {
        mtx.acquire();
      }
      
      ~SmartScopedLock() {
        mtx.release();
      }
    };
    
    typedef SmartScopedLock<false> ScopedLock;
  }
}

#endif