aboutsummaryrefslogtreecommitdiff
path: root/gold/gold-threads.h
blob: 1e4bffaba014fd21eb0394299a285f5c282c6469 (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
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
// gold-threads.h -- thread support for gold  -*- C++ -*-

// Copyright (C) 2006-2024 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of gold.

// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.

// gold can be configured to support threads.  If threads are
// supported, the user can specify at runtime whether or not to
// support them.  This provides an interface to manage locking
// accordingly.

// Lock
//   A simple lock class.

#ifndef GOLD_THREADS_H
#define GOLD_THREADS_H

namespace gold
{

class Condvar;
class Once_initialize;
class Initialize_lock_once;

// The interface for the implementation of a Lock.

class Lock_impl
{
 public:
  Lock_impl()
  { }

  virtual
  ~Lock_impl()
  { }

  virtual void
  acquire() = 0;

  virtual void
  release() = 0;
};

// A simple lock class.

class Lock
{
 public:
  Lock();

  ~Lock();

  // Acquire the lock.
  void
  acquire()
  { this->lock_->acquire(); }

  // Release the lock.
  void
  release()
  { this->lock_->release(); }

 private:
  // This class can not be copied.
  Lock(const Lock&);
  Lock& operator=(const Lock&);

  friend class Condvar;
  Lock_impl*
  get_impl() const
  { return this->lock_; }

  Lock_impl* lock_;
};

// RAII for Lock.

class Hold_lock
{
 public:
  Hold_lock(Lock& lock)
    : lock_(lock)
  { this->lock_.acquire(); }

  ~Hold_lock()
  { this->lock_.release(); }

 private:
  // This class can not be copied.
  Hold_lock(const Hold_lock&);
  Hold_lock& operator=(const Hold_lock&);

  Lock& lock_;
};

class Hold_optional_lock
{
 public:
  Hold_optional_lock(Lock* lock)
    : lock_(lock)
  {
    if (this->lock_ != NULL)
      this->lock_->acquire();
  }

  ~Hold_optional_lock()
  {
    if (this->lock_ != NULL)
      this->lock_->release();
  }

 private:
  Hold_optional_lock(const Hold_optional_lock&);
  Hold_optional_lock& operator=(const Hold_optional_lock&);

  Lock* lock_;
};

// The interface for the implementation of a condition variable.

class Condvar_impl
{
 public:
  Condvar_impl()
  { }

  virtual
  ~Condvar_impl()
  { }

  virtual void
  wait(Lock_impl*) = 0;

  virtual void
  signal() = 0;

  virtual void
  broadcast() = 0;
};

// A simple condition variable class.  It is always associated with a
// specific lock.

class Condvar
{
 public:
  Condvar(Lock& lock);
  ~Condvar();

  // Wait for the condition variable to be signalled.  This should
  // only be called when the lock is held.
  void
  wait()
  { this->condvar_->wait(this->lock_.get_impl()); }

  // Signal the condition variable--wake up at least one thread
  // waiting on the condition variable.  This should only be called
  // when the lock is held.
  void
  signal()
  { this->condvar_->signal(); }

  // Broadcast the condition variable--wake up all threads waiting on
  // the condition variable.  This should only be called when the lock
  // is held.
  void
  broadcast()
  { this->condvar_->broadcast(); }

 private:
  // This class can not be copied.
  Condvar(const Condvar&);
  Condvar& operator=(const Condvar&);

  Lock& lock_;
  Condvar_impl* condvar_;
};

// A class used to do something once.  This is an abstract parent
// class; any actual use will involve a child of this.

class Once
{
 public:
  Once();

  virtual
  ~Once()
  { }

  // Call this function to do whatever it is.  We pass an argument
  // even though you have to use a child class because in some uses
  // setting the argument would itself require a Once class.
  void
  run_once(void* arg);

  // This is an internal function, which must be public because it is
  // run by an extern "C" function called via pthread_once.
  void
  internal_run(void* arg);

 protected:
  // This must be implemented by the child class.
  virtual void
  do_run_once(void* arg) = 0;

 private:
  // True if we have already run the function.
  bool was_run_;
#if defined(ENABLE_THREADS) && defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
  // Internal compare-and-swap lock on was_run_;
  uint32_t was_run_lock_;
#endif
  // The lock to run the function only once.
  Once_initialize* once_;
};

// A class used to initialize a lock exactly once, after the options
// have been read.  This is needed because the implementation of locks
// depends on whether we've seen the --threads option.  Before the
// options have been read, we know we are single-threaded, so we can
// get by without using a lock.  This class should be an instance
// variable of the class which has a lock which needs to be
// initialized.

class Initialize_lock : public Once
{
 public:
  // The class which uses this will have a pointer to a lock.  This
  // must be constructed with a pointer to that pointer.
  Initialize_lock(Lock** pplock)
    : pplock_(pplock)
  { }

  // Initialize the lock.  Return true if the lock is now initialized,
  // false if it is not (because the options have not yet been read).
  bool
  initialize();

 protected:
  void
  do_run_once(void*);

 private:
  // A pointer to the lock pointer which must be initialized.
  Lock** const pplock_;
};

} // End namespace gold.

#endif // !defined(GOLD_THREADS_H)