OpenCores
URL https://opencores.org/ocsvn/openrisc_me/openrisc_me/trunk

Subversion Repositories openrisc_me

[/] [openrisc/] [trunk/] [gnu-src/] [binutils-2.20.1/] [gold/] [token.h] - Blame information for rev 280

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 205 julius
// token.h -- lock tokens for gold   -*- C++ -*-
2
 
3
// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
4
// Written by Ian Lance Taylor <iant@google.com>.
5
 
6
// This file is part of gold.
7
 
8
// This program is free software; you can redistribute it and/or modify
9
// it under the terms of the GNU General Public License as published by
10
// the Free Software Foundation; either version 3 of the License, or
11
// (at your option) any later version.
12
 
13
// This program is distributed in the hope that it will be useful,
14
// but WITHOUT ANY WARRANTY; without even the implied warranty of
15
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16
// GNU General Public License for more details.
17
 
18
// You should have received a copy of the GNU General Public License
19
// along with this program; if not, write to the Free Software
20
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21
// MA 02110-1301, USA.
22
 
23
#ifndef GOLD_TOKEN_H
24
#define GOLD_TOKEN_H
25
 
26
namespace gold
27
{
28
 
29
class Condvar;
30
class Task;
31
 
32
// A list of Tasks, managed through the next_locked_ field in the
33
// class Task.  We define this class here because we need it in
34
// Task_token.
35
 
36
class Task_list
37
{
38
 public:
39
  Task_list()
40
    : head_(NULL), tail_(NULL)
41
  { }
42
 
43
  ~Task_list()
44
  { gold_assert(this->head_ == NULL && this->tail_ == NULL); }
45
 
46
  // Return whether the list is empty.
47
  bool
48
  empty() const
49
  { return this->head_ == NULL; }
50
 
51
  // Add T to the head of the list.
52
  void
53
  push_front(Task* t);
54
 
55
  // Add T to the end of the list.
56
  void
57
  push_back(Task* t);
58
 
59
  // Remove the first Task on the list and return it.  Return NULL if
60
  // the list is empty.
61
  Task*
62
  pop_front();
63
 
64
 private:
65
  // The start of the list.  NULL if the list is empty.
66
  Task* head_;
67
  // The end of the list.  NULL if the list is empty.
68
  Task* tail_;
69
};
70
 
71
// We support two basic types of locks, which are both implemented
72
// using the single class Task_token.
73
 
74
// A write lock may be held by a single Task at a time.  This is used
75
// to control access to a single shared resource such as an Object.
76
 
77
// A blocker is used to indicate that a Task A must be run after some
78
// set of Tasks B.  For each of the Tasks B, we increment the blocker
79
// when the Task is created, and decrement it when the Task is
80
// completed.  When the count goes to 0, the task A is ready to run.
81
 
82
// There are no shared read locks.  We always read and write objects
83
// in predictable patterns.  The purpose of the locks is to permit
84
// some flexibility for the threading system, for cases where the
85
// execution order does not matter.
86
 
87
// These tokens are only manipulated when the workqueue lock is held
88
// or when they are first created.  They do not require any locking
89
// themselves.
90
 
91
class Task_token
92
{
93
 public:
94
  Task_token(bool is_blocker)
95
    : is_blocker_(is_blocker), blockers_(0), writer_(NULL), waiting_()
96
  { }
97
 
98
  ~Task_token()
99
  {
100
    gold_assert(this->blockers_ == 0);
101
    gold_assert(this->writer_ == NULL);
102
  }
103
 
104
  // Return whether this is a blocker.
105
  bool
106
  is_blocker() const
107
  { return this->is_blocker_; }
108
 
109
  // A write lock token uses these methods.
110
 
111
  // Is the token writable?
112
  bool
113
  is_writable() const
114
  {
115
    gold_assert(!this->is_blocker_);
116
    return this->writer_ == NULL;
117
  }
118
 
119
  // Add the task as the token's writer (there may only be one
120
  // writer).
121
  void
122
  add_writer(const Task* t)
123
  {
124
    gold_assert(!this->is_blocker_ && this->writer_ == NULL);
125
    this->writer_ = t;
126
  }
127
 
128
  // Remove the task as the token's writer.
129
  void
130
  remove_writer(const Task* t)
131
  {
132
    gold_assert(!this->is_blocker_ && this->writer_ == t);
133
    this->writer_ = NULL;
134
  }
135
 
136
  // A blocker token uses these methods.
137
 
138
  // Add a blocker to the token.
139
  void
140
  add_blocker()
141
  {
142
    gold_assert(this->is_blocker_);
143
    ++this->blockers_;
144
    this->writer_ = NULL;
145
  }
146
 
147
  // Remove a blocker from the token.  Returns true if block count
148
  // drops to zero.
149
  bool
150
  remove_blocker()
151
  {
152
    gold_assert(this->is_blocker_ && this->blockers_ > 0);
153
    --this->blockers_;
154
    this->writer_ = NULL;
155
    return this->blockers_ == 0;
156
  }
157
 
158
  // Is the token currently blocked?
159
  bool
160
  is_blocked() const
161
  {
162
    gold_assert(this->is_blocker_);
163
    return this->blockers_ > 0;
164
  }
165
 
166
  // Both blocker and write lock tokens use these methods.
167
 
168
  // Add T to the list of tasks waiting for this token to be released.
169
  void
170
  add_waiting(Task* t)
171
  { this->waiting_.push_back(t); }
172
 
173
  // Add T to the front of the list of tasks waiting for this token to
174
  // be released.
175
  void
176
  add_waiting_front(Task* t)
177
  { this->waiting_.push_front(t); }
178
 
179
  // Remove the first Task waiting for this token to be released, and
180
  // return it.  Return NULL if no Tasks are waiting.
181
  Task*
182
  remove_first_waiting()
183
  { return this->waiting_.pop_front(); }
184
 
185
 private:
186
  // It makes no sense to copy these.
187
  Task_token(const Task_token&);
188
  Task_token& operator=(const Task_token&);
189
 
190
  // Whether this is a blocker token.
191
  bool is_blocker_;
192
  // The number of blockers.
193
  int blockers_;
194
  // The single writer.
195
  const Task* writer_;
196
  // The list of Tasks waiting for this token to be released.
197
  Task_list waiting_;
198
};
199
 
200
// In order to support tokens more reliably, we provide objects which
201
// handle them using RAII.
202
 
203
// RAII class to get a write lock on a token.  This requires
204
// specifying the task which is doing the lock.
205
 
206
class Task_write_token
207
{
208
 public:
209
  Task_write_token(Task_token* token, const Task* task)
210
    : token_(token), task_(task)
211
  { this->token_->add_writer(this->task_); }
212
 
213
  ~Task_write_token()
214
  { this->token_->remove_writer(this->task_); }
215
 
216
 private:
217
  Task_write_token(const Task_write_token&);
218
  Task_write_token& operator=(const Task_write_token&);
219
 
220
  Task_token* token_;
221
  const Task* task_;
222
};
223
 
224
// RAII class for a blocker.
225
 
226
class Task_block_token
227
{
228
 public:
229
  // The blocker count must be incremented when the task is created.
230
  // This object is created when the task is run, so we don't do
231
  // anything in the constructor.
232
  Task_block_token(Task_token* token)
233
    : token_(token)
234
  { gold_assert(this->token_->is_blocked()); }
235
 
236
  ~Task_block_token()
237
  { this->token_->remove_blocker(); }
238
 
239
 private:
240
  Task_block_token(const Task_block_token&);
241
  Task_block_token& operator=(const Task_block_token&);
242
 
243
  Task_token* token_;
244
};
245
 
246
// An object which implements an RAII lock for any object which
247
// supports lock and unlock methods.
248
 
249
template<typename Obj>
250
class Task_lock_obj
251
{
252
 public:
253
  Task_lock_obj(const Task* task, Obj* obj)
254
    : task_(task), obj_(obj)
255
  { this->obj_->lock(task); }
256
 
257
  ~Task_lock_obj()
258
  { this->obj_->unlock(this->task_); }
259
 
260
 private:
261
  Task_lock_obj(const Task_lock_obj&);
262
  Task_lock_obj& operator=(const Task_lock_obj&);
263
 
264
  const Task* task_;
265
  Obj* obj_;
266
};
267
 
268
// A class which holds the set of Task_tokens which must be locked for
269
// a Task.  No Task requires more than four Task_tokens, so we set
270
// that as a limit.
271
 
272
class Task_locker
273
{
274
 public:
275
  static const int max_task_count = 4;
276
 
277
  Task_locker()
278
    : count_(0)
279
  { }
280
 
281
  ~Task_locker()
282
  { }
283
 
284
  // Clear the locker.
285
  void
286
  clear()
287
  { this->count_ = 0; }
288
 
289
  // Add a token to the locker.
290
  void
291
  add(Task* t, Task_token* token)
292
  {
293
    gold_assert(this->count_ < max_task_count);
294
    this->tokens_[this->count_] = token;
295
    ++this->count_;
296
    // A blocker will have been incremented when the task is created.
297
    // A writer we need to lock now.
298
    if (!token->is_blocker())
299
      token->add_writer(t);
300
  }
301
 
302
  // Iterate over the tokens.
303
 
304
  typedef Task_token** iterator;
305
 
306
  iterator
307
  begin()
308
  { return &this->tokens_[0]; }
309
 
310
  iterator
311
  end()
312
  { return &this->tokens_[this->count_]; }
313
 
314
 private:
315
  Task_locker(const Task_locker&);
316
  Task_locker& operator=(const Task_locker&);
317
 
318
  // The number of tokens.
319
  int count_;
320
  // The tokens.
321
  Task_token* tokens_[max_task_count];
322
};
323
 
324
} // End namespace gold.
325
 
326
#endif // !defined(GOLD_TOKEN_H)

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.