aboutsummaryrefslogtreecommitdiff
path: root/gold/gold-threads.cc
blob: ebd9c1f2c4365d35184d69d359506daa1b80c689 (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
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
// gold-threads.cc -- thread support for gold

// Copyright (C) 2006-2014 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.

#include "gold.h"

#include <cstring>

#ifdef ENABLE_THREADS
#include <pthread.h>
#endif

#include "options.h"
#include "parameters.h"
#include "gold-threads.h"

namespace gold
{

class Condvar_impl_nothreads;

// The non-threaded version of Lock_impl.

class Lock_impl_nothreads : public Lock_impl
{
 public:
  Lock_impl_nothreads()
    : acquired_(false)
  { }

  ~Lock_impl_nothreads()
  { gold_assert(!this->acquired_); }

  void
  acquire()
  {
    gold_assert(!this->acquired_);
    this->acquired_ = true;
  }

  void
  release()
  {
    gold_assert(this->acquired_);
    this->acquired_ = false;
  }

 private:
  friend class Condvar_impl_nothreads;

  bool acquired_;
};

#ifdef ENABLE_THREADS

class Condvar_impl_threads;

// The threaded version of Lock_impl.

class Lock_impl_threads : public Lock_impl
{
 public:
  Lock_impl_threads();
  ~Lock_impl_threads();

  void acquire();

  void release();

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

  friend class Condvar_impl_threads;

  pthread_mutex_t mutex_;
};

Lock_impl_threads::Lock_impl_threads()
{
  pthread_mutexattr_t attr;
  int err = pthread_mutexattr_init(&attr);
  if (err != 0)
    gold_fatal(_("pthead_mutextattr_init failed: %s"), strerror(err));
#ifdef PTHREAD_MUTEX_ADAPTIVE_NP
  err = pthread_mutextattr_settype(&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
  if (err != 0)
    gold_fatal(_("pthread_mutextattr_settype failed: %s"), strerror(err));
#endif

  err = pthread_mutex_init(&this->mutex_, &attr);
  if (err != 0)
    gold_fatal(_("pthread_mutex_init failed: %s"), strerror(err));

  err = pthread_mutexattr_destroy(&attr);
  if (err != 0)
    gold_fatal(_("pthread_mutexattr_destroy failed: %s"), strerror(err));
}

Lock_impl_threads::~Lock_impl_threads()
{
  int err = pthread_mutex_destroy(&this->mutex_);
  if (err != 0)
    gold_fatal(_("pthread_mutex_destroy failed: %s"), strerror(err));
}

void
Lock_impl_threads::acquire()
{
  int err = pthread_mutex_lock(&this->mutex_);
  if (err != 0)
    gold_fatal(_("pthread_mutex_lock failed: %s"), strerror(err));
}

void
Lock_impl_threads::release()
{
  int err = pthread_mutex_unlock(&this->mutex_);
  if (err != 0)
    gold_fatal(_("pthread_mutex_unlock failed: %s"), strerror(err));
}

#endif // defined(ENABLE_THREADS)

// Class Lock.

Lock::Lock()
{
  if (!parameters->options().threads())
    this->lock_ = new Lock_impl_nothreads;
  else
    {
#ifdef ENABLE_THREADS
      this->lock_ = new Lock_impl_threads;
#else
      gold_unreachable();
#endif
    }
}

Lock::~Lock()
{
  delete this->lock_;
}

// The non-threaded version of Condvar_impl.

class Condvar_impl_nothreads : public Condvar_impl
{
 public:
  Condvar_impl_nothreads()
  { }

  ~Condvar_impl_nothreads()
  { }

  void
  wait(Lock_impl* li)
  { gold_assert(static_cast<Lock_impl_nothreads*>(li)->acquired_); }

  void
  signal()
  { }

  void
  broadcast()
  { }
};

#ifdef ENABLE_THREADS

// The threaded version of Condvar_impl.

class Condvar_impl_threads : public Condvar_impl
{
 public:
  Condvar_impl_threads();
  ~Condvar_impl_threads();

  void
  wait(Lock_impl*);

  void
  signal();

  void
  broadcast();

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

  pthread_cond_t cond_;
};

Condvar_impl_threads::Condvar_impl_threads()
{
  int err = pthread_cond_init(&this->cond_, NULL);
  if (err != 0)
    gold_fatal(_("pthread_cond_init failed: %s"), strerror(err));
}

Condvar_impl_threads::~Condvar_impl_threads()
{
  int err = pthread_cond_destroy(&this->cond_);
  if (err != 0)
    gold_fatal(_("pthread_cond_destroy failed: %s"), strerror(err));
}

void
Condvar_impl_threads::wait(Lock_impl* li)
{
  Lock_impl_threads* lit = static_cast<Lock_impl_threads*>(li);
  int err = pthread_cond_wait(&this->cond_, &lit->mutex_);
  if (err != 0)
    gold_fatal(_("pthread_cond_wait failed: %s"), strerror(err));
}

void
Condvar_impl_threads::signal()
{
  int err = pthread_cond_signal(&this->cond_);
  if (err != 0)
    gold_fatal(_("pthread_cond_signal failed: %s"), strerror(err));
}

void
Condvar_impl_threads::broadcast()
{
  int err = pthread_cond_broadcast(&this->cond_);
  if (err != 0)
    gold_fatal(_("pthread_cond_broadcast failed: %s"), strerror(err));
}

#endif // defined(ENABLE_THREADS)

// Methods for Condvar class.

Condvar::Condvar(Lock& lock)
  : lock_(lock)
{
  if (!parameters->options().threads())
    this->condvar_ = new Condvar_impl_nothreads;
  else
    {
#ifdef ENABLE_THREADS
      this->condvar_ = new Condvar_impl_threads;
#else
      gold_unreachable();
#endif
    }
}

Condvar::~Condvar()
{
  delete this->condvar_;
}

#ifdef ENABLE_THREADS

// Class Once_initialize.  This exists to hold a pthread_once_t
// structure for Once.

class Once_initialize
{
 public:
  Once_initialize()
    : once_(PTHREAD_ONCE_INIT)
  { }

  // Return a pointer to the pthread_once_t variable.
  pthread_once_t*
  once_control()
  { return &this->once_; }

 private:
  pthread_once_t once_;
};

#endif // defined(ENABLE_THREADS)

#ifdef ENABLE_THREADS

// A single lock which controls access to once_pointer.  This is used
// because we can't pass parameters to functions passed to
// pthread_once.

static pthread_mutex_t once_pointer_control = PTHREAD_MUTEX_INITIALIZER;

// A pointer to Once structure we want to run.  Access to this is
// controlled by once_pointer_control.

static Once* once_pointer;

// The argument to pass to the Once structure.  Access to this is
// controlled by once_pointer_control.

static void* once_arg;

// A routine passed to pthread_once which runs the Once pointer.

extern "C"
{

static void
c_run_once(void)
{
  once_pointer->internal_run(once_arg);
}

}

#endif // defined(ENABLE_THREADS)

// Class Once.

Once::Once()
  : was_run_(false)
#if defined(ENABLE_THREADS) && defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
    , was_run_lock_(0)
#endif
{
#ifndef ENABLE_THREADS
  this->once_ = NULL;
#else
  this->once_ = new Once_initialize();
#endif
}

// Run the function once.

void
Once::run_once(void* arg)
{
#ifndef ENABLE_THREADS

  // If there is no threads support, we don't need to use pthread_once.
  if (!this->was_run_)
    this->internal_run(arg);

#else // defined(ENABLE_THREADS)

  if (parameters->options_valid() && !parameters->options().threads())
    {
      // If we are not using threads, we don't need to lock.
      if (!this->was_run_)
	this->internal_run(arg);
      return;
    }

  // If we have the sync builtins, use them to skip the lock if the
  // value has already been initialized.
#ifdef __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
  while (true)
    {
      if (__sync_bool_compare_and_swap(&this->was_run_lock_, 0, 1))
	break;
    }
  bool was_run = this->was_run_;
  while (true)
    {
      if (__sync_bool_compare_and_swap(&this->was_run_lock_, 1, 0))
	break;
    }
  if (was_run)
    return;
#endif

  // Since we can't pass parameters to routines called by
  // pthread_once, we use a static variable: once_pointer.  This in
  // turns means that we need to use a mutex to control access to
  // once_pointer.

  int err = pthread_mutex_lock(&once_pointer_control);
  if (err != 0)
    gold_fatal(_("pthread_mutex_lock failed: %s"), strerror(err));

  once_pointer = this;
  once_arg = arg;

  err = pthread_once(this->once_->once_control(), c_run_once);
  if (err != 0)
    gold_fatal(_("pthread_once failed: %s"), strerror(err));

  once_pointer = NULL;
  once_arg = NULL;

  err = pthread_mutex_unlock(&once_pointer_control);
  if (err != 0)
    gold_fatal(_("pthread_mutex_unlock failed: %s"), strerror(err));

#endif // defined(ENABLE_THREADS)
}

// Actually run the function in the child class.  This function will
// be run only once.

void
Once::internal_run(void* arg)
{
  this->do_run_once(arg);
  this->was_run_ = true;
}

// Class Initialize_lock.

// Initialize the lock.

bool
Initialize_lock::initialize()
{
  // We can't initialize the lock until we have read the options.
  if (!parameters->options_valid())
    return false;
  else
    {
      this->run_once(NULL);
      return true;
    }
}

// Initialize the lock exactly once.

void
Initialize_lock::do_run_once(void*)
{
  *this->pplock_ = new Lock();
}

} // End namespace gold.