gold/gold-threads.cc

   1 // gold-threads.cc -- thread support for gold
   2
   3 // Copyright (C) 2006-2020 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 #include "gold.h"
  24
  25 #include <cstring>
  26
  27 #ifdef ENABLE_THREADS
  28 #include <pthread.h>
  29 #endif
  30
  31 #include "options.h"
  32 #include "parameters.h"
  33 #include "gold-threads.h"
  34
  35 namespace gold
  36 {
  37
  38 class Condvar_impl_nothreads;
  39
  40 // The non-threaded version of Lock_impl.
  41
  42 class Lock_impl_nothreads : public Lock_impl
  43 {
  44  public:
  45   Lock_impl_nothreads()
  46     : acquired_(false)
  47   { }
  48
  49   ~Lock_impl_nothreads()
  50   { gold_assert(!this->acquired_); }
  51
  52   void
  53   acquire()
  54   {
  55     gold_assert(!this->acquired_);
  56     this->acquired_ = true;
  57   }
  58
  59   void
  60   release()
  61   {
  62     gold_assert(this->acquired_);
  63     this->acquired_ = false;
  64   }
  65
  66  private:
  67   friend class Condvar_impl_nothreads;
  68
  69   bool acquired_;
  70 };
  71
  72 #ifdef ENABLE_THREADS
  73
  74 class Condvar_impl_threads;
  75
  76 // The threaded version of Lock_impl.
  77
  78 class Lock_impl_threads : public Lock_impl
  79 {
  80  public:
  81   Lock_impl_threads();
  82   ~Lock_impl_threads();
  83
  84   void acquire();
  85
  86   void release();
  87
  88 private:
  89   // This class can not be copied.
  90   Lock_impl_threads(const Lock_impl_threads&);
  91   Lock_impl_threads& operator=(const Lock_impl_threads&);
  92
  93   friend class Condvar_impl_threads;
  94
  95   pthread_mutex_t mutex_;
  96 };
  97
  98 Lock_impl_threads::Lock_impl_threads()
  99 {
 100   pthread_mutexattr_t attr;
 101   int err = pthread_mutexattr_init(&attr);
 102   if (err != 0)
 103     gold_fatal(_("pthead_mutexattr_init failed: %s"), strerror(err));
 104 #ifdef PTHREAD_MUTEX_ADAPTIVE_NP
 105   err = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
 106   if (err != 0)
 107     gold_fatal(_("pthread_mutexattr_settype failed: %s"), strerror(err));
 108 #endif
 109
 110   err = pthread_mutex_init(&this->mutex_, &attr);
 111   if (err != 0)
 112     gold_fatal(_("pthread_mutex_init failed: %s"), strerror(err));
 113
 114   err = pthread_mutexattr_destroy(&attr);
 115   if (err != 0)
 116     gold_fatal(_("pthread_mutexattr_destroy failed: %s"), strerror(err));
 117 }
 118
 119 Lock_impl_threads::~Lock_impl_threads()
 120 {
 121   int err = pthread_mutex_destroy(&this->mutex_);
 122   if (err != 0)
 123     gold_fatal(_("pthread_mutex_destroy failed: %s"), strerror(err));
 124 }
 125
 126 void
 127 Lock_impl_threads::acquire()
 128 {
 129   int err = pthread_mutex_lock(&this->mutex_);
 130   if (err != 0)
 131     gold_fatal(_("pthread_mutex_lock failed: %s"), strerror(err));
 132 }
 133
 134 void
 135 Lock_impl_threads::release()
 136 {
 137   int err = pthread_mutex_unlock(&this->mutex_);
 138   if (err != 0)
 139     gold_fatal(_("pthread_mutex_unlock failed: %s"), strerror(err));
 140 }
 141
 142 #endif // defined(ENABLE_THREADS)
 143
 144 // Class Lock.
 145
 146 Lock::Lock()
 147 {
 148   if (!parameters->options().threads())
 149     this->lock_ = new Lock_impl_nothreads;
 150   else
 151     {
 152 #ifdef ENABLE_THREADS
 153       this->lock_ = new Lock_impl_threads;
 154 #else
 155       gold_unreachable();
 156 #endif
 157     }
 158 }
 159
 160 Lock::~Lock()
 161 {
 162   delete this->lock_;
 163 }
 164
 165 // The non-threaded version of Condvar_impl.
 166
 167 class Condvar_impl_nothreads : public Condvar_impl
 168 {
 169  public:
 170   Condvar_impl_nothreads()
 171   { }
 172
 173   ~Condvar_impl_nothreads()
 174   { }
 175
 176   void
 177   wait(Lock_impl* li)
 178   { gold_assert(static_cast<Lock_impl_nothreads*>(li)->acquired_); }
 179
 180   void
 181   signal()
 182   { }
 183
 184   void
 185   broadcast()
 186   { }
 187 };
 188
 189 #ifdef ENABLE_THREADS
 190
 191 // The threaded version of Condvar_impl.
 192
 193 class Condvar_impl_threads : public Condvar_impl
 194 {
 195  public:
 196   Condvar_impl_threads();
 197   ~Condvar_impl_threads();
 198
 199   void
 200   wait(Lock_impl*);
 201
 202   void
 203   signal();
 204
 205   void
 206   broadcast();
 207
 208  private:
 209   // This class can not be copied.
 210   Condvar_impl_threads(const Condvar_impl_threads&);
 211   Condvar_impl_threads& operator=(const Condvar_impl_threads&);
 212
 213   pthread_cond_t cond_;
 214 };
 215
 216 Condvar_impl_threads::Condvar_impl_threads()
 217 {
 218   int err = pthread_cond_init(&this->cond_, NULL);
 219   if (err != 0)
 220     gold_fatal(_("pthread_cond_init failed: %s"), strerror(err));
 221 }
 222
 223 Condvar_impl_threads::~Condvar_impl_threads()
 224 {
 225   int err = pthread_cond_destroy(&this->cond_);
 226   if (err != 0)
 227     gold_fatal(_("pthread_cond_destroy failed: %s"), strerror(err));
 228 }
 229
 230 void
 231 Condvar_impl_threads::wait(Lock_impl* li)
 232 {
 233   Lock_impl_threads* lit = static_cast<Lock_impl_threads*>(li);
 234   int err = pthread_cond_wait(&this->cond_, &lit->mutex_);
 235   if (err != 0)
 236     gold_fatal(_("pthread_cond_wait failed: %s"), strerror(err));
 237 }
 238
 239 void
 240 Condvar_impl_threads::signal()
 241 {
 242   int err = pthread_cond_signal(&this->cond_);
 243   if (err != 0)
 244     gold_fatal(_("pthread_cond_signal failed: %s"), strerror(err));
 245 }
 246
 247 void
 248 Condvar_impl_threads::broadcast()
 249 {
 250   int err = pthread_cond_broadcast(&this->cond_);
 251   if (err != 0)
 252     gold_fatal(_("pthread_cond_broadcast failed: %s"), strerror(err));
 253 }
 254
 255 #endif // defined(ENABLE_THREADS)
 256
 257 // Methods for Condvar class.
 258
 259 Condvar::Condvar(Lock& lock)
 260   : lock_(lock)
 261 {
 262   if (!parameters->options().threads())
 263     this->condvar_ = new Condvar_impl_nothreads;
 264   else
 265     {
 266 #ifdef ENABLE_THREADS
 267       this->condvar_ = new Condvar_impl_threads;
 268 #else
 269       gold_unreachable();
 270 #endif
 271     }
 272 }
 273
 274 Condvar::~Condvar()
 275 {
 276   delete this->condvar_;
 277 }
 278
 279 #ifdef ENABLE_THREADS
 280
 281 // Class Once_initialize.  This exists to hold a pthread_once_t
 282 // structure for Once.
 283
 284 class Once_initialize
 285 {
 286  public:
 287   Once_initialize()
 288     : once_(PTHREAD_ONCE_INIT)
 289   { }
 290
 291   // Return a pointer to the pthread_once_t variable.
 292   pthread_once_t*
 293   once_control()
 294   { return &this->once_; }
 295
 296  private:
 297   pthread_once_t once_;
 298 };
 299
 300 #endif // defined(ENABLE_THREADS)
 301
 302 #ifdef ENABLE_THREADS
 303
 304 // A single lock which controls access to once_pointer.  This is used
 305 // because we can't pass parameters to functions passed to
 306 // pthread_once.
 307
 308 static pthread_mutex_t once_pointer_control = PTHREAD_MUTEX_INITIALIZER;
 309
 310 // A pointer to Once structure we want to run.  Access to this is
 311 // controlled by once_pointer_control.
 312
 313 static Once* once_pointer;
 314
 315 // The argument to pass to the Once structure.  Access to this is
 316 // controlled by once_pointer_control.
 317
 318 static void* once_arg;
 319
 320 // A routine passed to pthread_once which runs the Once pointer.
 321
 322 extern "C"
 323 {
 324
 325 static void
 326 c_run_once(void)
 327 {
 328   once_pointer->internal_run(once_arg);
 329 }
 330
 331 }
 332
 333 #endif // defined(ENABLE_THREADS)
 334
 335 // Class Once.
 336
 337 Once::Once()
 338   : was_run_(false)
 339 #if defined(ENABLE_THREADS) && defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4)
 340     , was_run_lock_(0)
 341 #endif
 342 {
 343 #ifndef ENABLE_THREADS
 344   this->once_ = NULL;
 345 #else
 346   this->once_ = new Once_initialize();
 347 #endif
 348 }
 349
 350 // Run the function once.
 351
 352 void
 353 Once::run_once(void* arg)
 354 {
 355 #ifndef ENABLE_THREADS
 356
 357   // If there is no threads support, we don't need to use pthread_once.
 358   if (!this->was_run_)
 359     this->internal_run(arg);
 360
 361 #else // defined(ENABLE_THREADS)
 362
 363   if (parameters->options_valid() && !parameters->options().threads())
 364     {
 365       // If we are not using threads, we don't need to lock.
 366       if (!this->was_run_)
 367         this->internal_run(arg);
 368       return;
 369     }
 370
 371   // If we have the sync builtins, use them to skip the lock if the
 372   // value has already been initialized.
 373 #ifdef __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
 374   while (true)
 375     {
 376       if (__sync_bool_compare_and_swap(&this->was_run_lock_, 0, 1))
 377         break;
 378     }
 379   bool was_run = this->was_run_;
 380   while (true)
 381     {
 382       if (__sync_bool_compare_and_swap(&this->was_run_lock_, 1, 0))
 383         break;
 384     }
 385   if (was_run)
 386     return;
 387 #endif
 388
 389   // Since we can't pass parameters to routines called by
 390   // pthread_once, we use a static variable: once_pointer.  This in
 391   // turns means that we need to use a mutex to control access to
 392   // once_pointer.
 393
 394   int err = pthread_mutex_lock(&once_pointer_control);
 395   if (err != 0)
 396     gold_fatal(_("pthread_mutex_lock failed: %s"), strerror(err));
 397
 398   once_pointer = this;
 399   once_arg = arg;
 400
 401   err = pthread_once(this->once_->once_control(), c_run_once);
 402   if (err != 0)
 403     gold_fatal(_("pthread_once failed: %s"), strerror(err));
 404
 405   once_pointer = NULL;
 406   once_arg = NULL;
 407
 408   err = pthread_mutex_unlock(&once_pointer_control);
 409   if (err != 0)
 410     gold_fatal(_("pthread_mutex_unlock failed: %s"), strerror(err));
 411
 412 #endif // defined(ENABLE_THREADS)
 413 }
 414
 415 // Actually run the function in the child class.  This function will
 416 // be run only once.
 417
 418 void
 419 Once::internal_run(void* arg)
 420 {
 421   this->do_run_once(arg);
 422   this->was_run_ = true;
 423 }
 424
 425 // Class Initialize_lock.
 426
 427 // Initialize the lock.
 428
 429 bool
 430 Initialize_lock::initialize()
 431 {
 432   // We can't initialize the lock until we have read the options.
 433   if (!parameters->options_valid())
 434     return false;
 435   else
 436     {
 437       this->run_once(NULL);
 438       return true;
 439     }
 440 }
 441
 442 // Initialize the lock exactly once.
 443
 444 void
 445 Initialize_lock::do_run_once(void*)
 446 {
 447   *this->pplock_ = new Lock();
 448 }
 449
 450 } // End namespace gold.