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// gold-threads.cc -- thread support for gold
// Copyright (C) 2006-2021 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_mutexattr_init failed: %s"), strerror(err));
#ifdef PTHREAD_MUTEX_ADAPTIVE_NP
err = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
if (err != 0)
gold_fatal(_("pthread_mutexattr_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.