// gold-threads.h -- thread support for gold -*- C++ -*-
+// Copyright (C) 2006-2020 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
namespace gold
{
-class Lock_impl;
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.
{
public:
Lock();
+
~Lock();
// Acquire the lock.
void
- acquire();
+ acquire()
+ { this->lock_->acquire(); }
// Release the lock.
void
- release();
+ release()
+ { this->lock_->release(); }
private:
// This class can not be copied.
Lock& lock_;
};
-class Condvar_impl;
+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.
// Wait for the condition variable to be signalled. This should
// only be called when the lock is held.
void
- wait();
+ wait()
+ { this->condvar_->wait(this->lock_.get_impl()); }
- // Signal the condition variable. This should only be called when
- // the lock is held.
+ // 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();
+ 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_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)
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