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[/] [open8_urisc/] [trunk/] [gnu/] [binutils/] [gold/] [workqueue.h] - Blame information for rev 41

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// workqueue.h -- the work queue for gold   -*- C++ -*-
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// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
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// Written by Ian Lance Taylor <iant@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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// After processing the command line, everything the linker does is
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// driven from a work queue.  This permits us to parallelize the
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// linker where possible.
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#ifndef GOLD_WORKQUEUE_H
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#define GOLD_WORKQUEUE_H
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#include <string>
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#include "gold-threads.h"
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#include "token.h"
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namespace gold
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{
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class General_options;
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class Workqueue;
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// The superclass for tasks to be placed on the workqueue.  Each
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// specific task class will inherit from this one.
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class Task
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{
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 public:
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  Task()
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    : list_next_(NULL), name_(), should_run_soon_(false)
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  { }
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  virtual ~Task()
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  { }
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  // Check whether the Task can be run now.  This method is only
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  // called with the workqueue lock held.  If the Task can run, this
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  // returns NULL.  Otherwise it returns a pointer to a token which
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  // must be released before the Task can run.
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  virtual Task_token*
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  is_runnable() = 0;
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  // Lock all the resources required by the Task, and store the locks
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  // in a Task_locker.  This method does not need to do anything if no
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  // locks are required.  This method is only called with the
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  // workqueue lock held.
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  virtual void
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  locks(Task_locker*) = 0;
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  // Run the task.
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  virtual void
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  run(Workqueue*) = 0;
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  // Return whether this task should run soon.
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  bool
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  should_run_soon() const
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  { return this->should_run_soon_; }
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  // Note that this task should run soon.
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  void
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  set_should_run_soon()
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  { this->should_run_soon_ = true; }
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  // Get the next Task on the list of Tasks.  Called by Task_list.
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  Task*
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  list_next() const
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  { return this->list_next_; }
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  // Set the next Task on the list of Tasks.  Called by Task_list.
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  void
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  set_list_next(Task* t)
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  {
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    gold_assert(this->list_next_ == NULL);
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    this->list_next_ = t;
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  }
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  // Clear the next Task on the list of Tasks.  Called by Task_list.
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  void
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  clear_list_next()
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  { this->list_next_ = NULL; }
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  // Return the name of the Task.  This is only used for debugging
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  // purposes.
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  const std::string&
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  name()
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  {
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    if (this->name_.empty())
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      this->name_ = this->get_name();
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    return this->name_;
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  }
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 protected:
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  // Get the name of the task.  This must be implemented by the child
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  // class.
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  virtual std::string
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  get_name() const = 0;
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 private:
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  // Tasks may not be copied.
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  Task(const Task&);
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  Task& operator=(const Task&);
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  // If this Task is on a list, this is a pointer to the next Task on
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  // the list.  We use this simple list structure rather than building
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  // a container, in order to avoid memory allocation while holding
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  // the Workqueue lock.
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  Task* list_next_;
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  // Task name, for debugging purposes.
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  std::string name_;
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  // Whether this Task should be executed soon.  This is used for
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  // Tasks which can be run after some data is read.
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  bool should_run_soon_;
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};
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// An interface for Task_function.  This is a convenience class to run
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// a single function.
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class Task_function_runner
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{
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 public:
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  virtual ~Task_function_runner()
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  { }
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  virtual void
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  run(Workqueue*, const Task*) = 0;
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};
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// A simple task which waits for a blocker and then runs a function.
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class Task_function : public Task
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{
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 public:
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  // RUNNER and BLOCKER should be allocated using new, and will be
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  // deleted after the task runs.
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  Task_function(Task_function_runner* runner, Task_token* blocker,
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                const char* name)
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    : runner_(runner), blocker_(blocker), name_(name)
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  { gold_assert(blocker != NULL); }
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  ~Task_function()
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  {
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    delete this->runner_;
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    delete this->blocker_;
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  }
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  // The standard task methods.
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  // Wait until the task is unblocked.
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  Task_token*
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  is_runnable()
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  { return this->blocker_->is_blocked() ? this->blocker_ : NULL; }
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  // This type of task does not normally hold any locks.
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  virtual void
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  locks(Task_locker*)
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  { }
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  // Run the action.
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  void
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  run(Workqueue* workqueue)
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  { this->runner_->run(workqueue, this); }
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  // The debugging name.
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  std::string
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  get_name() const
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  { return this->name_; }
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 private:
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  Task_function(const Task_function&);
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  Task_function& operator=(const Task_function&);
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  Task_function_runner* runner_;
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  Task_token* blocker_;
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  const char* name_;
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};
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// The workqueue itself.
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class Workqueue_threader;
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class Workqueue
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{
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 public:
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  Workqueue(const General_options&);
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  ~Workqueue();
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  // Add a new task to the work queue.
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  void
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  queue(Task*);
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  // Add a new task to the work queue which should run soon.  If the
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  // task is ready, it will be run before any tasks added using
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  // queue().
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  void
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  queue_soon(Task*);
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  // Add a new task to the work queue which should run next if it is
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  // ready.
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  void
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  queue_next(Task*);
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  // Process all the tasks on the work queue.  This function runs
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  // until all tasks have completed.  The argument is the thread
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  // number, used only for debugging.
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  void
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  process(int);
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  // Set the desired thread count--the number of threads we want to
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  // have running.
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  void
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  set_thread_count(int);
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  // Add a new blocker to an existing Task_token. This must be done
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  // with the workqueue lock held.  This should not be done routinely,
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  // only in special circumstances.
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  void
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  add_blocker(Task_token*);
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 private:
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  // This class can not be copied.
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  Workqueue(const Workqueue&);
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  Workqueue& operator=(const Workqueue&);
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  // Add a task to a queue.
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  void
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  add_to_queue(Task_list* queue, Task* t, bool front);
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  // Find a runnable task, or wait for one.
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  Task*
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  find_runnable_or_wait(int thread_number);
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  // Find a runnable task.
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  Task*
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  find_runnable();
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  // Find a runnable task in a list.
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  Task*
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  find_runnable_in_list(Task_list*);
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  // Find an run a task.
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  bool
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  find_and_run_task(int);
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  // Release the locks for a Task.  Return the next Task to run.
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  Task*
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  release_locks(Task*, Task_locker*);
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  // Store T into *PRET, or queue it as appropriate.
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  bool
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  return_or_queue(Task* t, bool is_blocker, Task** pret);
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  // Return whether to cancel this thread.
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  bool
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  should_cancel_thread();
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  // Master Workqueue lock.  This controls access to the following
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  // member variables.
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  Lock lock_;
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  // List of tasks to execute soon.
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  Task_list first_tasks_;
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  // List of tasks to execute after the ones in first_tasks_.
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  Task_list tasks_;
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  // Number of tasks currently running.
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  int running_;
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  // Number of tasks waiting for a lock to release.
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  int waiting_;
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  // Condition variable associated with lock_.  This is signalled when
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  // there may be a new Task to execute.
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  Condvar condvar_;
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  // The threading implementation.  This is set at construction time
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  // and not changed thereafter.
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  Workqueue_threader* threader_;
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};
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} // End namespace gold.
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#endif // !defined(GOLD_WORKQUEUE_H)

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