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296 lines
7.4 KiB
C++
296 lines
7.4 KiB
C++
// workqueue.h -- the work queue for gold -*- C++ -*-
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// Copyright (C) 2006-2014 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(int thread_number);
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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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