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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
/**
* @class document::Runnable
* @ingroup util
*
* @brief Implementation of FastOS_Runnable that implements threadsafe stop.
*
* FastOS_Runnable can easily be used unsafe. If you use the thread pointer for
* anything after your runnable had returned from Run(), it could affect another
* runnable now using that thread.
*
* Using this class should be foolproof to avoid synchronization issues during
* thread starting and stopping :)
*
* @author H�kon Humberset
* @date 2005-09-19
*/
#pragma once
#include <vespa/fastos/thread.h>
#include <atomic>
namespace document {
class Runnable : private FastOS_Runnable {
public:
enum State { NOT_RUNNING, STARTING, RUNNING, STOPPING };
private:
mutable std::mutex _stateLock;
mutable std::condition_variable _stateCond;
std::atomic<State> _state;
void Run(FastOS_ThreadInterface*, void*) override;
void set_state(State new_state) noexcept; // _stateLock must be held
public:
/**
* Create a runnable.
* @param pool If set, runnable will be started in constructor.
*/
Runnable();
~Runnable() override;
/**
* Start this runnable.
* @param pool The threadpool from which a thread is acquired.
* @return True if thread was started, false if thread was already running.
*/
bool start(FastOS_ThreadPool& pool);
/**
* Stop this runnable.
* @return True if thread was stopped, false if thread was not running.
*/
bool stop();
/**
* Called in stop(). Implement, to for instance notify any monitors that
* can be waiting.
*/
virtual bool onStop();
/**
* Wait for this thread to finish, if it is in the process of stopping.
* @return True if thread finished (or not running), false if thread is
* running normally and no stop is scheduled.
*/
bool join() const;
/**
* Implement this to make the runnable actually do something.
*/
virtual void run() = 0;
/**
* Get the current state of this runnable.
* Thread safe (but relaxed) read; may be stale if done outside _stateLock.
*/
[[nodiscard]] State getState() const noexcept {
return _state.load(std::memory_order_relaxed);
}
/** Check if system is in the process of stopping. */
[[nodiscard]] bool stopping() const noexcept;
/**
* Checks if runnable is running or not. (Started is considered running)
*/
[[nodiscard]] bool running() const noexcept;
FastOS_ThreadId native_thread_id() const noexcept;
};
}
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