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124 lines
3.3 KiB
C++
124 lines
3.3 KiB
C++
#pragma once
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#include <cstdint>
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#include <thread>
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#include <mutex>
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#include <condition_variable>
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#include <functional>
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#include <queue>
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#include <vector>
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#include <ext/singleton.h>
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/** Very simple thread pool similar to boost::threadpool.
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* Advantages:
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* - catches exceptions and rethrows on wait.
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*/
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template <typename Thread>
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class ThreadPoolImpl
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{
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public:
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using Job = std::function<void()>;
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/// Size is constant. Up to num_threads are created on demand and then run until shutdown.
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explicit ThreadPoolImpl(size_t num_threads);
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/// queue_size - maximum number of running plus scheduled jobs. It can be greater than num_threads. Zero means unlimited.
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ThreadPoolImpl(size_t num_threads, size_t queue_size);
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/// Add new job. Locks until number of active jobs is less than maximum or exception in one of threads was thrown.
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/// If an exception in some thread was thrown, method silently returns, and exception will be rethrown only on call to 'wait' function.
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/// Priority: greater is higher.
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void schedule(Job job, int priority = 0);
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/// Wait for all currently active jobs to be done.
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/// You may call schedule and wait many times in arbitary order.
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/// If any thread was throw an exception, first exception will be rethrown from this method,
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/// and exception will be cleared.
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void wait();
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/// Waits for all threads. Doesn't rethrow exceptions (use 'wait' method to rethrow exceptions).
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/// You should not destroy object while calling schedule or wait methods from another threads.
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~ThreadPoolImpl();
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size_t size() const { return num_threads; }
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/// Returns number of running and scheduled jobs.
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size_t active() const;
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private:
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mutable std::mutex mutex;
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std::condition_variable job_finished;
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std::condition_variable new_job_or_shutdown;
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const size_t num_threads;
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const size_t queue_size;
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size_t active_jobs = 0;
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bool shutdown = false;
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struct JobWithPriority
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{
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Job job;
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int priority;
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JobWithPriority(Job job, int priority)
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: job(job), priority(priority) {}
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bool operator< (const JobWithPriority & rhs) const
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{
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return priority < rhs.priority;
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}
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};
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std::priority_queue<JobWithPriority> jobs;
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std::vector<Thread> threads;
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std::exception_ptr first_exception;
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void worker();
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void finalize();
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};
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using FreeThreadPool = ThreadPoolImpl<std::thread>;
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class GlobalThreadPool : public FreeThreadPool, public ext::singleton<GlobalThreadPool>
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{
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public:
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GlobalThreadPool() : FreeThreadPool(10000) {} /// TODO: global blocking limit may lead to deadlocks.
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};
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class ThreadFromGlobalPool
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{
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public:
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ThreadFromGlobalPool(std::function<void()> func)
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{
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GlobalThreadPool::instance().schedule(func);
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}
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void join()
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{
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/// noop, the std::thread will continue to run inside global pool.
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}
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};
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using ThreadPool = ThreadPoolImpl<ThreadFromGlobalPool>;
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/// Allows to save first catched exception in jobs and postpone its rethrow.
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class ExceptionHandler
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{
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public:
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void setException(std::exception_ptr && exception);
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void throwIfException();
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private:
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std::exception_ptr first_exception;
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std::mutex mutex;
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};
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ThreadPool::Job createExceptionHandledJob(ThreadPool::Job job, ExceptionHandler & handler);
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