ceph/src/boost/libs/thread/include/boost/thread/executors/serial_executor.hpp

   1 // Copyright (C) 2013 Vicente J. Botet Escriba
   2 //
   3 //  Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5 //
   6 // 2013/11 Vicente J. Botet Escriba
   7 //    first implementation of a simple serial scheduler.
   8
   9 #ifndef BOOST_THREAD_SERIAL_EXECUTOR_HPP
  10 #define BOOST_THREAD_SERIAL_EXECUTOR_HPP
  11
  12 #include <boost/thread/detail/config.hpp>
  13 #include <boost/thread/detail/delete.hpp>
  14 #include <boost/thread/detail/move.hpp>
  15 #include <boost/thread/concurrent_queues/sync_queue.hpp>
  16 #include <boost/thread/executors/work.hpp>
  17 #include <boost/thread/executors/generic_executor_ref.hpp>
  18 #include <boost/thread/future.hpp>
  19 #include <boost/thread/scoped_thread.hpp>
  20
  21 #include <boost/config/abi_prefix.hpp>
  22
  23 namespace boost
  24 {
  25 namespace executors
  26 {
  27   class serial_executor
  28   {
  29   public:
  30     /// type-erasure to store the works to do
  31     typedef  executors::work work;
  32   private:
  33     typedef  scoped_thread<> thread_t;
  34
  35     /// the thread safe work queue
  36     concurrent::sync_queue<work > work_queue;
  37     generic_executor_ref ex;
  38     thread_t thr;
  39
  40     struct try_executing_one_task {
  41       work& task;
  42       boost::promise<void> &p;
  43       try_executing_one_task(work& task, boost::promise<void> &p)
  44       : task(task), p(p) {}
  45       void operator()() {
  46         try {
  47           task();
  48           p.set_value();
  49         } catch (...)
  50         {
  51           p.set_exception(current_exception());
  52         }
  53       }
  54     };
  55   public:
  56     /**
  57      * \par Returns
  58      * The underlying executor wrapped on a generic executor reference.
  59      */
  60     generic_executor_ref& underlying_executor() BOOST_NOEXCEPT { return ex; }
  61
  62     /**
  63      * Effects: try to execute one task.
  64      * Returns: whether a task has been executed.
  65      * Throws: whatever the current task constructor throws or the task() throws.
  66      */
  67     bool try_executing_one()
  68     {
  69       work task;
  70       try
  71       {
  72         if (work_queue.try_pull(task) == queue_op_status::success)
  73         {
  74           boost::promise<void> p;
  75           try_executing_one_task tmp(task,p);
  76           ex.submit(tmp);
  77           p.get_future().wait();
  78           return true;
  79         }
  80         return false;
  81       }
  82       catch (...)
  83       {
  84         std::terminate();
  85         //return false;
  86       }
  87     }
  88   private:
  89     /**
  90      * Effects: schedule one task or yields
  91      * Throws: whatever the current task constructor throws or the task() throws.
  92      */
  93     void schedule_one_or_yield()
  94     {
  95         if ( ! try_executing_one())
  96         {
  97           this_thread::yield();
  98         }
  99     }
 100
 101     /**
 102      * The main loop of the worker thread
 103      */
 104     void worker_thread()
 105     {
 106       while (!closed())
 107       {
 108         schedule_one_or_yield();
 109       }
 110       while (try_executing_one())
 111       {
 112       }
 113     }
 114
 115   public:
 116     /// serial_executor is not copyable.
 117     BOOST_THREAD_NO_COPYABLE(serial_executor)
 118
 119     /**
 120      * \b Effects: creates a thread pool that runs closures using one of its closure-executing methods.
 121      *
 122      * \b Throws: Whatever exception is thrown while initializing the needed resources.
 123      */
 124     template <class Executor>
 125     serial_executor(Executor& ex)
 126     : ex(ex), thr(&serial_executor::worker_thread, this)
 127     {
 128     }
 129     /**
 130      * \b Effects: Destroys the thread pool.
 131      *
 132      * \b Synchronization: The completion of all the closures happen before the completion of the \c serial_executor destructor.
 133      */
 134     ~serial_executor()
 135     {
 136       // signal to the worker thread that there will be no more submissions.
 137       close();
 138     }
 139
 140     /**
 141      * \b Effects: close the \c serial_executor for submissions.
 142      * The loop will work until there is no more closures to run.
 143      */
 144     void close()
 145     {
 146       work_queue.close();
 147     }
 148
 149     /**
 150      * \b Returns: whether the pool is closed for submissions.
 151      */
 152     bool closed()
 153     {
 154       return work_queue.closed();
 155     }
 156
 157     /**
 158      * \b Requires: \c Closure is a model of \c Callable(void()) and a model of \c CopyConstructible/MoveConstructible.
 159      *
 160      * \b Effects: The specified \c closure will be scheduled for execution at some point in the future.
 161      * If invoked closure throws an exception the \c serial_executor will call \c std::terminate, as is the case with threads.
 162      *
 163      * \b Synchronization: completion of \c closure on a particular thread happens before destruction of thread's thread local variables.
 164      *
 165      * \b Throws: \c sync_queue_is_closed if the thread pool is closed.
 166      * Whatever exception that can be throw while storing the closure.
 167      */
 168     void submit(BOOST_THREAD_RV_REF(work) closure)
 169     {
 170       work_queue.push(boost::move(closure));
 171     }
 172
 173 #if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
 174     template <typename Closure>
 175     void submit(Closure & closure)
 176     {
 177       submit(work(closure));
 178     }
 179 #endif
 180     void submit(void (*closure)())
 181     {
 182       submit(work(closure));
 183     }
 184
 185     template <typename Closure>
 186     void submit(BOOST_THREAD_FWD_REF(Closure) closure)
 187     {
 188       work w((boost::forward<Closure>(closure)));
 189       submit(boost::move(w));
 190     }
 191
 192     /**
 193      * \b Requires: This must be called from an scheduled task.
 194      *
 195      * \b Effects: reschedule functions until pred()
 196      */
 197     template <typename Pred>
 198     bool reschedule_until(Pred const& pred)
 199     {
 200       do {
 201         if ( ! try_executing_one())
 202         {
 203           return false;
 204         }
 205       } while (! pred());
 206       return true;
 207     }
 208
 209   };
 210 }
 211 using executors::serial_executor;
 212 }
 213
 214 #include <boost/config/abi_suffix.hpp>
 215
 216 #endif