Use a threadpool

Instead of constantly creating and destroying threads

15 files changed, 302 insertions, 963 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 55b8ad3e6..19d90253b 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -37,8 +37,7 @@ set(common_sources
   i18n.cpp
   password.cpp
   perf_timer.cpp
-  task_region.cpp
-  thread_group.cpp
+  threadpool.cpp
   updates.cpp)
 
 if (STACK_TRACE)
@@ -66,8 +65,7 @@ set(common_private_headers
   password.h
   perf_timer.h
   stack_trace.h
-  task_region.h
-  thread_group.h
+  threadpool.h
   updates.h)
 
 monero_private_headers(common
diff --git a/src/common/common_fwd.h b/src/common/common_fwd.h
index 5d67251b1..f33e185b5 100644
--- a/src/common/common_fwd.h
+++ b/src/common/common_fwd.h
@@ -36,6 +36,5 @@ namespace tools
   struct login;
   class password_container;
   class t_http_connection;
-  class task_region;
-  class thread_group;
+  class threadpool;
 }
diff --git a/src/common/task_region.cpp b/src/common/task_region.cpp
deleted file mode 100644
index 9b4620c6e..000000000
--- a/src/common/task_region.cpp
+++ /dev/null
@@ -1,94 +0,0 @@
-// Copyright (c) 2014-2017, The Monero Project
-// 
-// All rights reserved.
-// 
-// Redistribution and use in source and binary forms, with or without modification, are
-// permitted provided that the following conditions are met:
-// 
-// 1. Redistributions of source code must retain the above copyright notice, this list of
-//    conditions and the following disclaimer.
-// 
-// 2. Redistributions in binary form must reproduce the above copyright notice, this list
-//    of conditions and the following disclaimer in the documentation and/or other
-//    materials provided with the distribution.
-// 
-// 3. Neither the name of the copyright holder nor the names of its contributors may be
-//    used to endorse or promote products derived from this software without specific
-//    prior written permission.
-// 
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
-// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
-// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
-// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#include "common/task_region.h"
-
-#include <boost/thread/locks.hpp>
-#include <cassert>
-
-/* `mark_completed` and `wait` can throw in the lock call, but its difficult to
-recover from either. An exception in `wait` means the post condition of joining
-all threads cannot be achieved, and an exception in `mark_completed` means
-certain deadlock. `noexcept` qualifier will force a call to `std::terminate` if
-locking throws an exception, which should only happen if a recursive lock
-attempt is made (which is not possible since no external function is called
-while holding the lock). */
-
-namespace tools
-{
-void task_region_handle::state::mark_completed(id task_id) noexcept {
-  assert(task_id != 0 && (task_id & (task_id - 1)) == 0); // power of 2 check
-  if (pending.fetch_and(~task_id) == task_id) {
-    // synchronize with wait call, but do not need to hold
-    boost::unique_lock<boost::mutex>{sync_on_complete};
-    all_complete.notify_all();
-  }
-}
-
-void task_region_handle::state::abort() noexcept {
-  state* current = this;
-  while (current) {
-    current->ready = 0;
-    current = current->next.get();
-  }
-}
-
-void task_region_handle::state::wait() noexcept {
-  state* current = this;
-  while (current) {
-    {
-      boost::unique_lock<boost::mutex> lock{current->sync_on_complete};
-      current->all_complete.wait(lock, [current] { return current->pending == 0; });
-    }
-    current = current->next.get();
-  }
-}
-
-void task_region_handle::state::wait(thread_group& threads) noexcept {
-  state* current = this;
-  while (current) {
-    while (current->pending != 0) {
-      if (!threads.try_run_one()) {
-        current->wait();
-        return;
-      }
-    }
-    current = current->next.get();
-  }
-}
-
-void task_region_handle::create_state() {
-  st = std::make_shared<state>(std::move(st));
-  next_id = 1;
-}
-
-void task_region_handle::do_wait() noexcept {
-  assert(st);
-  const std::shared_ptr<state> temp = std::move(st);
-  temp->wait(threads);
-}
-}
diff --git a/src/common/task_region.h b/src/common/task_region.h
deleted file mode 100644
index 30972cce3..000000000
--- a/src/common/task_region.h
+++ /dev/null
@@ -1,223 +0,0 @@
-// Copyright (c) 2014-2017, The Monero Project
-// 
-// All rights reserved.
-// 
-// Redistribution and use in source and binary forms, with or without modification, are
-// permitted provided that the following conditions are met:
-// 
-// 1. Redistributions of source code must retain the above copyright notice, this list of
-//    conditions and the following disclaimer.
-// 
-// 2. Redistributions in binary form must reproduce the above copyright notice, this list
-//    of conditions and the following disclaimer in the documentation and/or other
-//    materials provided with the distribution.
-// 
-// 3. Neither the name of the copyright holder nor the names of its contributors may be
-//    used to endorse or promote products derived from this software without specific
-//    prior written permission.
-// 
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
-// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
-// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
-// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#pragma once
-
-#include <atomic>
-#include <boost/thread/condition_variable.hpp>
-#include <boost/thread/mutex.hpp>
-#include <memory>
-#include <type_traits>
-#include <utility>
-
-#include "common/thread_group.h"
-
-namespace tools
-{
-
-/*! A model of the fork-join concept. `run(...)` "forks" (i.e. spawns new
-tasks), and `~task_region_handle()` or `wait()` "joins" the spawned tasks.
-`wait` will block until all tasks have completed, while `~task_region_handle()`
-blocks until all tasks have completed or aborted.
-
-Do _NOT_ give this object to separate thread of execution (which includes
-`task_region_handle::run(...)`) because joining on a different thread is
-undesireable (potential deadlock). 
-
-This class cannot be constructed directly, use the function
-`task_region(...)` instead.
-*/
-class task_region_handle
-{
-  struct state
-  {
-    using id = unsigned;
-
-    explicit state(std::shared_ptr<state> next_src) noexcept
-      : next(std::move(next_src))
-      , ready(0)
-      , pending(0)
-      , sync_on_complete()
-      , all_complete() {
-    }
-      
-    state(const state&) = default;
-    state(state&&) = default;
-    ~state() = default;
-    state& operator=(const state&) = default;
-    state& operator=(state&&) = default;
-
-    void track_id(id task_id) noexcept {
-      pending |= task_id;
-      ready |= task_id;
-    }
-
-    //! \return True only once whether a given id can execute
-    bool can_run(id task_id) noexcept {
-      return (ready.fetch_and(~task_id) & task_id);
-    }
-
-    //! Mark id as completed, and synchronize with waiting threads
-    void mark_completed(id task_id) noexcept;
-
-    //! Tell all unstarted functions in region to return immediately
-    void abort() noexcept;
-
-    //! Blocks until all functions in region have aborted or completed.
-    void wait() noexcept;
-
-    //! Same as `wait()`, except `this_thread` runs tasks while waiting.
-    void wait(thread_group& threads) noexcept;
-
-  private:
-    /* This implementation is a bit pessimistic, it ensures that all copies
-    of a wrapped task can only be executed once. `thread_group` should never
-    do this, but some variable needs to track whether an abort should be done
-    anyway... */
-    std::shared_ptr<state> next;
-    std::atomic<id> ready;   //!< Tracks whether a task has been invoked
-    std::atomic<id> pending; //!< Tracks when a task has completed or aborted
-    boost::mutex sync_on_complete;
-    boost::condition_variable all_complete;
-  };
-
-  template<typename F>
-  struct wrapper
-  {
-    wrapper(state::id id_src, std::shared_ptr<state> st_src, F f_src)
-      : task_id(id_src), st(std::move(st_src)), f(std::move(f_src)) {
-    }
-
-    wrapper(const wrapper&) = default;
-    wrapper(wrapper&&) = default;
-    wrapper& operator=(const wrapper&) = default;
-    wrapper& operator=(wrapper&&) = default;
-
-    void operator()() {
-      if (st) {
-        if (st->can_run(task_id)) {
-          f();
-        }
-        st->mark_completed(task_id);
-      }
-    }
-
-  private:
-    const state::id task_id;
-    std::shared_ptr<state> st;
-    F f;
-  };
-
-public:
-  friend struct task_region_;
-
-  task_region_handle() = delete;
-  task_region_handle(const task_region_handle&) = delete;
-  task_region_handle(task_region_handle&&) = delete;
-
-  //! Cancels unstarted pending tasks, and waits for them to respond.
-  ~task_region_handle() noexcept {
-    if (st) {
-      st->abort();
-      st->wait(threads);
-    }
-  }
-
-  task_region_handle& operator=(const task_region_handle&) = delete;
-  task_region_handle& operator=(task_region_handle&&) = delete;
-
-  /*! If the group has no threads, `f` is immediately run before returning.
-  Otherwise, `f` is dispatched to the thread_group associated with `this`
-  region. If `f` is dispatched to another thread, and it throws, the process
-  will immediately terminate. See std::packaged_task for getting exceptions on
-  functions executed on other threads. */
-  template<typename F>
-  void run(F&& f) {
-    if (threads.count() == 0) {
-      f();
-    } else {
-      if (!st || next_id == 0) {
-        create_state();
-      }
-      const state::id this_id = next_id;
-      next_id <<= 1;
-
-      st->track_id(this_id);
-      threads.dispatch(wrapper<F>{this_id, st, std::move(f)});
-    }
-  }
-
-  //! Wait until all functions provided to `run` have completed.
-  void wait() noexcept {
-    if (st) {
-      do_wait();
-    }
-  }
- 
-private:
-  explicit task_region_handle(thread_group& threads_src)
-    : st(nullptr), threads(threads_src), next_id(0) {
-  }
-
-  void create_state();
-  void do_wait() noexcept;
-
-  std::shared_ptr<state> st;
-  thread_group& threads;
-  state::id next_id;
-};
-
-/*! Function for creating a `task_region_handle`, which automatically calls
-`task_region_handle::wait()` before returning. If a `thread_group` is not
-provided, one is created with an optimal number of threads. The callback `f`
-must have the signature `void(task_region_handle&)`. */
-struct task_region_ {
-  template<typename F>
-  void operator()(thread_group& threads, F&& f) const {
-    static_assert(
-      std::is_same<void, typename std::result_of<F(task_region_handle&)>::type>::value,
-      "f cannot have a return value"
-    );
-    task_region_handle region{threads};
-    f(region);
-    region.wait();
-  }
-
-  template<typename F>
-  void operator()(thread_group&& threads, F&& f) const {
-    (*this)(threads, std::forward<F>(f));
-  }
-
-  template<typename F>
-  void operator()(F&& f) const {
-    thread_group threads;
-    (*this)(threads, std::forward<F>(f));
-  }
-};
-
-constexpr const task_region_ task_region{};
-}
diff --git a/src/common/thread_group.cpp b/src/common/thread_group.cpp
deleted file mode 100644
index 691a27a25..000000000
--- a/src/common/thread_group.cpp
+++ /dev/null
@@ -1,153 +0,0 @@
-// Copyright (c) 2014-2017, The Monero Project
-//
-// All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without modification, are
-// permitted provided that the following conditions are met:
-//
-// 1. Redistributions of source code must retain the above copyright notice, this list of
-//    conditions and the following disclaimer.
-//
-// 2. Redistributions in binary form must reproduce the above copyright notice, this list
-//    of conditions and the following disclaimer in the documentation and/or other
-//    materials provided with the distribution.
-//
-// 3. Neither the name of the copyright holder nor the names of its contributors may be
-//    used to endorse or promote products derived from this software without specific
-//    prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
-// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
-// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
-// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#include "common/thread_group.h"
-
-#include <boost/thread/locks.hpp>
-#include <cassert>
-#include <limits>
-#include <stdexcept>
-
-#include "cryptonote_config.h"
-#include "common/util.h"
-
-namespace tools
-{
-std::size_t thread_group::optimal() {
-  static_assert(
-    std::numeric_limits<unsigned>::max() <= std::numeric_limits<std::size_t>::max(), 
-    "unexpected truncation"
-  );
-  const std::size_t hardware = get_max_concurrency();
-  return hardware ? (hardware - 1) : 0;
-}
-
-std::size_t thread_group::optimal_with_max(std::size_t count) {
-  return count ? std::min(count - 1, optimal()) : 0;
-}
-
-thread_group::thread_group(std::size_t count) : internal() {
-  if (count) {
-    internal.emplace(count);
-  }
-}
-
-thread_group::data::data(std::size_t count)
-  : threads()
-  , head{nullptr}
-  , last(std::addressof(head))
-  , mutex()
-  , has_work()
-  , stop(false) {
-  threads.reserve(count);
-  boost::thread::attributes attrs;
-  attrs.set_stack_size(THREAD_STACK_SIZE);
-  while (count--) {
-    threads.push_back(boost::thread(attrs, boost::bind(&thread_group::data::run, this)));
-  }
-}
-
-thread_group::data::~data() noexcept {
-  {
-    const boost::unique_lock<boost::mutex> lock(mutex);
-    stop = true;
-  }
-  has_work.notify_all();
-  for (auto& worker : threads) {
-    try {
-      worker.join();
-    }
-    catch(...) {}
-  }
-}
-
-std::unique_ptr<thread_group::data::work> thread_group::data::get_next() noexcept {
-  std::unique_ptr<work> rc = std::move(head.ptr);
-  if (rc != nullptr) {
-    head.ptr = std::move(rc->next.ptr);
-    if (head.ptr == nullptr) {
-      last = std::addressof(head);
-    }
-  }
-  return rc;
-}
-
-bool thread_group::data::try_run_one() noexcept {
-  /* This function and `run()` can both throw when acquiring the lock, or in
-  dispatched function. It is tough to recover from either, particularly the
-  lock case. These functions are marked as noexcept so that if either call
-  throws, the entire process is terminated. Users of the `dispatch` call are
-  expected to make their functions noexcept, or use std::packaged_task to copy
-  exceptions so that the process will continue in all but the most pessimistic
-  cases (std::bad_alloc). This was the existing behavior;
-  `asio::io_service::run` propogates errors from dispatched calls, and uncaught
-  exceptions on threads result in process termination. */
-  std::unique_ptr<work> next = nullptr;
-  {
-    const boost::unique_lock<boost::mutex> lock(mutex);
-    next = get_next();
-  }
-  if (next) {
-    assert(next->f);
-    next->f();
-    return true;
-  }
-  return false;
-}
-
-void thread_group::data::run() noexcept {
-  // see `try_run_one()` source for additional information
-  while (true) {
-    std::unique_ptr<work> next = nullptr;
-    {
-      boost::unique_lock<boost::mutex> lock(mutex);
-      has_work.wait(lock, [this] { return head.ptr != nullptr || stop; });
-      if (stop) {
-        return;
-      }
-      next = get_next();
-    }
-    assert(next != nullptr);
-    assert(next->f);
-    next->f();
-  }
-}
-
-void thread_group::data::dispatch(std::function<void()> f) {
-  std::unique_ptr<work> latest(new work{std::move(f), node{nullptr}});
-  node* const latest_node = std::addressof(latest->next);
-  {
-    const boost::unique_lock<boost::mutex> lock(mutex);
-    assert(last != nullptr);
-    assert(last->ptr == nullptr);
-
-    last->ptr = std::move(latest);
-    last = latest_node;
-  }
-  has_work.notify_one(); 
-}
-}
diff --git a/src/common/thread_group.h b/src/common/thread_group.h
deleted file mode 100644
index 48fd4cd56..000000000
--- a/src/common/thread_group.h
+++ /dev/null
@@ -1,143 +0,0 @@
-// Copyright (c) 2014-2017, The Monero Project
-// 
-// All rights reserved.
-// 
-// Redistribution and use in source and binary forms, with or without modification, are
-// permitted provided that the following conditions are met:
-// 
-// 1. Redistributions of source code must retain the above copyright notice, this list of
-//    conditions and the following disclaimer.
-// 
-// 2. Redistributions in binary form must reproduce the above copyright notice, this list
-//    of conditions and the following disclaimer in the documentation and/or other
-//    materials provided with the distribution.
-// 
-// 3. Neither the name of the copyright holder nor the names of its contributors may be
-//    used to endorse or promote products derived from this software without specific
-//    prior written permission.
-// 
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
-// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
-// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
-// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#pragma once
-
-#include <boost/optional/optional.hpp>
-#include <boost/thread/condition_variable.hpp>
-#include <boost/thread/mutex.hpp>
-#include <boost/thread/thread.hpp>
-#include <cstddef>
-#include <functional>
-#include <thread>
-#include <utility>
-#include <vector>
-
-namespace tools 
-{
-//! Manages zero or more threads for work dispatching.
-class thread_group
-{
-public:
-
-  //! \return `get_max_concurrency() ? get_max_concurrency() - 1 : 0`
-  static std::size_t optimal();
-
-  //! \return `count ? min(count - 1, optimal()) : 0`
-  static std::size_t optimal_with_max(std::size_t count);
-
-  //! Create an optimal number of threads.
-  explicit thread_group() : thread_group(optimal()) {}
-
-  //! Create exactly `count` threads.
-  explicit thread_group(std::size_t count);
-
-  thread_group(thread_group const&) = delete;
-  thread_group(thread_group&&) = delete;
-
-  //! Joins threads, but does not necessarily run all dispatched functions.
-  ~thread_group() = default;
-
-  thread_group& operator=(thread_group const&) = delete;
-  thread_group& operator=(thread_group&&) = delete;
-
-  //! \return Number of threads owned by `this` group.
-  std::size_t count() const noexcept {
-    if (internal) {
-      return internal->count();
-    }
-    return 0;
-  }
-
-  //! \return True iff a function was available and executed (on `this_thread`).
-  bool try_run_one() noexcept {
-    if (internal) {
-      return internal->try_run_one();
-    }
-    return false;
-  }
-
-  /*! `f` is invoked immediately if `count() == 0`, otherwise execution of `f`
-  is queued for next available thread. If `f` is queued, any exception leaving
-  that function will result in process termination. Use std::packaged_task if
-  exceptions need to be handled. */
-  template<typename F>
-  void dispatch(F&& f) {
-    if (internal) {
-      internal->dispatch(std::forward<F>(f));
-    }
-    else {
-      f();
-    }
-  }
-
-private:
-  class data {
-  public:
-    data(std::size_t count);
-    ~data() noexcept;
-
-    std::size_t count() const noexcept {
-      return threads.size();
-    }
-
-    bool try_run_one() noexcept;
-    void dispatch(std::function<void()> f);
-
-  private:
-    struct work;
-
-    struct node {
-      std::unique_ptr<work> ptr;
-    };
-
-    struct work {
-      std::function<void()> f;
-      node next;
-    };
-
-    //! Requires lock on `mutex`.
-    std::unique_ptr<work> get_next() noexcept;
-
-    //! Blocks until destructor is invoked, only call from thread.
-    void run() noexcept;
-
-  private:
-    std::vector<boost::thread> threads;
-    node head;
-    node* last;
-    boost::condition_variable has_work;
-    boost::mutex mutex;
-    bool stop;
-  };
-
-private:
-  // optionally construct elements, without separate heap allocation
-  boost::optional<data> internal;
-};
-
-}
diff --git a/src/common/threadpool.cpp b/src/common/threadpool.cpp
new file mode 100644
index 000000000..f7f9bbbaf
--- /dev/null
+++ b/src/common/threadpool.cpp
@@ -0,0 +1,113 @@
+// Copyright (c) 2017, The Monero Project
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#include "common/threadpool.h"
+
+#include <cassert>
+#include <limits>
+#include <stdexcept>
+
+#include "cryptonote_config.h"
+#include "common/util.h"
+
+namespace tools
+{
+threadpool::threadpool() : running(true), active(0) {
+  boost::thread::attributes attrs;
+  attrs.set_stack_size(THREAD_STACK_SIZE);
+  max = tools::get_max_concurrency();
+  size_t i = max;
+  while(i--) {
+    threads.push_back(boost::thread(attrs, boost::bind(&threadpool::run, this)));
+  }
+}
+
+threadpool::~threadpool() {
+  {
+    const boost::unique_lock<boost::mutex> lock(mutex);
+    running = false;
+    has_work.notify_all();
+  }
+  for (size_t i = 0; i<threads.size(); i++) {
+    threads[i].join();
+  }
+}
+
+void threadpool::submit(waiter *obj, std::function<void()> f) {
+  entry e = {obj, f};
+  boost::unique_lock<boost::mutex> lock(mutex);
+  if (active == max && !queue.empty()) {
+    // if all available threads are already running
+    // and there's work waiting, just run in current thread
+    lock.unlock();
+    f();
+  } else {
+    if (obj)
+      obj->inc();
+    queue.push_back(e);
+    has_work.notify_one();
+  }
+}
+
+void threadpool::waiter::wait() {
+  boost::unique_lock<boost::mutex> lock(mt);
+  while(num) cv.wait(lock);
+}
+
+void threadpool::waiter::inc() {
+  const boost::unique_lock<boost::mutex> lock(mt);
+  num++;
+}
+
+void threadpool::waiter::dec() {
+  const boost::unique_lock<boost::mutex> lock(mt);
+  num--;
+  if (!num)
+    cv.notify_one();
+}
+
+void threadpool::run() {
+  boost::unique_lock<boost::mutex> lock(mutex);
+  while (running) {
+    entry e;
+    while(queue.empty() && running)
+      has_work.wait(lock);
+    if (!running) break;
+
+    active++;
+    e = queue.front();
+    queue.pop_front();
+    lock.unlock();
+    e.f();
+
+    if (e.wo)
+      e.wo->dec();
+    lock.lock();
+    active--;
+  }
+}
+}
diff --git a/src/common/threadpool.h b/src/common/threadpool.h
new file mode 100644
index 000000000..9455e9f66
--- /dev/null
+++ b/src/common/threadpool.h
@@ -0,0 +1,87 @@
+// Copyright (c) 2017, The Monero Project
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#pragma once
+
+#include <boost/thread/condition_variable.hpp>
+#include <boost/thread/mutex.hpp>
+#include <boost/thread/thread.hpp>
+#include <cstddef>
+#include <functional>
+#include <utility>
+#include <vector>
+
+namespace tools
+{
+//! A global thread pool
+class threadpool
+{
+public:
+  static threadpool& getInstance() {
+    static threadpool instance;
+    return instance;
+  }
+
+  // The waiter lets the caller know when all of its
+  // tasks are completed.
+  class waiter {
+    boost::mutex mt;
+    boost::condition_variable cv;
+    int num;
+    public:
+    void inc();
+    void dec();
+    void wait();  //! Wait for a set of tasks to finish.
+    waiter() : num(0){}
+    ~waiter() { wait(); }
+  };
+
+  // Submit a task to the pool. The waiter pointer may be
+  // NULL if the caller doesn't care to wait for the
+  // task to finish.
+  void submit(waiter *waiter, std::function<void()> f);
+
+  int get_max_concurrency() { return max; }
+
+  private:
+    threadpool();
+    ~threadpool();
+    typedef struct entry {
+      waiter *wo;
+      std::function<void()> f;
+    } entry;
+    std::deque<entry> queue;
+    boost::condition_variable has_work;
+    boost::mutex mutex;
+    std::vector<boost::thread> threads;
+    int active;
+    int max;
+    bool running;
+    void run();
+};
+
+}
diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index 69d2edf65..7226a19b2 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -45,6 +45,7 @@
 #include "profile_tools.h"
 #include "file_io_utils.h"
 #include "common/int-util.h"
+#include "common/threadpool.h"
 #include "common/boost_serialization_helper.h"
 #include "warnings.h"
 #include "crypto/hash.h"
@@ -2513,33 +2514,9 @@ bool Blockchain::check_tx_inputs(transaction& tx, tx_verification_context &tvc,
   std::vector < uint64_t > results;
   results.resize(tx.vin.size(), 0);
 
-  int threads = tools::get_max_concurrency();
-
-  boost::asio::io_service ioservice;
-  boost::thread_group threadpool;
-  bool ioservice_active = false;
-
-  std::unique_ptr < boost::asio::io_service::work > work(new boost::asio::io_service::work(ioservice));
-  if(threads > 1)
-  {
-    for (int i = 0; i < threads; i++)
-    {
-      threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioservice));
-    }
-    ioservice_active = true;
-  }
-
-#define KILL_IOSERVICE()  \
-        if(ioservice_active) \
-        { \
-            work.reset(); \
-            while (!ioservice.stopped()) ioservice.poll(); \
-            threadpool.join_all(); \
-            ioservice.stop(); \
-            ioservice_active = false; \
-        }
-
-  epee::misc_utils::auto_scope_leave_caller ioservice_killer = epee::misc_utils::create_scope_leave_handler([&]() { KILL_IOSERVICE(); });
+  tools::threadpool& tpool = tools::threadpool::getInstance();
+  tools::threadpool::waiter waiter;
+  int threads = tpool.get_max_concurrency();
 
   for (const auto& txin : tx.vin)
   {
@@ -2600,7 +2577,7 @@ bool Blockchain::check_tx_inputs(transaction& tx, tx_verification_context &tvc,
       {
         // ND: Speedup
         // 1. Thread ring signature verification if possible.
-        ioservice.dispatch(boost::bind(&Blockchain::check_ring_signature, this, std::cref(tx_prefix_hash), std::cref(in_to_key.k_image), std::cref(pubkeys[sig_index]), std::cref(tx.signatures[sig_index]), std::ref(results[sig_index])));
+        tpool.submit(&waiter, boost::bind(&Blockchain::check_ring_signature, this, std::cref(tx_prefix_hash), std::cref(in_to_key.k_image), std::cref(pubkeys[sig_index]), std::cref(tx.signatures[sig_index]), std::ref(results[sig_index])));
       }
       else
       {
@@ -2623,8 +2600,8 @@ bool Blockchain::check_tx_inputs(transaction& tx, tx_verification_context &tvc,
 
     sig_index++;
   }
-
-  KILL_IOSERVICE();
+  if (tx.version == 1 && threads > 1)
+    waiter.wait();
 
   if (tx.version == 1)
   {
@@ -3699,7 +3676,8 @@ bool Blockchain::prepare_handle_incoming_blocks(const std::list<block_complete_e
     return true;
 
   bool blocks_exist = false;
-  uint64_t threads = tools::get_max_concurrency();
+  tools::threadpool& tpool = tools::threadpool::getInstance();
+  uint64_t threads = tpool.get_max_concurrency();
 
   if (blocks_entry.size() > 1 && threads > 1 && m_max_prepare_blocks_threads > 1)
   {
@@ -3708,15 +3686,12 @@ bool Blockchain::prepare_handle_incoming_blocks(const std::list<block_complete_e
       threads = m_max_prepare_blocks_threads;
 
     uint64_t height = m_db->height();
-    std::vector<boost::thread *> thread_list;
     int batches = blocks_entry.size() / threads;
     int extra = blocks_entry.size() % threads;
     MDEBUG("block_batches: " << batches);
     std::vector<std::unordered_map<crypto::hash, crypto::hash>> maps(threads);
     std::vector < std::vector < block >> blocks(threads);
     auto it = blocks_entry.begin();
-    boost::thread::attributes attrs;
-    attrs.set_stack_size(THREAD_STACK_SIZE);
 
     for (uint64_t i = 0; i < threads; i++)
     {
@@ -3775,19 +3750,14 @@ bool Blockchain::prepare_handle_incoming_blocks(const std::list<block_complete_e
     {
       m_blocks_longhash_table.clear();
       uint64_t thread_height = height;
+      tools::threadpool::waiter waiter;
       for (uint64_t i = 0; i < threads; i++)
       {
-        thread_list.push_back(new boost::thread(attrs, boost::bind(&Blockchain::block_longhash_worker, this, thread_height, std::cref(blocks[i]), std::ref(maps[i]))));
+        tpool.submit(&waiter, boost::bind(&Blockchain::block_longhash_worker, this, thread_height, std::cref(blocks[i]), std::ref(maps[i])));
         thread_height += blocks[i].size();
       }
 
-      for (size_t j = 0; j < thread_list.size(); j++)
-      {
-        thread_list[j]->join();
-        delete thread_list[j];
-      }
-
-      thread_list.clear();
+      waiter.wait();
 
       if (m_cancel)
          return false;
@@ -3911,30 +3881,20 @@ bool Blockchain::prepare_handle_incoming_blocks(const std::list<block_complete_e
   // [output] stores all transactions for each tx_out_index::hash found
   std::vector<std::unordered_map<crypto::hash, cryptonote::transaction>> transactions(amounts.size());
 
-  threads = tools::get_max_concurrency();
+  threads = tpool.get_max_concurrency();
   if (!m_db->can_thread_bulk_indices())
     threads = 1;
 
   if (threads > 1)
   {
-    boost::asio::io_service ioservice;
-    boost::thread_group threadpool;
-    std::unique_ptr < boost::asio::io_service::work > work(new boost::asio::io_service::work(ioservice));
-
-    for (uint64_t i = 0; i < threads; i++)
-    {
-      threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioservice));
-    }
+    tools::threadpool::waiter waiter;
 
     for (size_t i = 0; i < amounts.size(); i++)
     {
       uint64_t amount = amounts[i];
-      ioservice.dispatch(boost::bind(&Blockchain::output_scan_worker, this, amount, std::cref(offset_map[amount]), std::ref(tx_map[amount]), std::ref(transactions[i])));
+      tpool.submit(&waiter, boost::bind(&Blockchain::output_scan_worker, this, amount, std::cref(offset_map[amount]), std::ref(tx_map[amount]), std::ref(transactions[i])));
     }
-
-    work.reset();
-    threadpool.join_all();
-    ioservice.stop();
+    waiter.wait();
   }
   else
   {
diff --git a/src/cryptonote_core/cryptonote_core.cpp b/src/cryptonote_core/cryptonote_core.cpp
index c3aeb15f0..903e9661c 100644
--- a/src/cryptonote_core/cryptonote_core.cpp
+++ b/src/cryptonote_core/cryptonote_core.cpp
@@ -37,7 +37,7 @@ using namespace epee;
 #include "common/util.h"
 #include "common/updates.h"
 #include "common/download.h"
-#include "common/task_region.h"
+#include "common/threadpool.h"
 #include "warnings.h"
 #include "crypto/crypto.h"
 #include "cryptonote_config.h"
@@ -74,7 +74,7 @@ namespace cryptonote
               m_last_dns_checkpoints_update(0),
               m_last_json_checkpoints_update(0),
               m_disable_dns_checkpoints(false),
-              m_threadpool(tools::thread_group::optimal()),
+              m_threadpool(tools::threadpool::getInstance()),
               m_update_download(0)
   {
     m_checkpoints_updating.clear();
@@ -591,54 +591,53 @@ namespace cryptonote
     std::vector<result> results(tx_blobs.size());
 
     tvc.resize(tx_blobs.size());
-    tools::task_region(m_threadpool, [&] (tools::task_region_handle& region) {
-      std::list<blobdata>::const_iterator it = tx_blobs.begin();
-      for (size_t i = 0; i < tx_blobs.size(); i++, ++it) {
-        region.run([&, i, it] {
+    tools::threadpool::waiter waiter;
+    std::list<blobdata>::const_iterator it = tx_blobs.begin();
+    for (size_t i = 0; i < tx_blobs.size(); i++, ++it) {
+      m_threadpool.submit(&waiter, [&, i, it] {
+        try
+        {
+          results[i].res = handle_incoming_tx_pre(*it, tvc[i], results[i].tx, results[i].hash, results[i].prefix_hash, keeped_by_block, relayed, do_not_relay);
+        }
+        catch (const std::exception &e)
+        {
+          MERROR_VER("Exception in handle_incoming_tx_pre: " << e.what());
+          results[i].res = false;
+        }
+      });
+    }
+    waiter.wait();
+    it = tx_blobs.begin();
+    for (size_t i = 0; i < tx_blobs.size(); i++, ++it) {
+      if (!results[i].res)
+        continue;
+      if(m_mempool.have_tx(results[i].hash))
+      {
+        LOG_PRINT_L2("tx " << results[i].hash << "already have transaction in tx_pool");
+      }
+      else if(m_blockchain_storage.have_tx(results[i].hash))
+      {
+        LOG_PRINT_L2("tx " << results[i].hash << " already have transaction in blockchain");
+      }
+      else
+      {
+        m_threadpool.submit(&waiter, [&, i, it] {
           try
           {
-            results[i].res = handle_incoming_tx_pre(*it, tvc[i], results[i].tx, results[i].hash, results[i].prefix_hash, keeped_by_block, relayed, do_not_relay);
+            results[i].res = handle_incoming_tx_post(*it, tvc[i], results[i].tx, results[i].hash, results[i].prefix_hash, keeped_by_block, relayed, do_not_relay);
           }
           catch (const std::exception &e)
           {
-            MERROR_VER("Exception in handle_incoming_tx_pre: " << e.what());
+            MERROR_VER("Exception in handle_incoming_tx_post: " << e.what());
             results[i].res = false;
           }
         });
       }
-    });
-    tools::task_region(m_threadpool, [&] (tools::task_region_handle& region) {
-      std::list<blobdata>::const_iterator it = tx_blobs.begin();
-      for (size_t i = 0; i < tx_blobs.size(); i++, ++it) {
-        if (!results[i].res)
-          continue;
-        if(m_mempool.have_tx(results[i].hash))
-        {
-          LOG_PRINT_L2("tx " << results[i].hash << "already have transaction in tx_pool");
-        }
-        else if(m_blockchain_storage.have_tx(results[i].hash))
-        {
-          LOG_PRINT_L2("tx " << results[i].hash << " already have transaction in blockchain");
-        }
-        else
-        {
-          region.run([&, i, it] {
-            try
-            {
-              results[i].res = handle_incoming_tx_post(*it, tvc[i], results[i].tx, results[i].hash, results[i].prefix_hash, keeped_by_block, relayed, do_not_relay);
-            }
-            catch (const std::exception &e)
-            {
-              MERROR_VER("Exception in handle_incoming_tx_post: " << e.what());
-              results[i].res = false;
-            }
-          });
-        }
-      }
-    });
+    }
+    waiter.wait();
 
     bool ok = true;
-    std::list<blobdata>::const_iterator it = tx_blobs.begin();
+    it = tx_blobs.begin();
     for (size_t i = 0; i < tx_blobs.size(); i++, ++it) {
       if (!results[i].res)
       {
diff --git a/src/cryptonote_core/cryptonote_core.h b/src/cryptonote_core/cryptonote_core.h
index 8e17569a9..0a64b4b4a 100644
--- a/src/cryptonote_core/cryptonote_core.h
+++ b/src/cryptonote_core/cryptonote_core.h
@@ -40,7 +40,7 @@
 #include "cryptonote_protocol/cryptonote_protocol_handler_common.h"
 #include "storages/portable_storage_template_helper.h"
 #include "common/download.h"
-#include "common/thread_group.h"
+#include "common/threadpool.h"
 #include "tx_pool.h"
 #include "blockchain.h"
 #include "cryptonote_basic/miner.h"
@@ -940,7 +940,7 @@ namespace cryptonote
      std::unordered_set<crypto::hash> bad_semantics_txes[2];
      boost::mutex bad_semantics_txes_lock;
 
-     tools::thread_group m_threadpool;
+     tools::threadpool& m_threadpool;
 
      enum {
        UPDATES_DISABLED,
diff --git a/src/ringct/rctSigs.cpp b/src/ringct/rctSigs.cpp
index 8efd6a07c..946325367 100644
--- a/src/ringct/rctSigs.cpp
+++ b/src/ringct/rctSigs.cpp
@@ -30,8 +30,7 @@
 
 #include "misc_log_ex.h"
 #include "common/perf_timer.h"
-#include "common/task_region.h"
-#include "common/thread_group.h"
+#include "common/threadpool.h"
 #include "common/util.h"
 #include "rctSigs.h"
 #include "cryptonote_basic/cryptonote_format_utils.h"
@@ -731,17 +730,16 @@ namespace rct {
         try
         {
           if (semantics) {
+            tools::threadpool& tpool = tools::threadpool::getInstance();
+            tools::threadpool::waiter waiter;
             std::deque<bool> results(rv.outPk.size(), false);
-            tools::thread_group threadpool(tools::thread_group::optimal_with_max(rv.outPk.size()));
-
-            tools::task_region(threadpool, [&] (tools::task_region_handle& region) {
-              DP("range proofs verified?");
-              for (size_t i = 0; i < rv.outPk.size(); i++) {
-                region.run([&, i] {
-                  results[i] = verRange(rv.outPk[i].mask, rv.p.rangeSigs[i]);
-                });
-              }
-            });
+            DP("range proofs verified?");
+            for (size_t i = 0; i < rv.outPk.size(); i++) {
+              tpool.submit(&waiter, [&, i] {
+                results[i] = verRange(rv.outPk[i].mask, rv.p.rangeSigs[i]);
+              });
+            }
+            waiter.wait();
 
             for (size_t i = 0; i < rv.outPk.size(); ++i) {
               if (!results[i]) {
@@ -794,7 +792,8 @@ namespace rct {
         const size_t threads = std::max(rv.outPk.size(), rv.mixRing.size());
 
         std::deque<bool> results(threads);
-        tools::thread_group threadpool(tools::thread_group::optimal_with_max(threads));
+        tools::threadpool& tpool = tools::threadpool::getInstance();
+        tools::threadpool::waiter waiter;
 
         if (semantics) {
           key sumOutpks = identity();
@@ -819,13 +818,12 @@ namespace rct {
 
           results.clear();
           results.resize(rv.outPk.size());
-          tools::task_region(threadpool, [&] (tools::task_region_handle& region) {
-            for (size_t i = 0; i < rv.outPk.size(); i++) {
-              region.run([&, i] {
-                  results[i] = verRange(rv.outPk[i].mask, rv.p.rangeSigs[i]);
-              });
-            }
-          });
+          for (size_t i = 0; i < rv.outPk.size(); i++) {
+            tpool.submit(&waiter, [&, i] {
+              results[i] = verRange(rv.outPk[i].mask, rv.p.rangeSigs[i]);
+            });
+          }
+          waiter.wait();
 
           for (size_t i = 0; i < results.size(); ++i) {
             if (!results[i]) {
@@ -839,13 +837,12 @@ namespace rct {
 
           results.clear();
           results.resize(rv.mixRing.size());
-          tools::task_region(threadpool, [&] (tools::task_region_handle& region) {
-            for (size_t i = 0 ; i < rv.mixRing.size() ; i++) {
-              region.run([&, i] {
+          for (size_t i = 0 ; i < rv.mixRing.size() ; i++) {
+            tpool.submit(&waiter, [&, i] {
                 results[i] = verRctMGSimple(message, rv.p.MGs[i], rv.mixRing[i], rv.pseudoOuts[i]);
-              });
-            }
-          });
+            });
+          }
+          waiter.wait();
 
           for (size_t i = 0; i < results.size(); ++i) {
             if (!results[i]) {
diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 323a3a7fe..f72d281c7 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -45,6 +45,7 @@ using namespace epee;
 #include "cryptonote_basic/cryptonote_basic_impl.h"
 #include "common/boost_serialization_helper.h"
 #include "common/command_line.h"
+#include "common/threadpool.h"
 #include "profile_tools.h"
 #include "crypto/crypto.h"
 #include "serialization/binary_utils.h"
@@ -89,14 +90,6 @@ using namespace cryptonote;
 
 #define SECOND_OUTPUT_RELATEDNESS_THRESHOLD 0.0f
 
-#define KILL_IOSERVICE()  \
-    do { \
-      work.reset(); \
-      while (!ioservice.stopped()) ioservice.poll(); \
-      threadpool.join_all(); \
-      ioservice.stop(); \
-    } while(0)
-
 #define KEY_IMAGE_EXPORT_FILE_MAGIC "Monero key image export\002"
 
 namespace
@@ -684,7 +677,9 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
     std::deque<crypto::key_image> ki(tx.vout.size());
     std::deque<uint64_t> amount(tx.vout.size());
     std::deque<rct::key> mask(tx.vout.size());
-    int threads = tools::get_max_concurrency();
+    tools::threadpool& tpool = tools::threadpool::getInstance();
+    tools::threadpool::waiter waiter;
+    int threads = tpool.get_max_concurrency();
     const cryptonote::account_keys& keys = m_account.get_keys();
     crypto::key_derivation derivation;
     generate_key_derivation(tx_pub_key, keys.m_view_secret_key, derivation);
@@ -720,13 +715,6 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
           ++num_vouts_received;
 
           // process the other outs from that tx
-          boost::asio::io_service ioservice;
-          boost::thread_group threadpool;
-          std::unique_ptr < boost::asio::io_service::work > work(new boost::asio::io_service::work(ioservice));
-          for (int i = 0; i < threads; i++)
-          {
-            threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioservice));
-          }
 
           std::vector<uint64_t> money_transfered(tx.vout.size());
           std::deque<bool> error(tx.vout.size());
@@ -734,10 +722,10 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
           // the first one was already checked
           for (size_t i = 1; i < tx.vout.size(); ++i)
           {
-            ioservice.dispatch(boost::bind(&wallet2::check_acc_out_precomp, this, std::cref(keys.m_account_address.m_spend_public_key), std::cref(tx.vout[i]), std::cref(derivation), i,
+            tpool.submit(&waiter, boost::bind(&wallet2::check_acc_out_precomp, this, std::cref(keys.m_account_address.m_spend_public_key), std::cref(tx.vout[i]), std::cref(derivation), i,
               std::ref(received[i]), std::ref(money_transfered[i]), std::ref(error[i])));
           }
-          KILL_IOSERVICE();
+          waiter.wait();
           for (size_t i = 1; i < tx.vout.size(); ++i)
           {
             if (error[i])
@@ -766,23 +754,18 @@ void wallet2::process_new_transaction(const crypto::hash &txid, const cryptonote
     }
     else if (tx.vout.size() > 1 && threads > 1)
     {
-      boost::asio::io_service ioservice;
-      boost::thread_group threadpool;
-      std::unique_ptr < boost::asio::io_service::work > work(new boost::asio::io_service::work(ioservice));
-      for (int i = 0; i < threads; i++)
-      {
-        threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioservice));
-      }
+      tools::threadpool& tpool = tools::threadpool::getInstance();
+      tools::threadpool::waiter waiter;
 
       std::vector<uint64_t> money_transfered(tx.vout.size());
       std::deque<bool> error(tx.vout.size());
       std::deque<bool> received(tx.vout.size());
       for (size_t i = 0; i < tx.vout.size(); ++i)
       {
-        ioservice.dispatch(boost::bind(&wallet2::check_acc_out_precomp, this, std::cref(keys.m_account_address.m_spend_public_key), std::cref(tx.vout[i]), std::cref(derivation), i,
+        tpool.submit(&waiter, boost::bind(&wallet2::check_acc_out_precomp, this, std::cref(keys.m_account_address.m_spend_public_key), std::cref(tx.vout[i]), std::cref(derivation), i,
           std::ref(received[i]), std::ref(money_transfered[i]), std::ref(error[i])));
       }
-      KILL_IOSERVICE();
+      waiter.wait();
       tx_money_got_in_outs = 0;
       for (size_t i = 0; i < tx.vout.size(); ++i)
       {
@@ -1251,7 +1234,8 @@ void wallet2::process_blocks(uint64_t start_height, const std::list<cryptonote::
 
   THROW_WALLET_EXCEPTION_IF(blocks.size() != o_indices.size(), error::wallet_internal_error, "size mismatch");
 
-  int threads = tools::get_max_concurrency();
+  tools::threadpool& tpool = tools::threadpool::getInstance();
+  int threads = tpool.get_max_concurrency();
   if (threads > 1)
   {
     std::vector<crypto::hash> round_block_hashes(threads);
@@ -1262,23 +1246,16 @@ void wallet2::process_blocks(uint64_t start_height, const std::list<cryptonote::
     for (size_t b = 0; b < blocks_size; b += threads)
     {
       size_t round_size = std::min((size_t)threads, blocks_size - b);
-
-      boost::asio::io_service ioservice;
-      boost::thread_group threadpool;
-      std::unique_ptr < boost::asio::io_service::work > work(new boost::asio::io_service::work(ioservice));
-      for (size_t i = 0; i < round_size; i++)
-      {
-        threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioservice));
-      }
+      tools::threadpool::waiter waiter;
 
       std::list<block_complete_entry>::const_iterator tmpblocki = blocki;
       for (size_t i = 0; i < round_size; ++i)
       {
-        ioservice.dispatch(boost::bind(&wallet2::parse_block_round, this, std::cref(tmpblocki->block),
+        tpool.submit(&waiter, boost::bind(&wallet2::parse_block_round, this, std::cref(tmpblocki->block),
           std::ref(round_blocks[i]), std::ref(round_block_hashes[i]), std::ref(error[i])));
         ++tmpblocki;
       }
-      KILL_IOSERVICE();
+      waiter.wait();
       tmpblocki = blocki;
       for (size_t i = 0; i < round_size; ++i)
       {
@@ -1698,7 +1675,8 @@ void wallet2::refresh(uint64_t start_height, uint64_t & blocks_fetched, bool& re
   size_t try_count = 0;
   crypto::hash last_tx_hash_id = m_transfers.size() ? m_transfers.back().m_txid : null_hash;
   std::list<crypto::hash> short_chain_history;
-  boost::thread pull_thread;
+  tools::threadpool& tpool = tools::threadpool::getInstance();
+  tools::threadpool::waiter waiter;
   uint64_t blocks_start_height;
   std::list<cryptonote::block_complete_entry> blocks;
   std::vector<COMMAND_RPC_GET_BLOCKS_FAST::block_output_indices> o_indices;
@@ -1736,11 +1714,11 @@ void wallet2::refresh(uint64_t start_height, uint64_t & blocks_fetched, bool& re
       std::list<cryptonote::block_complete_entry> next_blocks;
       std::vector<cryptonote::COMMAND_RPC_GET_BLOCKS_FAST::block_output_indices> next_o_indices;
       bool error = false;
-      pull_thread = boost::thread([&]{pull_next_blocks(start_height, next_blocks_start_height, short_chain_history, blocks, next_blocks, next_o_indices, error);});
+      tpool.submit(&waiter, [&]{pull_next_blocks(start_height, next_blocks_start_height, short_chain_history, blocks, next_blocks, next_o_indices, error);});
 
       process_blocks(blocks_start_height, blocks, o_indices, added_blocks);
       blocks_fetched += added_blocks;
-      pull_thread.join();
+      waiter.wait();
       if(blocks_start_height == next_blocks_start_height)
       {
         m_node_rpc_proxy.set_height(m_blockchain.size());
@@ -1762,8 +1740,7 @@ void wallet2::refresh(uint64_t start_height, uint64_t & blocks_fetched, bool& re
     catch (const std::exception&)
     {
       blocks_fetched += added_blocks;
-      if (pull_thread.joinable())
-        pull_thread.join();
+      waiter.wait();
       if(try_count < 3)
       {
         LOG_PRINT_L1("Another try pull_blocks (try_count=" << try_count << ")...");
diff --git a/tests/unit_tests/CMakeLists.txt b/tests/unit_tests/CMakeLists.txt
index 2f62dc2aa..f5e08b102 100644
--- a/tests/unit_tests/CMakeLists.txt
+++ b/tests/unit_tests/CMakeLists.txt
@@ -55,7 +55,6 @@ set(unit_tests_sources
   test_tx_utils.cpp
   test_peerlist.cpp
   test_protocol_pack.cpp
-  thread_group.cpp
   hardfork.cpp
   unbound.cpp
   uri.cpp
diff --git a/tests/unit_tests/thread_group.cpp b/tests/unit_tests/thread_group.cpp
deleted file mode 100644
index c0ba3d38b..000000000
--- a/tests/unit_tests/thread_group.cpp
+++ /dev/null
@@ -1,177 +0,0 @@
-// Copyright (c) 2014-2017, The Monero Project
-//
-// All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without modification, are
-// permitted provided that the following conditions are met:
-//
-// 1. Redistributions of source code must retain the above copyright notice, this list of
-//    conditions and the following disclaimer.
-//
-// 2. Redistributions in binary form must reproduce the above copyright notice, this list
-//    of conditions and the following disclaimer in the documentation and/or other
-//    materials provided with the distribution.
-//
-// 3. Neither the name of the copyright holder nor the names of its contributors may be
-//    used to endorse or promote products derived from this software without specific
-//    prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
-// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
-// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
-// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
-// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
-// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-#include "gtest/gtest.h"
-
-#include <atomic>
-#include "common/task_region.h"
-#include "common/thread_group.h"
-
-TEST(ThreadGroup, NoThreads)
-{
-  tools::task_region(tools::thread_group(0), [] (tools::task_region_handle& region) {
-    std::atomic<bool> completed{false};
-    region.run([&] { completed = true; });
-    EXPECT_TRUE(completed);
-  });
-  {
-    tools::thread_group group(0);
-    std::atomic<bool> completed{false};
-    group.dispatch([&] { completed = true; });
-    EXPECT_TRUE(completed);
-  }
-}
-
-TEST(ThreadGroup, OneThread)
-{
-  tools::thread_group group(1);
-
-  for (unsigned i = 0; i < 3; ++i) {
-    std::atomic<bool> completed{false};
-    tools::task_region(group, [&] (tools::task_region_handle& region) {
-      region.run([&] { completed = true; });
-    });
-    EXPECT_TRUE(completed);
-  }
-}
-
-
-TEST(ThreadGroup, UseActiveThreadOnSync)
-{
-  tools::thread_group group(1);
-
-  for (unsigned i = 0; i < 3; ++i) {
-    std::atomic<bool> completed{false};
-    tools::task_region(group, [&] (tools::task_region_handle& region) {
-      region.run([&] { while (!completed); });
-      region.run([&] { completed = true; });
-    });
-    EXPECT_TRUE(completed);
-  }
-}
-
-TEST(ThreadGroup, InOrder)
-{
-  tools::thread_group group(1);
-
-  for (unsigned i = 0; i < 3; ++i) {
-    std::atomic<unsigned> count{0};
-    std::atomic<bool> completed{false};
-    tools::task_region(group, [&] (tools::task_region_handle& region) {
-      region.run([&] { while (!completed); });
-      region.run([&] { if (count == 0) completed = true; });
-      region.run([&] { ++count; });
-    });
-    EXPECT_TRUE(completed);
-    EXPECT_EQ(1u, count);
-  }
-}
-
-TEST(ThreadGroup, TwoThreads)
-{
-  tools::thread_group group(2);
-
-  for (unsigned i = 0; i < 3; ++i) {
-    std::atomic<bool> completed{false};
-    tools::task_region(group, [&] (tools::task_region_handle& region) {
-      region.run([&] { while (!completed); });
-      region.run([&] { while (!completed); });
-      region.run([&] { completed = true; });
-    });
-    EXPECT_TRUE(completed);
-  }
-}
-
-TEST(ThreadGroup, Nested) {
-  struct fib {
-    unsigned operator()(tools::thread_group& group, unsigned value) const {
-      if (value == 0 || value == 1) {
-        return value;
-      }
-      unsigned left = 0;
-      unsigned right = 0;
-      tools::task_region(group, [&, value] (tools::task_region_handle& region) {
-        region.run([&, value] { left = fib{}(group, value - 1); });
-        region.run([&, value] { right = fib{}(group, value - 2); } );
-      });
-      return left + right;
-    }
-
-    unsigned operator()(tools::thread_group&& group, unsigned value) const {
-      return (*this)(group, value);
-    }
-  };
-  // be careful of depth on asynchronous version
-  EXPECT_EQ(6765, fib{}(tools::thread_group(0), 20));
-  EXPECT_EQ(377, fib{}(tools::thread_group(1), 14));
-}
-
-TEST(ThreadGroup, Many)
-{
-  tools::thread_group group(1);
-
-  for (unsigned i = 0; i < 3; ++i) {
-    std::atomic<unsigned> count{0};
-    tools::task_region(group, [&] (tools::task_region_handle& region) {
-      for (unsigned tasks = 0; tasks < 1000; ++tasks) {
-        region.run([&] { ++count; });
-      }
-    });
-    EXPECT_EQ(1000u, count);
-  }
-}
-
-TEST(ThreadGroup, ThrowInTaskRegion)
-{
-  class test_exception final : std::exception {
-  public:
-    explicit test_exception() : std::exception() {}
-
-    virtual const char* what() const noexcept override {
-      return "test_exception";
-    }
-  };
-
-  tools::thread_group group(1);
-
-  for (unsigned i = 0; i < 3; ++i) {
-    std::atomic<unsigned> count{0};
-    EXPECT_THROW(
-      [&] {
-        tools::task_region(group, [&] (tools::task_region_handle& region) {
-          for (unsigned tasks = 0; tasks < 1000; ++tasks) {
-            region.run([&] { ++count; });
-          }
-          throw test_exception();
-        });
-      }(),
-      test_exception
-    );
-    EXPECT_GE(1000u, count);
-  }
-}