adding thread_group for managing async tasks

4 files changed, 351 insertions, 100 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 4b6149cbd..d5d22bca6 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -32,7 +32,8 @@ set(common_sources
   dns_utils.cpp
   util.cpp
   i18n.cpp
-  perf_timer.cpp)
+  perf_timer.cpp
+  thread_group.cpp)
 
 if (STACK_TRACE)
   list(APPEND common_sources stack_trace.cpp)
@@ -55,7 +56,8 @@ set(common_private_headers
   varint.h
   i18n.h
   perf_timer.h
-  stack_trace.h)
+  stack_trace.h
+  thread_group.h)
 
 monero_private_headers(common
   ${common_private_headers})
diff --git a/src/common/thread_group.cpp b/src/common/thread_group.cpp
new file mode 100644
index 000000000..ece268ab7
--- /dev/null
+++ b/src/common/thread_group.cpp
@@ -0,0 +1,164 @@
+// Copyright (c) 2014-2016, 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 <cassert>
+#include <limits>
+#include <stdexcept>
+
+#include "common/util.h"
+
+namespace tools
+{
+thread_group::thread_group(std::size_t count) : internal() {
+  static_assert(
+    std::numeric_limits<unsigned>::max() <= std::numeric_limits<std::size_t>::max(), 
+    "unexpected truncation"
+  );
+  count = std::min<std::size_t>(count, get_max_concurrency());
+  count = count ? count - 1 : 0;
+
+  if (count) {
+    internal.emplace(count);
+  }
+}
+
+thread_group::data::data(std::size_t count)
+  : threads()
+  , head{nullptr}
+  , last(std::addressof(head))
+  , pending(count)
+  , mutex()
+  , has_work()
+  , finished_work()
+  , stop(false) {
+  threads.reserve(count);
+  while (count--) {
+    threads.push_back(std::thread(&thread_group::data::run, this));
+  }
+}
+
+thread_group::data::~data() noexcept {
+  {
+    const std::unique_lock<std::mutex> lock(mutex);
+    stop = true;
+  }
+  has_work.notify_all();
+  finished_work.notify_all();
+  for (auto& worker : threads) {
+    try {
+      worker.join();
+    }
+    catch(...) {}
+  }
+}
+
+
+void thread_group::data::sync() noexcept {
+  /* This function and `run()` can both throw when acquiring the lock, or in
+  the 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. */
+  assert(!threads.empty());
+  bool not_first = false;
+  while (true) {
+    std::unique_ptr<work> next = nullptr;
+    {
+      std::unique_lock<std::mutex> lock(mutex);
+      pending -= std::size_t(not_first);
+      not_first = true;
+      finished_work.notify_all();
+
+      if (stop) {
+        return;
+      }
+
+      next = get_next();
+      if (next == nullptr) {
+        finished_work.wait(lock, [this] { return pending == 0 || stop; });
+        return;
+      }
+    }
+    assert(next->f);
+    next->f();
+  }
+}
+
+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;
+}
+
+void thread_group::data::run() noexcept {
+  // see `sync()` source for additional information
+  while (true) {
+    std::unique_ptr<work> next = nullptr;
+    {
+      std::unique_lock<std::mutex> lock(mutex);
+      --pending;
+      finished_work.notify_all();
+      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 std::unique_lock<std::mutex> lock(mutex);
+    assert(last != nullptr);
+    assert(last->next == nullptr);
+    if (pending == std::numeric_limits<std::size_t>::max()) {
+      throw std::overflow_error("thread_group exceeded max queue depth");
+    }
+    last->ptr = std::move(latest);
+    last = latest_node;
+    ++pending;
+  }
+  has_work.notify_one(); 
+}
+}
diff --git a/src/common/thread_group.h b/src/common/thread_group.h
new file mode 100644
index 000000000..d8461d49a
--- /dev/null
+++ b/src/common/thread_group.h
@@ -0,0 +1,133 @@
+// Copyright (c) 2014-2016, 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 <boost/optional/optional.hpp>
+#include <condition_variable>
+#include <cstddef>
+#include <functional>
+#include <thread>
+#include <utility>
+#include <vector>
+
+namespace tools 
+{
+//! Manages zero or more threads for work dispatching
+class thread_group
+{
+public:
+  //! Create `min(count, get_max_concurrency()) - 1`  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;
+
+  /*! Blocks until all functions provided to `dispatch` complete. Does not
+  destroy threads. If a dispatched function calls `this->dispatch(...)`,
+  `this->sync()` will continue to block until that new function completes. */
+  void sync() noexcept {
+    if (internal) {
+      internal->sync();
+    }
+  }
+
+  /*! Example usage:
+    std::unique_ptr<thread_group, thread_group::lazy_sync> sync(std::addressof(group));
+  which guarantees synchronization before the unique_ptr destructor returns. */
+  struct lazy_sync {
+    void operator()(thread_group* group) const noexcept {
+      if (group != nullptr) {
+        group->sync();
+      }
+    }
+  };
+
+  /*! `f` is invoked immediately if the thread_group is empty, 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;
+
+    void sync() noexcept;
+
+    void dispatch(std::function<void()> f);
+
+  private:
+    struct work;
+
+    struct node {
+      node() = delete;
+      std::unique_ptr<work> ptr;
+    };
+
+    struct work {
+      work() = delete;
+      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<std::thread> threads;
+    node head;
+    node* last;
+    std::size_t pending;
+    std::condition_variable has_work;
+    std::condition_variable finished_work;
+    std::mutex mutex;
+    bool stop;
+  };
+
+private:
+  // optionally construct elements, without separate heap allocation
+  boost::optional<data> internal;
+};
+}
diff --git a/src/ringct/rctSigs.cpp b/src/ringct/rctSigs.cpp
index 19e9d291e..df33c26b2 100644
--- a/src/ringct/rctSigs.cpp
+++ b/src/ringct/rctSigs.cpp
@@ -28,9 +28,9 @@
 // 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 <boost/asio.hpp>
 #include "misc_log_ex.h"
 #include "common/perf_timer.h"
+#include "common/thread_group.h"
 #include "common/util.h"
 #include "rctSigs.h"
 #include "cryptonote_core/cryptonote_format_utils.h"
@@ -38,17 +38,22 @@
 using namespace crypto;
 using namespace std;
 
-#define KILL_IOSERVICE()  \
-        if(ioservice_active) \
-        { \
-            work.reset(); \
-            while (!ioservice.stopped()) ioservice.poll(); \
-            threadpool.join_all(); \
-            ioservice.stop(); \
-            ioservice_active = false; \
+namespace rct {
+    namespace {
+      struct verRangeWrapper_ {
+        void operator()(const key & C, const rangeSig & as, bool &result) const {
+          result = verRange(C, as);
         }
+      };
+      constexpr const verRangeWrapper_ verRangeWrapper{};
 
-namespace rct {
+      struct verRctMGSimpleWrapper_ {
+        void operator()(const key &message, const mgSig &mg, const ctkeyV & pubs, const key & C, bool &result) const {
+          result = verRctMGSimple(message, mg, pubs, C);
+        }
+      };
+      constexpr const verRctMGSimpleWrapper_ verRctMGSimpleWrapper{};
+    }
     
     //Schnorr Non-linkable
     //Gen Gives a signature (L1, s1, s2) proving that the sender knows "x" such that xG = one of P1 or P2
@@ -360,10 +365,6 @@ namespace rct {
         return true;
     }
 
-    void verRangeWrapper(const key & C, const rangeSig & as, bool &result) {
-      result = verRange(C, as);
-    }
-
     key get_pre_mlsag_hash(const rctSig &rv)
     {
       keyV hashes;
@@ -544,9 +545,6 @@ namespace rct {
             return MLSAG_Ver(message, M, mg, rows);
     }
 
-    void verRctMGSimpleWrapper(const key &message, const mgSig &mg, const ctkeyV & pubs, const key & C, bool &result) {
-      result = verRctMGSimple(message, mg, pubs, C);
-    }
 
     //These functions get keys from blockchain
     //replace these when connecting blockchain
@@ -767,38 +765,20 @@ namespace rct {
         // some rct ops can throw
         try
         {
-          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));
-          size_t threads = tools::get_max_concurrency();
-          threads = std::min(threads, rv.outPk.size());
-          for (size_t i = 0; i < threads; ++i)
-            threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioservice));
-          bool ioservice_active = true;
           std::deque<bool> results(rv.outPk.size(), false);
-          epee::misc_utils::auto_scope_leave_caller ioservice_killer = epee::misc_utils::create_scope_leave_handler([&]() { KILL_IOSERVICE(); });
+          tools::thread_group threadpool(rv.outPk.size()); // this must destruct before results
 
           DP("range proofs verified?");
           for (size_t i = 0; i < rv.outPk.size(); i++) {
-              if (threads > 1) {
-                ioservice.dispatch(boost::bind(&verRangeWrapper, std::cref(rv.outPk[i].mask), std::cref(rv.p.rangeSigs[i]), std::ref(results[i])));
-              }
-              else {
-                bool tmp = verRange(rv.outPk[i].mask, rv.p.rangeSigs[i]);
-                DP(tmp);
-                if (!tmp) {
-                  LOG_ERROR("Range proof verification failed for input " << i);
-                  return false;
-                }
-              }
+            threadpool.dispatch(
+              std::bind(verRangeWrapper, std::cref(rv.outPk[i].mask), std::cref(rv.p.rangeSigs[i]), std::ref(results[i]))
+            );
           }
-          KILL_IOSERVICE();
-          if (threads > 1) {
-            for (size_t i = 0; i < rv.outPk.size(); ++i) {
-              if (!results[i]) {
-                LOG_ERROR("Range proof verified failed for input " << i);
-                return false;
-              }
+          threadpool.sync();
+          for (size_t i = 0; i < rv.outPk.size(); ++i) {
+            if (!results[i]) {
+              LOG_ERROR("Range proof verified failed for input " << i);
+              return false;
             }
           }
 
@@ -832,34 +812,23 @@ namespace rct {
         CHECK_AND_ASSERT_MES(rv.pseudoOuts.size() == rv.p.MGs.size(), false, "Mismatched sizes of rv.pseudoOuts and rv.p.MGs");
         CHECK_AND_ASSERT_MES(rv.pseudoOuts.size() == rv.mixRing.size(), false, "Mismatched sizes of rv.pseudoOuts and mixRing");
 
+        const size_t threads = std::max(rv.outPk.size(), rv.mixRing.size());
+        tools::thread_group threadpool(threads);
         {
-          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));
-          size_t threads = tools::get_max_concurrency();
-          threads = std::min(threads, rv.outPk.size());
-          for (size_t i = 0; i < threads; ++i)
-            threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioservice));
-          bool ioservice_active = true;
           std::deque<bool> results(rv.outPk.size(), false);
-          epee::misc_utils::auto_scope_leave_caller ioservice_killer = epee::misc_utils::create_scope_leave_handler([&]() { KILL_IOSERVICE(); });
-
-          for (i = 0; i < rv.outPk.size(); i++) {
-            if (threads > 1) {
-              ioservice.dispatch(boost::bind(&verRangeWrapper, std::cref(rv.outPk[i].mask), std::cref(rv.p.rangeSigs[i]), std::ref(results[i])));
-            }
-            else if (!verRange(rv.outPk[i].mask, rv.p.rangeSigs[i])) {
-                LOG_ERROR("Range proof verified failed for input " << i);
-                return false;
+          {
+            const std::unique_ptr<tools::thread_group, tools::thread_group::lazy_sync> 
+              sync(std::addressof(threadpool));
+            for (i = 0; i < rv.outPk.size(); i++) {
+              threadpool.dispatch(
+                std::bind(verRangeWrapper, std::cref(rv.outPk[i].mask), std::cref(rv.p.rangeSigs[i]), std::ref(results[i]))
+              );
             }
-          }
-          KILL_IOSERVICE();
-          if (threads > 1) {
-            for (size_t i = 0; i < rv.outPk.size(); ++i) {
-              if (!results[i]) {
-                LOG_ERROR("Range proof verified failed for input " << i);
-                return false;
-              }
+          } // threadpool.sync();
+          for (size_t i = 0; i < rv.outPk.size(); ++i) {
+            if (!results[i]) {
+              LOG_ERROR("Range proof verified failed for input " << i);
+              return false;
             }
           }
         }
@@ -875,37 +844,20 @@ namespace rct {
         key message = get_pre_mlsag_hash(rv);
 
         {
-          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));
-          size_t threads = tools::get_max_concurrency();
-          threads = std::min(threads, rv.mixRing.size());
-          for (size_t i = 0; i < threads; ++i)
-            threadpool.create_thread(boost::bind(&boost::asio::io_service::run, &ioservice));
-          bool ioservice_active = true;
           std::deque<bool> results(rv.mixRing.size(), false);
-          epee::misc_utils::auto_scope_leave_caller ioservice_killer = epee::misc_utils::create_scope_leave_handler([&]() { KILL_IOSERVICE(); });
-
-          for (i = 0 ; i < rv.mixRing.size() ; i++) {
-            if (threads > 1) {
-                ioservice.dispatch(boost::bind(&verRctMGSimpleWrapper, std::cref(message), std::cref(rv.p.MGs[i]), std::cref(rv.mixRing[i]), std::cref(rv.pseudoOuts[i]), std::ref(results[i])));
+          {
+            const std::unique_ptr<tools::thread_group, tools::thread_group::lazy_sync>
+              sync(std::addressof(threadpool));
+            for (i = 0 ; i < rv.mixRing.size() ; i++) {
+              threadpool.dispatch(
+                std::bind(verRctMGSimpleWrapper, std::cref(message), std::cref(rv.p.MGs[i]), std::cref(rv.mixRing[i]), std::cref(rv.pseudoOuts[i]), std::ref(results[i]))
+              );
             }
-            else {
-                bool tmpb = verRctMGSimple(message, rv.p.MGs[i], rv.mixRing[i], rv.pseudoOuts[i]);
-                DP(tmpb);
-                if (!tmpb) {
-                    LOG_ERROR("verRctMGSimple failed for input " << i);
-                    return false;
-                }
-            }
-          }
-          KILL_IOSERVICE();
-          if (threads > 1) {
-            for (size_t i = 0; i < results.size(); ++i) {
-              if (!results[i]) {
-                LOG_ERROR("verRctMGSimple failed for input " << i);
-                return false;
-              }
+          } // threadpool.sync();
+          for (size_t i = 0; i < results.size(); ++i) {
+            if (!results[i]) {
+              LOG_ERROR("verRctMGSimple failed for input " << i);
+              return false;
             }
           }
         }