r1

src/scheduler.cpp

@@ -0,0 +1,133 @@
+// Copyright (c) 2015 The Bitcoin Core developers
+// Copyright (c) 2017-2018 The PIVX developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "scheduler.h"
+
+#include "reverselock.h"
+
+#include <assert.h>
+#include <boost/bind.hpp>
+#include <utility>
+
+CScheduler::CScheduler() : nThreadsServicingQueue(0), stopRequested(false), stopWhenEmpty(false)
+{
+}
+
+CScheduler::~CScheduler()
+{
+    assert(nThreadsServicingQueue == 0);
+}
+
+
+#if BOOST_VERSION < 105000
+static boost::system_time toPosixTime(const boost::chrono::system_clock::time_point& t)
+{
+    return boost::posix_time::from_time_t(boost::chrono::system_clock::to_time_t(t));
+}
+#endif
+
+void CScheduler::serviceQueue()
+{
+    boost::unique_lock<boost::mutex> lock(newTaskMutex);
+    ++nThreadsServicingQueue;
+
+    // newTaskMutex is locked throughout this loop EXCEPT
+    // when the thread is waiting or when the user's function
+    // is called.
+    while (!shouldStop()) {
+        try {
+            while (!shouldStop() && taskQueue.empty()) {
+                // Wait until there is something to do.
+                newTaskScheduled.wait(lock);
+            }
+
+            // Wait until either there is a new task, or until
+            // the time of the first item on the queue:
+
+// wait_until needs boost 1.50 or later; older versions have timed_wait:
+#if BOOST_VERSION < 105000
+            while (!shouldStop() && !taskQueue.empty() &&
+                   newTaskScheduled.timed_wait(lock, toPosixTime(taskQueue.begin()->first))) {
+                // Keep waiting until timeout
+            }
+#else
+            // Some boost versions have a conflicting overload of wait_until that returns void.
+            // Explicitly use a template here to avoid hitting that overload.
+            while (!shouldStop() && !taskQueue.empty() &&
+                   newTaskScheduled.wait_until<>(lock, taskQueue.begin()->first) != boost::cv_status::timeout) {
+                // Keep waiting until timeout
+            }
+#endif
+            // If there are multiple threads, the queue can empty while we're waiting (another
+            // thread may service the task we were waiting on).
+            if (shouldStop() || taskQueue.empty())
+                continue;
+
+            Function f = taskQueue.begin()->second;
+            taskQueue.erase(taskQueue.begin());
+
+            {
+                // Unlock before calling f, so it can reschedule itself or another task
+                // without deadlocking:
+                reverse_lock<boost::unique_lock<boost::mutex> > rlock(lock);
+                f();
+            }
+        } catch (...) {
+            --nThreadsServicingQueue;
+            throw;
+        }
+    }
+    --nThreadsServicingQueue;
+    newTaskScheduled.notify_one();
+}
+
+void CScheduler::stop(bool drain)
+{
+    {
+        boost::unique_lock<boost::mutex> lock(newTaskMutex);
+        if (drain)
+            stopWhenEmpty = true;
+        else
+            stopRequested = true;
+    }
+    newTaskScheduled.notify_all();
+}
+
+void CScheduler::schedule(CScheduler::Function f, boost::chrono::system_clock::time_point t)
+{
+    {
+        boost::unique_lock<boost::mutex> lock(newTaskMutex);
+        taskQueue.insert(std::make_pair(t, f));
+    }
+    newTaskScheduled.notify_one();
+}
+
+void CScheduler::scheduleFromNow(CScheduler::Function f, int64_t deltaSeconds)
+{
+    schedule(f, boost::chrono::system_clock::now() + boost::chrono::seconds(deltaSeconds));
+}
+
+static void Repeat(CScheduler* s, CScheduler::Function f, int64_t deltaSeconds)
+{
+    f();
+    s->scheduleFromNow(boost::bind(&Repeat, s, f, deltaSeconds), deltaSeconds);
+}
+
+void CScheduler::scheduleEvery(CScheduler::Function f, int64_t deltaSeconds)
+{
+    scheduleFromNow(boost::bind(&Repeat, this, f, deltaSeconds), deltaSeconds);
+}
+
+size_t CScheduler::getQueueInfo(boost::chrono::system_clock::time_point &first,
+                             boost::chrono::system_clock::time_point &last) const
+{
+    boost::unique_lock<boost::mutex> lock(newTaskMutex);
+    size_t result = taskQueue.size();
+    if (!taskQueue.empty()) {
+        first = taskQueue.begin()->first;
+        last = taskQueue.rbegin()->first;
+    }
+    return result;
+}