From ff5c8a9034026a6d3ae437fa89c9f3cb9a1ba022 Mon Sep 17 00:00:00 2001
From: Alan Conway <aconway@apache.org>
Date: Fri, 3 Oct 2008 20:56:38 +0000
Subject: Cluster join & brain-dumps working.

cluster: improved join protocol, fixed race conditions.
client/ConnectionHandler,ConnectionImpl: fixed connection close race causing client hang.
src/qpid/sys/PollableQueue.h: fixed incorrect use of startWatch/stopWatch.


git-svn-id: https://svn.apache.org/repos/asf/incubator/qpid/trunk/qpid@701532 13f79535-47bb-0310-9956-ffa450edef68
---
 cpp/src/qpid/sys/PollableQueue.h | 99 ++++++++++++++++++++--------------------
 1 file changed, 49 insertions(+), 50 deletions(-)

(limited to 'cpp/src/qpid/sys/PollableQueue.h')

diff --git a/cpp/src/qpid/sys/PollableQueue.h b/cpp/src/qpid/sys/PollableQueue.h
index 3a94c60be0..8313196623 100644
--- a/cpp/src/qpid/sys/PollableQueue.h
+++ b/cpp/src/qpid/sys/PollableQueue.h
@@ -42,40 +42,31 @@ class Poller;
  */
 template <class T>
 class PollableQueue {
-    typedef std::deque<T> Queue;
-
   public:
-    typedef typename Queue::iterator iterator;
-    
     /** Callback to process a range of items. */
-    typedef boost::function<void (const iterator&, const iterator&)> Callback;
+    typedef boost::function<void (const T&)> Callback;
 
-    /** @see forEach() */
-    template <class F> struct ForEach {
-        F handleOne;
-        ForEach(F f) : handleOne(f) {}
-        void operator()(const iterator& i, const iterator& j) const { std::for_each(i, j, handleOne); }
-    };
-
-    /** Create a range callback from a functor that processes a single item. */
-    template <class F> static ForEach<F> forEach(const F& f) { return ForEach<F>(f); }
-    
     /** When the queue is selected by the poller, values are passed to callback cb. */
-    explicit PollableQueue(const Callback& cb);
+    PollableQueue(const Callback& cb, const boost::shared_ptr<sys::Poller>& poller);
 
+    ~PollableQueue();
+    
     /** Push a value onto the queue. Thread safe */
     void push(const T& t);
 
     /** Start polling. */ 
-    void start(const boost::shared_ptr<sys::Poller>& poller);
+    void start();
 
     /** Stop polling and wait for the current callback, if any, to complete. */
     void stop();
 
     /** Are we currently stopped?*/
-    bool isStopped() const;
-    
+    bool isStopped() const { ScopedLock l(lock); return stopped; }
+
+    size_t size() { ScopedLock l(lock); return queue.size(); }
+    bool empty() { ScopedLock l(lock); return queue.empty(); }
   private:
+    typedef std::deque<T> Queue;
     typedef sys::Monitor::ScopedLock ScopedLock;
     typedef sys::Monitor::ScopedUnlock ScopedUnlock;
 
@@ -83,59 +74,67 @@ class PollableQueue {
     
     mutable sys::Monitor lock;
     Callback callback;
+    boost::shared_ptr<sys::Poller> poller;
     PollableCondition condition;
-    sys::DispatchHandle handle;
+    DispatchHandle handle;
     Queue queue;
-    Queue batch;
-    bool dispatching, stopped;
+    Thread dispatcher;
+    bool stopped;
 };
 
-template <class T> PollableQueue<T>::PollableQueue(const Callback& cb) // FIXME aconway 2008-08-12: 
-    : callback(cb),
-      handle(condition, boost::bind(&PollableQueue<T>::dispatch, this, _1), 0, 0),
-      dispatching(false), stopped(true)
-{}
+template <class T> PollableQueue<T>::PollableQueue(
+    const Callback& cb, const boost::shared_ptr<sys::Poller>& p) 
+    : callback(cb), poller(p),
+      handle(condition, boost::bind(&PollableQueue<T>::dispatch, this, _1), 0, 0), stopped(true)
+{
+    handle.startWatch(poller);
+    handle.unwatch();
+}
 
-template <class T> void PollableQueue<T>::start(const boost::shared_ptr<sys::Poller>& poller) {
+template <class T> void PollableQueue<T>::start() {
     ScopedLock l(lock);
+    assert(stopped);
     stopped = false;
-    handle.startWatch(poller);
+    if (!queue.empty()) condition.set();
+    handle.rewatch();
+}
+
+template <class T> PollableQueue<T>::~PollableQueue() {
+    handle.stopWatch();
 }
 
 template <class T> void PollableQueue<T>::push(const T& t) {
     ScopedLock l(lock);
+    if (queue.empty()) condition.set();
     queue.push_back(t);
-    condition.set();
 }
 
 template <class T> void PollableQueue<T>::dispatch(sys::DispatchHandle& h) {
-    ScopedLock l(lock);
-    if (stopped) return;
-    dispatching = true;
-    condition.clear();
-    batch.clear();
-    batch.swap(queue);          // Snapshot of current queue contents.
-    {
-        // Process outside the lock to allow concurrent push.
-        ScopedUnlock u(lock);
-        callback(batch.begin(), batch.end()); 
+    ScopedLock l(lock);     // Prevent concurrent push
+    assert(dispatcher.id() == 0 || dispatcher.id() == Thread::current().id());
+    dispatcher = Thread::current();
+    while (!stopped && !queue.empty()) {
+        T value = queue.front();
+        queue.pop_front();
+        {   // callback outside the lock to allow concurrent push.
+            ScopedUnlock u(lock);
+            callback(value);
+        }
     }
-    batch.clear();
-    dispatching = false;
+    if (queue.empty()) condition.clear();
     if (stopped) lock.notifyAll();
-    else h.rewatch();
+    dispatcher = Thread();
+    if (!stopped) h.rewatch();
 }
 
 template <class T> void PollableQueue<T>::stop() {
     ScopedLock l(lock);
-    handle.stopWatch();
+    assert(!stopped);
+    handle.unwatch();
     stopped = true;
-    while (dispatching) lock.wait();
-}
-
-template <class T> bool PollableQueue<T>::isStopped() const {
-   ScopedLock l(lock);
-   return stopped;
+    // No deadlock if stop is called from the dispatcher thread
+    while (dispatcher.id() && dispatcher.id() != Thread::current().id())
+        lock.wait();
 }
 
 }} // namespace qpid::sys
-- 
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