From dd09443b0b3c0b5d1a8c034644d1065dd25bf5a9 Mon Sep 17 00:00:00 2001
From: Determinant <ted.sybil@gmail.com>
Date: Sun, 11 Nov 2018 23:02:59 -0500
Subject: start debugging multiloops design

---
 include/salticidae/event.h | 60 ++++++++++++++++++++++++----------------------
 1 file changed, 32 insertions(+), 28 deletions(-)

(limited to 'include/salticidae/event.h')

diff --git a/include/salticidae/event.h b/include/salticidae/event.h
index 857518b..ddb93fc 100644
--- a/include/salticidae/event.h
+++ b/include/salticidae/event.h
@@ -53,8 +53,8 @@ class EventContext: public _event_context_ot {
     EventContext(EventContext &&) = default;
     EventContext &operator=(const EventContext &) = default;
     EventContext &operator=(EventContext &&) = default;
-    void dispatch() { event_base_dispatch(get()); }
-    void stop()  { event_base_loopbreak(get()); }
+    void dispatch() const { event_base_dispatch(get()); }
+    void stop() const { event_base_loopbreak(get()); }
 };
 
 class Event {
@@ -122,7 +122,7 @@ class Event {
 };
 
 template<typename T>
-class MPSCQueueEventDriven: public MPMCQueue<T> {
+class MPSCQueueEventDriven: public MPSCQueue<T> {
     private:
     const uint64_t dummy = 1;
     std::atomic<bool> wait_sig;
@@ -130,38 +130,39 @@ class MPSCQueueEventDriven: public MPMCQueue<T> {
     Event ev;
 
     public:
-    template<typename Func>
-    MPSCQueueEventDriven(const EventContext &ec, Func &&func,
-                        size_t burst_size = 128, size_t capacity = 65536):
-        MPMCQueue<T>(capacity),
+    MPSCQueueEventDriven(size_t capacity = 65536):
+        MPSCQueue<T>(capacity),
         wait_sig(true),
-        fd(eventfd(0, EFD_NONBLOCK)),
-        ev(Event(ec, fd, EV_READ | EV_PERSIST,
-            [this, func=std::forward<Func>(func), burst_size](int, short) {
-            uint64_t t;
-            read(fd, &t, 8);
-            //fprintf(stderr, "%x\n", std::this_thread::get_id());
-            T elem;
-            size_t cnt = burst_size;
-            while (MPMCQueue<T>::try_dequeue(elem))
-            {
-                func(std::move(elem));
-                if (!--cnt)
-                {
-                    write(fd, &dummy, 8);
-                    return;
-                }
-            }
-            wait_sig.store(true, std::memory_order_relaxed);
-        })) { ev.add(); }
+        fd(eventfd(0, EFD_NONBLOCK)) {}
 
     ~MPSCQueueEventDriven() { close(fd); }
 
+    template<typename Func>
+    void reg_handler(const EventContext &ec, Func &&func) {
+        ev = Event(ec, fd, EV_READ | EV_PERSIST,
+                    [this, func=std::forward<Func>(func)](int, short) {
+                    //fprintf(stderr, "%x\n", std::this_thread::get_id());
+                    uint64_t t;
+                    read(fd, &t, 8);
+                    // the only undesirable case is there are some new items
+                    // enqueued before recovering wait_sig to true, so the consumer
+                    // won't be notified. In this case, no enqueuing thread will
+                    // get to write(fd). Then store(true) must happen after all exchange(false),
+                    // since all enqueue operations are finalized, the dequeue should be able
+                    // to see those enqueued values in func()
+                    wait_sig.store(true, std::memory_order_release);
+                    if (func(*this))
+                        write(fd, &dummy, 8);
+                });
+        ev.add();
+    }
+
     template<typename U>
     bool enqueue(U &&e) {
         static const uint64_t dummy = 1;
-        bool ret = MPMCQueue<T>::enqueue(std::forward<U>(e));
-        if (wait_sig.exchange(false, std::memory_order_relaxed))
+        bool ret = MPSCQueue<T>::enqueue(std::forward<U>(e));
+        // memory barrier here, so any load/store in enqueue must be finialized
+        if (wait_sig.exchange(false, std::memory_order_acq_rel))
         {
             SALTICIDAE_LOG_DEBUG("mpsc notify");
             write(fd, &dummy, 8);
@@ -170,6 +171,8 @@ class MPSCQueueEventDriven: public MPMCQueue<T> {
     }
 };
 
+// TODO: incorrect MPMCQueueEventDriven impl
+/*
 template<typename T>
 class MPMCQueueEventDriven: public MPMCQueue<T> {
     private:
@@ -223,6 +226,7 @@ class MPMCQueueEventDriven: public MPMCQueue<T> {
         return ret;
     }
 };
+*/
 
 }
 
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