manager: fix event loop implementation

Event loop duplicate event handler map before looping on it.
So unregister an handler is not sync in this copy and
can call dead stuff.
Notice also registerEventHandler really replace the previous registered
handler as it's expected.

Refs #65401

Change-Id: Id2c27dd8ca42ee2a29fa3237bb836385deec11cd

daemon/src/managerimpl.cpp

@@ -1351,27 +1351,41 @@ ManagerImpl::removeStream(Call& call)
     getRingBufferPool().unBindAll(call_id);
 }
 
+// Not thread-safe, SHOULD be called in same thread that run poolEvents()
 void
 ManagerImpl::registerEventHandler(uintptr_t handlerId, EventHandler handler)
 {
-    eventHandlerMap_.insert(std::make_pair(handlerId, handler));
+    eventHandlerMap_[handlerId] = handler;
 }
 
+// Not thread-safe, SHOULD be called in same thread that run poolEvents()
 void
 ManagerImpl::unregisterEventHandler(uintptr_t handlerId)
 {
-    eventHandlerMap_.erase(handlerId);
+    auto iter = eventHandlerMap_.find(handlerId);
+    if (iter != eventHandlerMap_.end()) {
+        if (iter == nextEventHandler_)
+            nextEventHandler_ = eventHandlerMap_.erase(iter);
+        else
+            eventHandlerMap_.erase(iter);
+    }
 }
 
 // Must be invoked periodically by a timer from the main event loop
 void ManagerImpl::pollEvents()
 {
-    // Make a copy of handlers map as handlers can modify this map
-    const auto handlers = eventHandlerMap_;
-    for (const auto& it : handlers) {
+    auto iter = eventHandlerMap_.begin();
+    while (iter != eventHandlerMap_.end()) {
         if (finished_)
             return;
-        it.second();
+
+        // WARN: following callback can do anything and typically
+        // calls (un)registerEventHandler.
+        // Think twice before modify this code.
+
+        nextEventHandler_ = std::next(iter);
+        iter->second();
+        iter = nextEventHandler_;
     }
 }
 

daemon/src/managerimpl.h

@@ -968,7 +968,8 @@ class ManagerImpl {
     private:
         NON_COPYABLE(ManagerImpl);
 
-        std::map<uintptr_t, EventHandler> eventHandlerMap_{};
+        std::map<uintptr_t, EventHandler> eventHandlerMap_;
+        decltype(eventHandlerMap_)::iterator nextEventHandler_;
 
         /**
          * Test if call is a valid call, i.e. have been created and stored in