[Libevent-users] Disabling callbacks and closing - block until callbacks finished

[nick@xxxxxxxx]

Situation:
----------

I am building a multithreaded socket server built with Libevent.   The  
event loop is run in its own thread and each callback creates a task  
into a queue.   A pool of worker threads then processes the tasks, (of  
course ensuring that tasks for any given connection are processed in  
the correct order).

When a close event arrives, a task is created to close the connection  
and free all related structures.   When this task is processed by a  
worker thread, it does the following things:

1. Disable all callbacks
2. Close the connection
3. Remove all pending tasks in the task queue for this connection

Problem:
--------

The problem is that after the connection is closed, there could still  
be events in the Libevent event loop either waiting to be processed in  
a callback or actually being processed by the event thread (i.e.  
callback running).   This could lead to tasks being created for the  
connection _after_ step 3 which would result in tasks in the task  
queue for a closed connection - which I want to avoid.

Solution?
---------

I could use a mutex to lock the connection in the event callbacks, but  
I do not want to introduce blocking methods in the event loop thread.

I could ensure that a connection is valid when I take a task.

But ideally I would like to the bufferevent close method, or the  
callback disable methods to block until all curently running callbacks  
for that bufferevent have finished.   This way I could be sure that no  
tasks can be created after the connection is closed.

Question:
---------

Do the methods work like this, or is there a way to achieve this?

Many thanks in advance.

Nick.


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