问题
I'm using IOCP on UDP socket, and the UDP socket may be closed in another thread. So, how can I free Per Socket Context and Per I/O Context which associated with SOCKET safely?
When I close the socket, there will still be un-completed I/O request in kernel queue.
If I free context just when socket closed, the GetQueueCompletionStatus may failed.
Now, my question is when to free context?
回答1:
I use reference counting on all of my per socket and per I/O data structures. It makes this kind of thing easy as they are deleted when their references drop to 0. For some example code which shows one way to do this you could take a look at my free IOCP framework which you can download from here.
回答2:
Use a mutex to enforce mutual exclusion in a critical section of your code that will check the availability of the socket, and open it if necessary. Lock the socket to that thread, and release it appropriately when finished.
回答3:
I reuse my per-socket structures. After I have received completion events for all of the read and write operations that are required for that connection, I call TransmitFile with the TF_DISCONNECT and TF_REUSE_SOCKET flags to reset the socket without having to close it. I also reset the per-connection data once the completion event for the TransmitFile call comes through.
回答4:
Close the socket first. You will get error (I think it is ERROR_OPERATION_ABORTED) from GetQueuedCompletionStatus, and then it is right time to free the structure. There are no other uncompleted requests on this connection in kernel queue by then, completion packets are maintained in FIFO order, and error packet will definitely be the last one for this connection.
来源：https://stackoverflow.com/questions/677155/i-o-completion-port-how-to-free-per-socket-context-and-per-i-o-context