[PATCH 3/3] iphlpapi: Implement CancelIPChangeNotify.

[Hans Leidekker]

On Tue, 2013-05-07 at 10:04 -0600, Erich E. Hoover wrote:
> On Tue, May 7, 2013 at 3:14 AM, Hans Leidekker <hans at codeweavers.com> wrote:
> > ...
> > TerminateThread is not the right tool here. If the thread is blocked on the
> > recv call while being terminated it will leak the netlink socket.
> >
> > You'd need a way to synchronize the threads, but an overhead of one thread per
> > caller is rather costly in the first place. This suggests that the server should
> > poll the socket.
> 
> So far the iphlpapi hasn't been doing anything directly with the
> server...  How about launching a single thread for NotifyAddrChange
> (when needed) and keeping a list of OVERLAPPED structures to signal

It's a system-wide event so the server seems to be a pretty good candidate
to handle it, and it wouldn't need any extra threads.

> when the list changes?  It's easy enough to use MSG_DONTWAIT to make
> recv non-blocking so that it's easy to cancel the thread.

You'd be consuming cpu instead of properly waiting. I guess you could make
this work if you poll an array with the netlink fd and another unix fd to
signal the cancel event, but again, I think this is best handled by the server.