On Mon, Dec 01, 2008 at 12:18:24AM +0000, Daniel P. Berrange wrote:
> This patch makes the event loop in the libvirtd daemon thread safe, and
> re-entrant. This allows one thread to add/remove/update timers/file handle
> watches while other thread is doing the poll. This sometimes requires that
> we wakeup the main thread to make it see changes to the poll FD list. We
> use the traditional self-pipe trick for this task.
[...]
> -static int virEventDispatchHandles(struct pollfd *fds) {
> +static int virEventDispatchHandles(int nfds, struct pollfd *fds) {
> int i;
> - virEventHandleType hEvents;
> - /* Save this now - it may be changed during dispatch */
> - int nhandles = eventLoop.handlesCount;
>
> - for (i = 0 ; i < nhandles ; i++) {
> + for (i = 0 ; i < nfds ; i++) {
> if (eventLoop.handles[i].deleted) {
> EVENT_DEBUG("Skip deleted %d", eventLoop.handles[i].fd);
> continue;
> }
>
> if (fds[i].revents) {
> - hEvents = virPollEventToEventHandleType(fds[i].revents);
> - EVENT_DEBUG("Dispatch %d %d %d %p",
> - eventLoop.handles[i].watch,
> - fds[i].fd, fds[i].revents,
> - eventLoop.handles[i].opaque);
> - (eventLoop.handles[i].cb)(eventLoop.handles[i].watch,
> - fds[i].fd,
> - hEvents,
> - eventLoop.handles[i].opaque);
> + virEventHandleCallback cb = eventLoop.handles[i].cb;
> + void *opaque = eventLoop.handles[i].opaque;
> + int hEvents = virPollEventToEventHandleType(fds[i].revents);
> + EVENT_DEBUG("Dispatch %d %d %p", fds[i].fd,
> + fds[i].revents, eventLoop.handles[i].opaque);
> + virEventUnlock();
> + (cb)(eventLoop.handles[i].watch,
> + fds[i].fd, hEvents, opaque);
> + virEventLock();
> }
> }
Hum, if this routine assume we enter it with the event lock and keep
it though its lifetime except when dispatching, then I guess it's worth
a comment, right ? Is there only one thread which can access or
unregister fds, or do we have another lock in place ?
Looks okay, but it's far from trivial,
Daniel
--
Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
daniel@xxxxxxxxxxxx | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library http://libvirt.org/
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