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@veillard.com | Rpmfind RPM search engine http://rpmfind.net/ http://veillard.com/ | virtualization library http://libvirt.org/