Re: [libvirt] PATCH: 25/28: Thread safety for libvirtd event loop

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(); } }