Re: [libvirt] [PATCH 3/7] Rewrite LXC I/O forwarding to use main event loop

From: "Daniel P. Berrange"<berrange(a)redhat.com> The current I/O code for LXC uses a hand crafted event loop to forward I/O between the container& host app, based on epoll to handle EOF on PTYs. This event loop is not easily extendable to add more consoles, or monitor other types of

file descriptors. Remove the custom event loop and replace it with a normal libvirt event loop. When detecting EOF on a PTY, disable the event watch on that FD, and fork off a background thread that does a edge-triggered epoll() on the FD. When the FD finally shows new incoming data, the thread re-enables the watch on the FD and exits. When getting EOF from a read() on the PTY, the existing code would do waitpid(WNOHANG) to see if the container had exited. Unfortunately there is a race condition, because even though the process has closed its stdio handles, it might still exist. To deal with this the new event loop uses a SIG_CHILD handler to perform the waitpid only when the container is known to have actually exited. * src/lxc/lxc_controller.c: Rewrite the event loop to use the standard APIs. --- cfg.mk | 2 +- src/lxc/lxc_controller.c | 607 ++++++++++++++++++++++++++++++---------------- 2 files changed, 404 insertions(+), 205 deletions(-)

+ +static void lxcConsoleEOFThread(void *opaque) +{ + struct lxcConsoleEOFData *data = opaque; + int ret; + int epollfd = -1; + struct epoll_event event; + + VIR_WARN("MOnitor %d", data->fd);

+ if ((epollfd = epoll_create(2))< 0) { + virReportSystemError(errno, "%s", + _("Unable to create epoll fd")); + goto cleanup; + }

+static void lxcConsoleIO(int watch, int fd, int events, void *opaque) +{

+ if (done> 0) + *len += done; + else { + VIR_WARN("Read fd %d done %d errno %d", fd, (int)done, errno); + }

+error: + virEventRemoveHandle(console->contWatch); + virEventRemoveHandle(console->hostWatch); + console->contWatch = console->hostWatch = -1; + quit = true; + virMutexUnlock(&lock);

+ if (virMutexInit(&lock)< 0) + goto cleanup2; + + if (pipe(sigpipe)< 0) {

+ if (virEventAddHandle(sigpipe[0], + VIR_EVENT_HANDLE_READABLE, + lxcSignalChildIO, +&container, + NULL)< 0) { + lxcError(VIR_ERR_INTERNAL_ERROR, "%s", + _("Unable to watch signal socket"));