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Currently the LXC controller attempts to deal with EOF on a tty by spawning a thread to do an edge triggered epoll_wait(). This avoids the normal event loop spinning on POLLHUP. There is a subtle mistake though - even after seeing POLLHUP on a master PTY, it is still perfectly possible & valid to write data to the PTY. There is a buffer that can be filled with data, even when no client is present. The second mistake is that the epoll_wait() thread was not looking for the EPOLLOUT condition, so when a new client connects to the LXC console, it had to explicitly send a character before any queued output would appear. Finally, there was in fact no need to spawn a new thread to deal with epoll_wait(). The epoll file descriptor itself can be poll()'d on normally. This patch attempts to deal with all these problems. - The blocking epoll_wait() thread is replaced by a poll on the epoll file descriptor which then does a non-blocking epoll_wait() to handle events - Even if POLLHUP is seen, we continue trying to write any pending output until getting EAGAIN from write. - Once write returns EAGAIN, we modify the epoll event mask to also look for EPOLLOUT * src/lxc/lxc_controller.c: Avoid stalled I/O upon connected to an LXC console
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>