From: Dan Streetman <ddstr...@canonical.com> Buglink: https://launchpad.net/bugs/1823458
This is a race condition between the normal shutdown of a guest and the handling of its vhost-user net being externally closed. It's explained in more detail at the bug link; the short version is that there are 2 problems, fixed by the 2 patches. The first patch fixes the race condition where multiple threads call vhost_net_stop(), and the second patch prevents vhost-user from calling vhost_net_cleanup() on CHR_EVENT_CLOSED, because it will be cleaned up later and its fields will be accessed when vhost_net_stop() is called later. As explained in the bug report, this requires a rather complicated setup to reproduce, and I'm not able to create a setup to reproduce it myself. However this has been reported to me/Canonical, and the reporter is able to reproduce it consistently, so I've used them for debug and testing. This reproduction was done with the older 2.5 qemu, from Ubuntu Xenial; but the problem does still appear to exist in upstream qemu, based on review of the code, which is why I'm sending these patches. Dan Streetman (2): add VirtIONet vhost_stopped flag to prevent multiple stops do not call vhost_net_cleanup() on running net from char user event hw/net/virtio-net.c | 3 ++- include/hw/virtio/virtio-net.h | 1 + net/vhost-user.c | 1 - 3 files changed, 3 insertions(+), 2 deletions(-) -- 2.20.1
