Re: [libvirt] [PATCH] Fix deadlock in QEMU close callback APIs

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; There is a lock ordering problem in the QEMU close callback APIs. When starting a guest we have a lock on the VM. We then set a autodestroy callback, which acquires a lock on the close callbacks. When running auto-destroy, we obtain a lock on the close callbacks, then run each callbacks - which obtains a lock on the VM. This causes deadlock if anyone tries to start a VM, while autodestroy is taking place. The fix is to do autodestroy in 2 phases. First obtain all the callbacks and remove them from the list under the close callback lock. Then invoke each callback from outside the close callback lock. Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- src/qemu/qemu_conf.c | 106 ++++++++++++++++++++++++++++++++++++++++++-------- src/util/virnetlink.c | 5 ++- 2 files changed, 92 insertions(+), 19 deletions(-)

diff --git a/src/util/virnetlink.c b/src/util/virnetlink.c index 0b36fdc..8b47ede 100644 --- a/src/util/virnetlink.c +++ b/src/util/virnetlink.c @@ -335,8 +335,9 @@ virNetlinkEventCallback(int watch, if (length == 0) return; if (length < 0) { - virReportSystemError(errno, - "%s", _("nl_recv returned with error")); + virReportError(VIR_ERR_INTERNAL_ERROR, + _("nl_recv returned with error: %s"), + nl_geterror(length)); return; }