On Fri, 2018-12-14 at 13:04 +0000, Daniel P. Berrangé wrote:
The virtualization driver has two connections to the virtlogd
daemon,
one pipe fd for writing to the log file, and one socket fd for making
RPC calls. The typical sequence is to write some data to the pipe fd and
then make an RPC call to determine the current log file offset.
Unfortunately these two operations are not guaranteed to be handling in
order by virtlogd. The event loop for virtlogd may identify an incoming
event on both the pipe fd and socket fd in the same iteration of the
event loop. It is then entirely possible that it will process the socket
fd RPC call before reading the pending log data from the pipe fd.
As a result the virtualization driver will get an outdated log file
offset reported back.
This can be seen with the QEMU driver where, when a guest fails to
start, it will randomly include too much data in the error message it
has fetched from the log file.
It looks like this patch will address
https://bugzilla.redhat.com/show_bug.cgi?id=1356108
If that's indeed the case, you can consider adding the link to the
commit message before pushing.
--
Andrea Bolognani / Red Hat / Virtualization