Re: [libvirt] [PATCH v5 3/3] libvirtd: fix crash on termination
[...]
>
> Patch looks good to me too. But still original "libvirtd: fix crash on
termination"
> fixes another issue and if applied fixes "virt-manager issue" as well as
John
> figured out.
Not sure there's enough coffee in the house this morning to make me
"awake enough" for all this stuff, especially just before a holiday
break. But perhaps better now than after the new year... sooo....
Finally I'm back on track with this (sorry for it taking so long), although
you're right about this, it's not the correct fix, it's just a byproduct of
your patch, however, the whole thing about closing connections and releasing
memory is a bit of a mess. For example, right now, we only dispose of service
objs (but we don't close them, we do that in virNetServerClose), but we both
close and dispose of the client objs. Another thing, we toggle the service to
stop accepting any new connections, but that's irrelevant at that point because
we've closed them already by that time as a product of calling
virNetDaemonClose->virNetServerClose->virNetServerServiceClose - so that
virNetServerServiceClose could call virNetServerServiceToggle(,false),
even though it probably doesn't matter at this point.
Makes me wonder why virNetServerUpdateServicesLocked wasn't called in
virNetServerDispose instead of open coding the nservices loop (sigh).
should be removed...I drifted a bit here, anyway, we need to make a
clear
distinction when we're releasing memory and when we're shutting down some kind
of service - sometimes both can be done at the same time (see below), however
it's very clear we can't do it here. Your issue is that Close currently only
closes the sockets (this reflects my point of "shutting down a service") but
does nothing with the threadpool connected to the server, thus leaving the
worker threads to continue running and executing APIs the results of which they
shouldn't even be able to return back to the client, since we're shutting down.
Now the thing with threadpool is that both memory release and teardown are
merged into one "object disposal" operation and therefore done as part of
virNetServerDispose. Since I understand a removal from the hash table as a
memory release operation, we should not be calling virHashRemoveAll from
virNetDaemonClose. Now, I see 2 options:
1) split virThreadPoolFree into 2 functions, one which only broadcasts the
"die" message and joins the threads (or waits for them in this case...) and
the
other releasing the resources - can't say I'm a fan of this one
Kind of a "virThreadPoolStop" type operation...
2) call virThreadPoolFree from virNetServerClose instead...
None of those approaches is ideal, but I can't seem to think off anything
better at the moment.
I like 2 better, but it doesn't fix the problem of a long running thread
(such as GetAllDomainStats), it just moves the cheese. Although I have
a feeling the virStateShutdown series Nikolay is promoting may solve
that issue.
It's really a conundrum w/r/t how much time to spend on this especially
if the short/long term goal is a shims for libvirtd (e.g. libvirt_qemu)
which will move the cheese even more.
I'm going to move away from this for now, maybe a fresh look will help.
Right now I'm not sure I can focus on this with the other threads I'm
involved in.
John
I'm open to discuss any other suggestions.
Erik
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