On Thu, 18 Jun 2015, Alexander Vasiliev wrote:
> I have installed ipvsadm (1.2.1) on Linux Ubuntu-14.04 (3.13.0-55-generic)
> Next I create service: ipvsadm -A -t 172.16.0.12:http -s lblc.
> When I tried edit created service I got kernel panic. Edit command: ipvsadm
> -A -t 172.16.0.12:http -s rr, for example.
> The problem is repeatable, I try in VirtualBox.
You mean second command is -E, not -A, right?
It looks like I completely messed the scheduler editing
with commit ceec4c381681 ("ipvs: convert services to rcu").
The problem is with the svc->sched_data. I forgot about it.
The reverse order of ip_vs_bind_scheduler and
ip_vs_unbind_scheduler causes problem in all cases
for schedulers that maintain sched_data.
And RCU readers are not guaranteed to get the
scheduler+sched_data pointers safely for same scheduler.
The simple fix would be to make sure
ip_vs_unbind_scheduler and ip_vs_bind_scheduler work
in this order but with synchronize_rcu between them.
Something like what was before this change.
The individual schedulers will not be touched.
As changing of scheduler is a rare operation it can
be the initial bugfix. If we want to fix it without
such delay we have to change all schedulers, may be
by moving sched_data in some new struct scheduler_context
where schedulers can store their sched_data. Then
svc->sched_context (RCU ptr) can contain both the
scheduler and the sched_data pointers.
Julian Anastasov <ja@xxxxxx>
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