Re: [PATCH v2 6/8] kvm tools: Add rwlock wrapper

Ingo Molnar
2011-06-03T07:34:41Z

* Sasha Levin <levinsasha928@gmail.com> wrote:

> > with no apparent progress being made.
>
> Since it's something that worked in 2.6.37, I've looked into it to
> find what might have caused this issue.
>
> I've bisected guest kernels and found that the problem starts with:
>
> a26ac2455ffcf3be5c6ef92bc6df7182700f2114 is the first bad commit
> commit a26ac2455ffcf3be5c6ef92bc6df7182700f2114
> Author: Paul E. McKenney <paul.mckenney@linaro.org>
> Date: Wed Jan 12 14:10:23 2011 -0800
>
> rcu: move TREE_RCU from softirq to kthread
>
> Ingo, could you confirm that the problem goes away for you when you
> use an earlier commit?

testing will have to wait, but there's a recent upstream fix:

d72bce0e67e8: rcu: Cure load woes

That *might* perhaps address this problem too.

If not then this appears to be some sort of RCU related livelock with
brutally overcommitted vcpus. On native this would show up too, in a
less drastic form, as a spurious bootup delay.

Thanks,

Ingo