Re: [GIT PULL rcu/next] rcu commits for 2.6.40

From: Paul E. McKenney
Date: Sat May 14 2011 - 10:49:39 EST


On Fri, May 13, 2011 at 04:40:59PM +0200, Ingo Molnar wrote:
>
> * Ingo Molnar <mingo@xxxxxxx> wrote:
>
> > > very clearly indicate that this is an RCU regression.
> >
> > This might be the same one Yinghai found:
> >
> > e59fb3120bec: rcu: Decrease memory-barrier usage based on semi-formal proof
> >
> > So with the config i sent it's definitely reproducible.
>
> yes. And note that the system does not lock up, but boots up after a really
> long time - perhaps as a side-effect of very rare timer irqs driving forward
> the RCU state machine?

In the interest of focusing on the code paths that are actually being
executed...

Are you guys seeing NMIs at about the time the slowdown occurs?

Thanx, Paul
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