Regression in RCU subsystem in latest mainline kernel

[Benjamin Herrenschmidt]

On Tue, 2013-06-25 at 17:19 +1000, Michael Ellerman wrote:
> Here's another trace from 3.10-rc7 plus a few local patches.
> 
> We suspect that the perf enable could be causing a flood of
> interrupts, but why
> that's clogging things up so badly who knows.

Additionally, perf being potentially NMIs , we might be hitting a bad
case of reentrance in RCU ... hard to tell.

Cheers,
Ben.