Re: [PATCH 1/2] nohz: Disable LOCKUP_DETECTOR when NO_HZ_FULL isenabled

From: Peter Zijlstra
Date: Thu May 16 2013 - 04:12:31 EST

On Wed, May 15, 2013 at 01:04:01PM -0400, Steven Rostedt wrote:
> On Wed, 2013-05-15 at 18:59 +0200, Peter Zijlstra wrote:
> > At which point we could run the watchdog without perf_event_task_tick().
> At which point we can drop the disable LOCKUP_DETECTOR when NO_HZ_FULL
> is enabled ;-)

Can we? The thing I'm worried about is RCU (of course!). ISTR we rely on RCU
working in NMI context. AFAIR for RCU to work, we need to come out of out magic
NO_HZ state since that would've put RCU into EQS.

Frederic, PaulMck?
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