Re: [PATCH v2 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods

From: Paul E. McKenney
Date: Thu Mar 17 2016 - 20:37:06 EST

On Fri, Mar 18, 2016 at 12:11:28AM +0100, Peter Zijlstra wrote:
> On Thu, Mar 17, 2016 at 03:55:57PM -0700, Paul E. McKenney wrote:
> > The RCU stall-warn stack traces can be ugly, agreed.
> Ugly isn't the problem, completely random bollocks that puts you on the
> wrong path was more the problem.
> It uses a stack pointer saved at some random time in the past to start
> unwinding an active stack from. Completely and utter misery.

Yep, its accuracy does depend on what is going on, which was also my
experience with the NMI-based approach's reliablity.

Perhaps a boot-time parameter enabling the sysadm to pick the desired
flavor of poison?

Thanx, Paul