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:

quoted

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