linux-kernel - Re: [PATCH v2 1/4] nmi_backtrace: add more trigger_*_cpu

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Message-ID: <20160317231128.GB6344@twins.programming.kicks-ass.net>
Date:	Fri, 18 Mar 2016 00:11:28 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Chris Metcalf <cmetcalf@...lanox.com>,
	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Aaron Tomlin <atomlin@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Andrew Morton <akpm@...l.org>,
	Daniel Thompson <daniel.thompson@...aro.org>, x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace()
 methods

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.