linux-kernel - Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)

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Message-Id: <1219110692.8062.0.camel@pasglop>
Date:	Tue, 19 Aug 2008 11:51:32 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Steven Rostedt <srostedt@...hat.com>
Cc:	Eran Liberty <liberty@...ricom.com>, linuxppc-dev@...abs.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	linux-kernel@...r.kernel.org, rostedt@...dmis.org
Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)

On Mon, 2008-08-18 at 11:07 -0400, Steven Rostedt wrote:
> Eran Liberty wrote:
> > After compiling a kernel with ftrace I started to experience all sorts 
> > of crashes.
> 
> Just to make sure...
> 
> ftrace enables markers too, and RCU has tracing with the markers. This 
> may not be the problem, but I just want to eliminate as many variables 
> as possible.
> Could you disable ftrace, but keep the markers on too.  Also, could you 
> enable ftrace again and turn on the FTRACE_STARTUP_TEST.

I spent some time last week tracking one of those crashes and it appears
that we are getting corruption of some of the non-volatile registers.

So far, I found out that it -seems- to be coming from stack frame
corruption during a timer interrupt.

I haven't had a chance to dig further yet.

Cheers,
Ben.


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