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

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Date:	Wed, 20 Aug 2008 07:46:44 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	Eran Liberty <liberty@...ricom.com>,
	Steven Rostedt <srostedt@...hat.com>,
	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linuxppc-dev@...abs.org, rostedt@...dmis.org
Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)


> Register GPR30 is always zero... (also true for the other oops)

>>From my experiments, -a- non volatile register gets corrupted. Not
always the same and not always with the same value.

The corruption -seems- to happen due to corruption of the location on
the stack where it was saved to / restored from in a previous function
call or interrupt.

I haven't yet tracked down what actually whacks the stack.

Ben.


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