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

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Message-Id: <1219268189.21386.65.camel@pasglop>
Date:	Thu, 21 Aug 2008 07:36:29 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Steven Rostedt <srostedt@...hat.com>,
	Scott Wood <scottwood@...escale.com>,
	Eran Liberty <liberty@...ricom.com>,
	Alan Modra <amodra@....ibm.com>,
	Segher Boessenkool <segher@...nel.crashing.org>
Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)


> > As you can see, it restores r1 -before- it pops r24..r31 off
> > the stack ! I let you imagine what happens if an interrupt happens
> > just in between those two instructions (mr and lmw). We don't do
> > redzones on our ABI, so basically, the registers end up corrupted
> > by the interrupt.
> 
> Ouch!  You've disassembled this without -pg too, and it does not have this 
> bug? What version of gcc do you have?

Oops, should have mentioned it ;-)

4.2.3 (Ubuntu 4.2.3-2ubuntu7)

Ben.


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