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

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Date:	Mon, 18 Aug 2008 14:47:32 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Scott Wood <scottwood@...escale.com>
cc:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Steven Rostedt <srostedt@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Eran Liberty <liberty@...ricom.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org
Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)


On Mon, 18 Aug 2008, Scott Wood wrote:

> Mathieu Desnoyers wrote:
> >         asm volatile (
> >                 "1: lwz         %1, 0(%2)\n"
> >                 "   cmpw        %1, %5\n"
> >                 "   bne         2f\n"
> >                 "   stwu        %3, 0(%2)\n"
> >                 "2:\n"
> >                 ".section .fixup, \"ax\"\n"
> >                 "3:     li %0, 1\n"
> >                 "       b 2b\n"
> >                 ".previous\n"
> >                 ".section __ex_table,\"a\"\n"
> >                 _ASM_ALIGN "\n"
> >                 _ASM_PTR "1b, 3b\n"
> >                 ".previous"
> >                 : "=r"(faulted), "=r"(replaced)
> >                 : "r"(ip), "r"(new),
> >                   "0"(faulted), "r"(old)
> >                 : "memory");
> 
> Some (most likely unrelated) nits in the above inline asm:
> 
> Should use a "b" constraint for %2, or you could get r0.  Or, use an "m"
> constraint with %U2%X2 after the lwz/stw. 

What syntax to do that with?

  lwz %1,0(%U2)
  stu %3, 0(%X2)

I'm new to those. (and the above does not compile)

> Why stwu with an offset of zero,

How else to do it?  stwu %3, (%2) does not compile for me.

-- Steve

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