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Subject: Re: Oops in trace_hardirqs_on (powerpc)
From: Steven Rostedt <rostedt@goodmis.org>
To: =?ISO-8859-1?Q?J=F6rg?= Sommer <joerg@alea.gnuu.de>
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Date: Wed, 22 Dec 2010 21:42:56 -0500
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On Sun, 2010-12-19 at 14:27 +0100, Jörg Sommer wrote:
> Hi Steven,
> 

> Did you've fixed this problem? The bug report is still marked as open.
> https://bugzilla.kernel.org/show_bug.cgi?id=16573
> 

I just posted a patch to that BZ. I have it here below too. Could you
see if it fixes you problem. I only fixed the one place that you
reported, it may need more fixes (and in that case a macro to do the
work).

I hit the same bug on my ppc64 box, and have a fix for that, that I'll
post to LKML tomorrow.

-- Steve

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index ed4aeb9..915cc03 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -879,7 +879,18 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_47x)
 	 */
 	andi.	r10,r9,MSR_EE
 	beq	1f
+	/*
+	 * Since the ftrace irqsoff latency trace checks CALLER_ADDR1,
+	 * which is the stack frame here, we need to force a stack frame
+	 * in case we came from user space.
+	 */
+	stwu	r1,-32(r1)
+	mflr	r0
+	stw	r0,4(r1)
+	stwu	r1,-32(r1)
 	bl	trace_hardirqs_on
+	lwz	r1,0(r1)
+	lwz	r1,0(r1)
 	lwz	r9,_MSR(r1)
 1:
 #endif /* CONFIG_TRACE_IRQFLAGS */