[patch] i386-PDA, lockdep: fix %gs restore

[Ingo Molnar <mingo@elte.hu>]

Jeremy,

could you back out Andi's patch and try the patch below, does it fix the 
crash too?

	Ingo

--------------->
Subject: [patch] i386-PDA, lockdep: fix %gs restore
From: Ingo Molnar <mingo@elte.hu>

in the syscall exit path the %gs selector has to be restored _after_ the
last kernel function has been called. If lockdep is enabled then this
kernel function is TRACE_IRQS_ON.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
 arch/i386/kernel/entry.S |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux/arch/i386/kernel/entry.S
===================================================================
--- linux.orig/arch/i386/kernel/entry.S
+++ linux/arch/i386/kernel/entry.S
@@ -326,11 +326,12 @@ sysenter_past_esp:
 	testw $_TIF_ALLWORK_MASK, %cx
 	jne syscall_exit_work
 /* if something modifies registers it must also disable sysexit */
-1:	mov  PT_GS(%esp), %gs
+1:
+	TRACE_IRQS_ON
+	mov  PT_GS(%esp), %gs
 	movl PT_EIP(%esp), %edx
 	movl PT_OLDESP(%esp), %ecx
 	xorl %ebp,%ebp
-	TRACE_IRQS_ON
 	ENABLE_INTERRUPTS_SYSEXIT
 	CFI_ENDPROC
 .pushsection .fixup,"ax";	\
-
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