On Mon, 2009-02-09 at 04:10 -0800, Ingo Molnar wrote:

> 
> Applied to tip:x86/urgent, thanks guys!

Thanks Ingo, 

I gave the tip tree a spin today and hit this bug.

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<(null)>] (null)
*pdpt = 0000000000839001 *pde = 0000000000c97067 *pte = 0000000000000163
Oops: 0000 [#1] SMP
last sysfs file:
Modules linked in:

Pid: 1, comm: swapper Not tainted (2.6.29-rc4-tip #18) VMware Virtual
Platform
EIP: 0062:[<00000000>] EFLAGS: 00010293 CPU: 0
EIP is at 0x0
EAX: 00000001 EBX: 00006000 ECX: c077ed00 EDX: 00006000
ESI: 00000001 EDI: 00000001 EBP: ef04cf40 ESP: ef04cf1c
 DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 006a
Process swapper (pid: 1, ti=ef04c000 task=ef050000 task.ti=ef04c000)
Stack:
 c0644e52 00000000 ef04cf24 ef04cf24 c064468d c0886dc0 00000000 c0702aea
 ef055480 00000001 00000101 dead4ead ffffffff ffffffff c08af530 00000000
 c0709715 ef04cf60 ef04cf60 00000001 00000000 00000000 dead4ead ffffffff
Call Trace:
 [<c0644e52>] ? native_cpu_up+0x2de/0x45b
 [<c064468d>] ? do_fork_idle+0x0/0x19
 [<c0645c5e>] ? _cpu_up+0x88/0xe8
 [<c0645d20>] ? cpu_up+0x42/0x4e
 [<c07e7462>] ? kernel_init+0x99/0x14b
 [<c07e73c9>] ? kernel_init+0x0/0x14b
 [<c040375f>] ? kernel_thread_helper+0x7/0x10
Code:  Bad EIP value.
EIP: [<00000000>] 0x0 SS:ESP 006a:ef04cf1c


This happens with out the fix too. So was wondering if there is any
other known bug in the tip tree. 
Also note that i synced to the mainline tree (29-rc4) and that works
fine. So this only exists in tip.
I will debug this later today, but if anyone has any ideas about this
bug do let me know. 

And ya i also had to apply this patch to get tip to compile. 
--
commit 22142120d931329efa53920739c74e7043bb2cb2
Author: Tejun Heo <tj@kernel.org>
Date:   Mon Feb 9 22:17:39 2009 +0900

    x86: fix math_emu register frame access

introduced the build error i assume.

Index: linux-tip-master/arch/x86/kernel/traps.c
===================================================================
--- linux-tip-master.orig/arch/x86/kernel/traps.c	2009-02-09 10:00:56.000000000 -0800
+++ linux-tip-master/arch/x86/kernel/traps.c	2009-02-09 10:11:29.000000000 -0800
@@ -900,7 +900,7 @@
 EXPORT_SYMBOL_GPL(math_state_restore);
 
 #ifndef CONFIG_MATH_EMULATION
-void math_emulate(struct math_emu_info *info)
+asmlinkage void math_emulate(struct math_emu_info *info)
 {
 	printk(KERN_EMERG
 		"math-emulation not enabled and no coprocessor found.\n");