Bug 11951

Summary: Early boot failure for 2.6.28-rc[123]: NULL pointer deref stemming from scheduler_tick
Product: Timers Reporter: Theodore Tso (tytso)
Component: OtherAssignee: Thomas Gleixner (tglx)
Severity: normal CC: rjw
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: 2.6.28-rc2 Tree: Mainline
Subsystem: Regression: Yes
Bug Depends on:    
Bug Blocks: 11808    
Attachments: Bisection log
Boot log from a successful boot of 2.6.27 kernel
Kernel config file from a failing kernel during the bisection
The cpuinfo file from my system
/proc/timer_list from my 2.6.27 kernel

Description Theodore Tso 2008-11-04 14:39:08 UTC
Latest working kernel version: 2.6.27
Earliest failing kernel version: 2.6.28-rc1
Distribution: Ubuntu Hardy
Hardware Environment: Dual Processor Pentium 4 Xeon Whitebox
Software Environment:
Problem Description: oops in early boot

My fileserver boots under 2.6.27, but it is failing to boot on
2.6.28-rc2.  It took me a while to bisect, so after I finished the
bisection, I retested with the latest mainline
(v2.6.28-rc3-54-g75fa677), and the problem still shows up.

Essentially, the system panics in early boot, resulting in multiple
oops.  I finally was able get the very first oops, and the image of
that oops can be found here:


From the console snapshot, it looks like two CPU simultaneously
OOPS'ed with a:

BUG: unable to handle kernel NULL dereference at 00000000
BUG: unable to handle kernel NULL dereference at 00000038

On the stack is "scheduler_tick+0x83/0x15f"

When doing a bisection, the last good commit (i.e., the last one which
I can boot on my system) is git id: d6c88a50 (which preceeds 2.6.28-rc1).

The first bad git ID is:

commit d6c88a507ef0b6afdb013cba4e7804ba7324d99a
Author: Thomas Gleixner <tglx@linutronix.de>
Date:   Wed Oct 15 15:27:23 2008 +0200

    genirq: revert dynarray

    Revert the dynarray changes. They need more thought and polishing.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

... but in fact, the failure is different from the above messages.
The failure is once again in early boot, but the oops message is quite


The failure was in kmem_cache_alloc+0xab/0xc4, called by

Walking forwards, the first git ID which shows the same failure as
what shows up in 2.6.28-rc2 and 2.6.28-rc3 is git ID: 92b29b8, which
apparently is a merge of the tracing-v28-for-linus branch.  Because
there were two failures back-to-back, it's possible either I or git
bisect got confused, since normally the bisect normally doesn't
terminate on a merge commit.  I'll try double-checking the two
ancestors of the merge commit by hand, but in the meantime I thought
I'd send what I have in case it rings a bell.

Again, my system is totally failing to boot since 2.6.28-rc1.  This is
a Aberdeen (white box) fileserver, with a SuperMicro X6DH8-XG2
motherboard, with two Pentium 4 Xeon 3.0GHz with hyperthreading.
Comment 1 Theodore Tso 2008-11-04 14:40:08 UTC
Created attachment 18664 [details]
Bisection log
Comment 2 Theodore Tso 2008-11-04 14:40:42 UTC
Created attachment 18665 [details]
Boot log from a successful boot of 2.6.27 kernel
Comment 3 Theodore Tso 2008-11-04 14:41:25 UTC
Created attachment 18666 [details]
Kernel config file from a failing kernel during the bisection
Comment 4 Theodore Tso 2008-11-04 14:41:54 UTC
Created attachment 18667 [details]
The cpuinfo file from my system
Comment 5 Theodore Tso 2008-11-04 14:42:15 UTC
Created attachment 18668 [details]
/proc/timer_list from my 2.6.27 kernel
Comment 6 Theodore Tso 2008-11-04 15:11:22 UTC
Note: The LKML thread discussing this bug can be found here:

Comment 7 Rafael J. Wysocki 2008-11-08 15:25:46 UTC
References : http://lkml.org/lkml/2008/11/4/450
Comment 8 Rafael J. Wysocki 2008-11-08 15:28:01 UTC
Handled-By : Yinghai Lu <yinghai@kernel.org>
Patch : http://lkml.org/lkml/2008/11/4/431
Patch : http://lkml.org/lkml/2008/11/5/81