Bug#538332: linux-2.6: [x86] Null pointer dereference in hrtick_start_fair.

[dann frazier <dannf@dannf.org>]

On Mon, Jul 27, 2009 at 10:32:44AM -0700, Alok Kataria wrote:
> 
> On Sat, 2009-07-25 at 10:24 -0700, dann frazier wrote:
> > On Fri, Jul 24, 2009 at 02:33:38PM -0700, Alok Kataria wrote:
> > > Package: linux-2.6
> > > Version: Debian 5.0r2
> > > 
> > > Hi,
> > > 
> > > There was a regression on mainline kernel due to my patches for tsc
> > > unification. 
> > > It seems lenny has picked-up those unification patches but didn't pick
> > > the fix for that regression. 
> > 
> > Thanks for the report.
> > Are you referring to the tsc_32/tsc_64 merge? We haven't included that
> > for lenny and there aren't currently any plans to.
> 
> Yep that is what I was referring to. Its strange that the bug I am
> seeing is so similar to the one reported in that commit. 
> Maybe something else is causing this panic it seems let me see if I can
> get to the bottom of it.

Cool, thanks for helping us here.

> >  The fixes for
> > #524542 that I have in the abi branch use the pre-merge version from
> > Ubuntu.
> 
> I see, though I must say that its really confusing for a person like me,
> I had assume that kernel version 2.6.26 will have all the stuff from the
> vanilla tree, but it seems you do things differently. 

We may still be talking about two different things. We are based upon
the vanilla 2.6.26 tree, but the tsc merging didn't appear to happen
unil 2.6.27-rc1.

Specifically, the tsc.c file was introduced here:

commit 0ef95533326a7b37d16025af9edc0c18e644b346
Author: Alok Kataria <akataria@vmware.com>
Date:   Tue Jul 1 11:43:18 2008 -0700

    x86: merge sched_clock handling
    
    Move the basic global variable definitions and sched_clock
    handling in the
    common "tsc.c" file.
    
     - Unify notsc kernel command line handling for 32 bit and 64bit.
     - Functional changes for 64bit.
            - "tsc_disabled" is updated if "notsc" is passed at
	    boottime.
            - Fallback to jiffies for sched_clock, incase notsc is
	    passed on
          commandline.
    
    Signed-off-by: Alok N Kataria <akataria@vmware.com>
    Signed-off-by: Dan Hecht <dhecht@vmware.com>
    Cc: Dan Hecht <dhecht@vmware.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

dannf@krebs:~/git/linux-2.6$ git name-rev 0ef95533326a7b37d16025af9edc0c18e644b346
0ef95533326a7b37d16025af9edc0c18e644b346 tags/v2.6.27-rc1~1102^2~72

  -dann