Kernel 'bisection'

Bob ubuntu-qygzanxc at listemail.net
Sat Feb 14 23:40:34 UTC 2015


** Reply to message from Chris <cpollock at embarqmail.com> on Sat, 14 Feb 2015
16:20:25 -0600

> On Sat, 2015-02-14 at 13:42 -0500, Scott Blair wrote:
> > On 02/14/2015 08:19 AM, Chris wrote:
> > > On Sat, 2015-02-14 at 13:05 +0000, Peter Waller wrote:
> > >> Briefly, bisection is a way of taking a long list of 1000's of
> > >> changes, and arranging things so that you only have to test more like
> > >> 10 of them, because you test midpoints. (and 2^10 ~ 1000).
> > >>
> > >>
> > >> More detail:
> > >>
> > >>
> > >> http://alblue.bandlem.com/2011/07/git-tip-of-week-git-bisect.html
> > >>
> > >>
> > >> On 14 February 2015 at 12:57, Liam Proven <lproven at gmail.com> wrote:
> > >>          On 14 February 2015 at 02:59, Chris <cpollock at embarqmail.com>
> > >>          wrote:
> > >>          > Who can give me some pointers on doing a kernel bisection on
> > >>          either
> > >>          > 3.13.0-35 or -36 kernels? Ever since one of those two were
> > >>          installed,
> > >>          > I'm on -45 now, my system will lockup (black screen, cursor
> > >>          moves, but
> > >>          > CTRL-ALT-F1 will not take me to a terminal log-in. This is
> > >>          the error I
> > >>          > see - Feb 13 19:05:22 localhost kernel: [807775.808019]
> > >>          > [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer
> > >>          elapsed... render
> > >>          > ring idle. I've reported this last year on Launchpad as bug
> > >>          -
> > >>          > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1402331
> > >>          I've jumped
> > >>          > through all the hoops that have been suggested there except
> > >>          doing a
> > >>          > kernel bisection which seems to have me confused. I'm really
> > >>          getting a
> > >>          > bit tired of these continued 'lockups'.
> > >>          
> > >>          
> > >>          I have to ask. WTF is a "kernel bisection"?
> > >>          
> > >>          You want to... cut your kernel in half? Is this some kind of
> > >>          Solomonic
> > >>          judgement? Because, you know, like half a baby doesn't work,
> > >>          half a
> > >>          kernel won't, either.
> > >>          
> > > That, to me, is as clear as mud just as these instructions on doing it
> > > are - https://wiki.ubuntu.com/Kernel/KernelBisection I can't live with
> > > having these 'lockups' every 2-10 days, more or less and I say that
> > > because it's so very random I have no idea what even triggers it.
> > >
> > >
> > Chris, I just had a lock up about 3 minutes go. I saw that my memory sky 
> > rocketed, physical 99% and swap 90%. Normally they run low. CPU was 
> > running normal when it happened. I was logging into a flash page when it 
> > happened. The flash page finally crashed and everything went back to 
> > normal. I am using Ubuntu 14. 04 kernel 3.13.0-45-generic and Chrome 
> > 40.0.2214.111 64 bit. Don't know if this will help in your problem.
> > 
> > -- 
> > 
> > Scott Blair
> > 
> > Save on back up time BackupDevice=Null
> > 
> > 
> I've had flash crash a few times since the latest update. Did the system
> 'lockup'?

I have had my computer lockup twice the past few weeks.  I was not using a
browser the last time the lockup occurred and don't remember what I was doing
the first time it locked up.


> For instance I have my clock showing seconds when this happens
> to me the screen locks up however all background operations such as
> fetchmail, procmail, spamassassin and so forth continue to run.

These are the symptoms I also see.  There are no screen updates and the cursor
moves but the system will not accept any other input and anything already
running continues to run.


> If you
> didn't see that type of a lockup then it must have just been flash.
> However you can check your syslog for kernel: [ 8248.820016]
> [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... render
> ring idle to see if you have the same issue.

The last time I had the system lockup I left it running over night to see if
anything would happen.  After a reboot I looked in the logs and could not find
anything that happened at the time the lockup  occurred.  Checking my syslog I
can not find the string "hangcheck".


> 
> On another note I just tried to regress to the 3.13.0-35 kernel, system
> would boot but had no cursor and login screen didn't look right. Could
> not login so I removed it. 
> 
> So basically I'm back to where I was before just waiting for someone
> from either of the two bug reports to tell me what to do next and
> waiting for the next lockup.

-- 
Robert Blair



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