Kernel 'bisection'

NoOp glgxg at sbcglobal.net
Sun Feb 15 21:46:14 UTC 2015


On 02/14/2015 03:40 PM, Bob wrote:
> ** 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".

You might want to have a look at:

<https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1384342>
(kernel messages intel_crtc_wait_for_pending_flips correlate to compiz hang)

I had one of these just last night (my commenta are in #60 & #61)



> 
> 
>> 
>> 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.
> 





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