[uml-devel] 2.6.18-skas-v9-pre9 broken

[uml-devel] 2.6.18-skas-v9-pre9 broken

[Christopher S. Aker]

Blaisorblade,

I recently deployed a 2.6.18-skas3-v9-pre9 host, and some users weren't 
able to boot UML beyond "VFS: Mounted root (ext3 filesystem) readonly". 
  As it turns out, only 2.6-um kernels were affected, 2.4-um worked fine.

This happened both in skas3 and skas0 modes.  Jeff graciously took a 
look at some straces, and his comment was that "something broke page 
fault handling generically".

The traces are here:

http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace.txt (skas3)
http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace_skas0.txt

Reverting back to a skas3-v8.2 kernel fixed it.

HTH,
-Chris


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Re: [uml-devel] 2.6.18-skas-v9-pre9 broken

[Blaisorblade]

On Thursday 05 October 2006 23:59, Christopher S. Aker wrote:
> Blaisorblade,
>
> I recently deployed a 2.6.18-skas3-v9-pre9 host, and some users weren't
> able to boot UML beyond "VFS: Mounted root (ext3 filesystem) readonly".
>   As it turns out, only 2.6-um kernels were affected, 2.4-um worked fine.
>
> This happened both in skas3 and skas0 modes.  Jeff graciously took a
> look at some straces, and his comment was that "something broke page
> fault handling generically".
>
> The traces are here:
>
> http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace.txt (skas3)
> http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace_skas0.txt
>
> Reverting back to a skas3-v8.2 kernel fixed it.
An important question: did the patch contain fremap code (the one for 
2.6.18-rc4 did)? That code does do heavy changes to page fault handling.
I'm also guessing this is a 32bit host.
-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade
Chiacchiera con i tuoi amici in tempo reale! 
 http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com 


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Re: [uml-devel] 2.6.18-skas-v9-pre9 broken

[Christopher S. Aker]

Blaisorblade wrote:
> On Thursday 05 October 2006 23:59, Christopher S. Aker wrote:
>> Blaisorblade,
>>
>> I recently deployed a 2.6.18-skas3-v9-pre9 host, and some users weren't
>> able to boot UML beyond "VFS: Mounted root (ext3 filesystem) readonly".
>>   As it turns out, only 2.6-um kernels were affected, 2.4-um worked fine.
>>
>> This happened both in skas3 and skas0 modes.  Jeff graciously took a
>> look at some straces, and his comment was that "something broke page
>> fault handling generically".
>>
>> The traces are here:
>>
>> http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace.txt (skas3)
>> http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace_skas0.txt
>>
>> Reverting back to a skas3-v8.2 kernel fixed it.
> An important question: did the patch contain fremap code (the one for 
> 2.6.18-rc4 did)? That code does do heavy changes to page fault handling.

No, it was not the fremap version.

> I'm also guessing this is a 32bit host.

Correct.

-Chris


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Re: [uml-devel] 2.6.18-skas-v9-pre9 broken

[Blaisorblade]

On Thursday 05 October 2006 23:59, Christopher S. Aker wrote:
> Blaisorblade,
>
> I recently deployed a 2.6.18-skas3-v9-pre9 host, and some users weren't
> able to boot UML beyond "VFS: Mounted root (ext3 filesystem) readonly".
>   As it turns out, only 2.6-um kernels were affected, 2.4-um worked fine.
>
> This happened both in skas3 and skas0 modes.  Jeff graciously took a
> look at some straces, and his comment was that "something broke page
> fault handling generically".
>
> The traces are here:
>
> http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace.txt (skas3)
> http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace_skas0.txt
>
> Reverting back to a skas3-v8.2 kernel fixed it.

An important question: you reverted to a 2.6.18 + skas kernel or a 2.6.17 one? 
A similar bug is being discussed about a regression in 2.6.18 vanilla...
-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade
Chiacchiera con i tuoi amici in tempo reale! 
 http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com 


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Re: [uml-devel] 2.6.18-skas-v9-pre9 broken

[Christopher S. Aker]

Blaisorblade wrote:
> On Thursday 05 October 2006 23:59, Christopher S. Aker wrote:
>> Blaisorblade,
>>
>> I recently deployed a 2.6.18-skas3-v9-pre9 host, and some users weren't
>> able to boot UML beyond "VFS: Mounted root (ext3 filesystem) readonly".
>>   As it turns out, only 2.6-um kernels were affected, 2.4-um worked fine.
>>
>> This happened both in skas3 and skas0 modes.  Jeff graciously took a
>> look at some straces, and his comment was that "something broke page
>> fault handling generically".
>>
>> The traces are here:
>>
>> http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace.txt (skas3)
>> http://www.theshore.net/~caker/uml/skas2.6.18-uml_trace_skas0.txt
>>
>> Reverting back to a skas3-v8.2 kernel fixed it.
> 
> An important question: you reverted to a 2.6.18 + skas kernel or a 2.6.17 one? 
> A similar bug is being discussed about a regression in 2.6.18 vanilla...

Uh, somehow I missed this email for two months...

All my hosts are running at most 2.6.16.x, so this very well could be a 
regression in post 2.6.16 kernels.

-Chris

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Re: [uml-devel] 2.6.18-skas-v9-pre9 broken

[Christopher S. Aker]

Christopher S. Aker wrote:
> Blaisorblade wrote:

>> An important question: you reverted to a 2.6.18 + skas kernel or a 2.6.17 one? 
>> A similar bug is being discussed about a regression in 2.6.18 vanilla...

> All my hosts are running at most 2.6.16.x, so this very well could be a 
> regression in post 2.6.16 kernels.

Confirmed. This is a regression in post 2.6.16.x kernels (well, at least 
2.6.19).  Had a user hit the "VFS: Mounted root (ext3 filesystem) 
readonly" hang on a 2.6.19 kernel with skas3-v8.2, running 2.6.19-um

Any ideas?

-Chris


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