Re: [Xen-devel] Soft lockup/Time went backwards in latest unstable

[Derek Murray <Derek.Murray@xxxxxxxxxxxx>]

On 26 Feb 2007, at 13:22, Keir Fraser wrote:

> There were big changes to Linux's time handling between
> 2.6.16 and 2.6.18 so bugs may hav ebeen introduced while porting  
> out own
> timer code. It might be worth diffing the file time-xen.c from  
> working and
> non-working Linux kernels. It's weird that the failure mode is bad  
> on the
> T60p yet noone else has reported this bug, nor has our testing  
> reproduced
> it. :-(
Some more information on the bug hunt in progress, in case anyone  
with more experience has any ideas:
* Changeset 13508 (i.e. the last one before the transition to a  
2.6.17 kernel) fails in the same way as the current unstable, but it  
uses a 2.6.16.33 kernel.
* Changeset 13213 (which introduced the idle=poll option in the  
kernel when running on Xen) also fails with a 2.6.16.33 kernel.
* Changeset 13216 fails to boot at all (or, at least, locks up for >=  
30 seconds on boot).
* Changeset 13217 ("Make sure we always have a sensible idle  
function; this fixed problems") fails with time going backwards.
* Changeset 13212, however, works.

The only relevant changes between changesets 13212 and 13213 apply to  
the file linux-2.6-xen-sparse/arch/i386/kernel/process-xen.c (and the  
corresponding x86_64 file), to which a poll_idle() function has been  
added. I don't quite understand the significance of this, but could  
it be responsible for the bug that I'm seeing?
Regards,

Derek Murray.

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