[Bug 9475] jiffies counter leaps on CPU frequency changes

[bugme-daemon@bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=9475





------- Comment #5 from stefano.brivio@polimi.it  2007-12-04 14:04 -------
(In reply to comment #4)

> hm, maybe i'm missing something obvious, but adjust_jiffies() seems to 
> fix up loops_per_jiffy, not the jiffies variable. The bugreport included 
> a /var/log/messages snippets that showed printk timestamps - the printk 
> timestamps are directly derived from the 'jiffies' variable. Those 
> timestamps jumped back and forth according to CPU frequency. So 
> _something_ does seem to affect the jiffies variable - and it's not 
> adjust_jiffies(). Or at least so i think.

Yes, I'm wondering about this as well. But so far, I hadn't been able to find
out where in the kernel a CPU frequency switch could trigger a sudden change to
the jiffies counter. The only related thing I observed is that adjust_jiffies()
is called, but that doesn't seem to be the culprit.

BTW, I just sorted out the dm-crypt issue which prevented me to test 2.6.23.
Will let you know ASAP about further tests.


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