From: bugme-daemon@bugzilla.kernel.org
Subject: [Bug 9475] jiffies counter leaps on CPU frequency changes
Date: Tue,  4 Dec 2007 13:47:07 -0800 (PST)
Message-ID: <20071204214707.3DD26108069@picon.linux-foundation.org>
References: <bug-9475-3570@http.bugzilla.kernel.org/>
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http://bugzilla.kernel.org/show_bug.cgi?id=9475


------- Comment #4 from mingo@elte.hu  2007-12-04 13:47 -------

> we've been doing adjust_jiffies() on cpu speed transitions forever, so 
> this isn't a regression in that sense.  Why it's causing a problem now 
> is a mystery though.
> 
> Even more puzzling, on lkml, Stefano commented out the 
> adjust_jiffies() code, and still saw leaping counters, so I'm really 
> at a loss to explain what's going on.

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.


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