linux-kernel - Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 19 May 2007 19:43:11 -0700
From:	Daniel Walker <dwalker@...sta.com>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	Sergei Shtylyov <sshtylyov@...mvista.com>, linuxppc-dev@...abs.org,
	tglx@...utronix.de, mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver

On Sat, 2007-05-19 at 13:33 +1000, Paul Mackerras wrote: 
> Daniel Walker writes:
> 
> > On Fri, 2007-05-18 at 19:06 +0400, Sergei Shtylyov wrote:
> > >     Well, the decrementer frequency may change, at least in theory (if the bus 
> > > clock changes).
> > 
> > Does that happen very often?
> 
> If it did, gettimeofday would start reporting seriously wrong values,
> since the timebase and the decrementer count at the same rate, and we
> don't have any provision for fixing things up if that rate changed.
> Fortunately there are no powerpc platforms where the rate is
> variable.

In terms of clocksources, gettimeofday() would have to switch to another
clocksource if the decrementer started to act that way .. That's why it
is possible to register more than one clocksource, to allow for the
switching. The decrementer frequency doesn't change even with cpufreq?

Daniel

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/