linux-kernel - Re: [Bug #12667] Badness at kernel/time/timekeeping.c:98 in pmud (timekeeping

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Message-Id: <200902192223.05361.rjw@sisk.pl>
Date:	Thu, 19 Feb 2009 22:23:04 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Collins <paul@...ly.ondioline.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [Bug #12667] Badness at kernel/time/timekeeping.c:98 in pmud (timekeeping_suspended)

On Thursday 19 February 2009, Thomas Gleixner wrote:
> On Thu, 19 Feb 2009, Benjamin Herrenschmidt wrote:
> 
> > On Thu, 2009-02-19 at 21:27 +1300, Paul Collins wrote:
> > > > Just for laughs I slapped together the following, which seems to do
> > > the
> > > > job, although not especially tidily.
> > > 
> > > And it doesn't even do the job.  Judging by this new trace, submitting
> > > input events from the via-pmu resume function is still too early.
> > > 
> > What's up Thomas ? We can't call gettimeofday() from a sysdev
> > suspend/resume ? That's a little bit too harsh no ?
> 
> Well, harsh or not is not the question here. 
> 
> Fact is that you call gettimeofday() _before_ the timekeeping code has
> resumed.
> 
> That's a simple ordering problem. timekeeping is in the sysdev class
> as well and it's not the only sysdev which has explicit ordering
> requirements.

Do we need suspend-resume priorities for sysdevs?  Such that sysdevs
with a higher priority will always be suspended earlier and resumed later
than sysdevs with lower priority (or the other way around)?

Rafael
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