Re: [Bug #12155] Regression in 2.6.28-rc and 2.6.27-stable - hibernate related

Ingo Molnar
2008-12-16T19:07:07Z

* Rafael J. Wysocki <rjw-KKrjLPT3xs0@public.gmane.org> wrote:

> On Saturday, 13 of December 2008, Fabio Comolli wrote:
> > Hi.
>
> Hi,
>
> > On Sat, Dec 13, 2008 at 5:33 PM, Rafael J. Wysocki <rjw-KKrjLPT3xs0@public.gmane.org> wrote:
> > > This message has been generated automatically as a part of a report
> > > of recent regressions.
> > >
> > > The following bug entry is on the current list of known regressions
> > > from 2.6.27. Please verify if it still should be listed and let me know
> > > (either way).
> > >
> > >
> > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12155
> > > Subject : Regression in 2.6.28-rc and 2.6.27-stable - hibernate related
> > > Submitter : Fabio Comolli <fabio.comolli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> > > Date : 2008-11-23 16:17 (21 days old)
> > > References : http://marc.info/?l=linux-kernel&m=122745709926361&w=4
> >
> > Still present. It has been bisected to:
> >
> > ---------------------------------------------------------------------------------------------------------------
> > commit 5e55aa8db085dad1aabb4574c73c23c7ae571e7b
> > Author: Dave Kleikamp <shaggy-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> > Date: Sun Oct 26 18:20:14 2008 -0400
> >
> > sched_clock: prevent scd->clock from moving backwards
> >
> > commit 5b7dba4ff834259a5623e03a565748704a8fe449 upstream
> >
> > sched_clock: prevent scd->clock from moving backwards
> >
> > When sched_clock_cpu() couples the clocks between two cpus, it may
> > increment scd->clock beyond the GTOD tick window that __update_sched_clock()
> > uses to clamp the clock. A later call to __update_sched_clock() may move
> > the clock back to scd->tick_gtod + TICK_NSEC, violating the clock's
> > monotonic property.
> >
> > This patch ensures that scd->clock will not be set backward.
> >
> > Signed-off-by: Dave Kleikamp <shaggy-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> > Acked-by: Peter Zijlstra <a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org>
> > Signed-off-by: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>
> > Cc: Chuck Ebbert <cebbert-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh-l3A5Bk7waGM@public.gmane.org>
> > ------------------------------------------------------------------------------------------------------------
> >
> > Both 2.6.27.8 and 2.6.28-rc8 with that commit reverted work fine
> > (well, at least they failed to show the bug so far).
>
> Thanks for the update, I have put this information into the Bugzilla entry.
>
> Would everyone involved agree with reverting the above commit for now
> and revisiting the issue in the 2.6.29 time frame?

yeah - i think it's too late to do anything but a revert here.

Ingo