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

Fabio Comolli
2008-12-13T18:45:18Z

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).