From: Ingo Molnar <mingo@elte.hu>
To: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Jeremy Fitzhardinge <jeremy@goop.org>,
Steven Rostedt <srostedt@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sched_clock: prevent scd->clock from moving backwards
Date: Fri, 10 Oct 2008 11:17:11 +0200 [thread overview]
Message-ID: <20081010091711.GA7805@elte.hu> (raw)
In-Reply-To: <1223576490.6394.3.camel@norville.austin.ibm.com>
* Dave Kleikamp <shaggy@linux.vnet.ibm.com> wrote:
> On Thu, 2008-10-09 at 12:54 -0500, Dave Kleikamp wrote:
>
> > I'll fix the patch and retest it before sending it again.
>
> I'm definitely running with the new patch now. Here goes:
> -------------------------------------------------
> 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@linux.vnet.ibm.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
applied to tip/sched/clock, thanks Dave!
Ingo
next prev parent reply other threads:[~2008-10-10 9:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-23 21:04 Definition of sched_clock broken Jeremy Fitzhardinge
2008-10-08 12:59 ` Dave Kleikamp
2008-10-08 13:00 ` [PATCH] sched_clock: prevent scd->clock from moving backwards Dave Kleikamp
2008-10-08 23:05 ` Peter Zijlstra
2008-10-09 9:06 ` Ingo Molnar
2008-10-09 15:17 ` Ingo Molnar
2008-10-09 17:54 ` Dave Kleikamp
2008-10-09 18:21 ` Dave Kleikamp
2008-10-10 9:17 ` Ingo Molnar [this message]
2008-10-09 21:22 ` Ingo Molnar
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