From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935040Ab3FSRNp (ORCPT ); Wed, 19 Jun 2013 13:13:45 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:25956 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934924Ab3FSRNm (ORCPT ); Wed, 19 Jun 2013 13:13:42 -0400 Date: Wed, 19 Jun 2013 13:13:21 -0400 From: Konrad Rzeszutek Wilk To: John Stultz Cc: David Vrabel , xen-devel@lists.xen.org, linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH 2/4] time: add a notifier chain for when the system time is stepped Message-ID: <20130619171321.GE13046@phenom.dumpdata.com> References: <1371655523-15609-1-git-send-email-david.vrabel@citrix.com> <1371655523-15609-3-git-send-email-david.vrabel@citrix.com> <51C1E1B6.8090203@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51C1E1B6.8090203@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 19, 2013 at 09:52:06AM -0700, John Stultz wrote: > On 06/19/2013 08:25 AM, David Vrabel wrote: > >From: David Vrabel > > > >The high resolution timer code gets notified of step changes to the > >system time with clock_was_set() or clock_was_set_delayed() calls. If > >other parts of the kernel require similar notification there is no > >clear place to hook into. > > > >Add a clock_was_set atomic notifier chain > >(clock_was_set_notifier_list) and call this in place of > >clock_was_set(). If the timekeeping locks are held, the calls are > >deferred to a new tasklet. > > > >The hrtimer code adds a notifier block to this chain and uses it to > >call (the now internal) clock_was_set(). Since the timekeeping code > >does not call the chain from the timer irq clock_was_set_delayed() and > >associated code can be removed. > > So on my initial quick review, this *looks* pretty reasonable. I get > a little worried about interface abuse (ie: random drivers trying to > hook into clock_was_set_notifier_list), but we can move that into > timekeeper_internal.h or something similar to limit that. > > The other issue here is we've been burned pretty badly in the past > with changes to clock_was_set(), as its key to keeping timers in > line with timekeeping. So this will need a fair amount of testing > and run time before this gets merged, so 3.12 is what we'd be > targeting at the earliest (its getting a bit late for taking changes > for 3.11 anyway). I think we have four weeks left? Or you think Linus is going to release at the end of the month? > > If you want to try to push patch 1/4 in for 3.11 via the Xen tree, Done. > I'll see about queuing the other three for hopefully 3.12. OK, let me run them through the testing gauntleet to have the warm fuzzy feeling. > > thanks > -john >