From mboxrd@z Thu Jan 1 00:00:00 1970 From: john stultz Subject: Re: [PATCH V8 02/13] ntp: add ADJ_SETOFFSET mode bit Date: Mon, 10 Jan 2011 13:06:37 -0800 Message-ID: <1294693597.3068.12.camel@work-vm> References: <20110108175028.GA22308@riccoc20.at.omicron.at> <1294678145.3068.6.camel@work-vm> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Kuwahara,T." <6vvetjsrt26xsrzlh1z0zn4d2grdah-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Cc: Richard Cochran , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alan Cox , Arnd Bergmann , Christoph Lameter , David Miller , Krzysztof Halasa , Peter Zijlstra , Rodolfo Giometti , Thomas Gleixner List-Id: linux-api@vger.kernel.org On Tue, 2011-01-11 at 05:45 +0900, Kuwahara,T. wrote: > On Tue, Jan 11, 2011 at 1:49 AM, john stultz wrote: > > Leapsecond processing is done via an absolute hrtimer. Thus when the > > time offset is set, the hrtimers that should have expired will fire > > (just like with settimeofday) and the adjustment will then be made. > > How do you convert relative time to absolute time? It's not trivial > because TAI offset is also a variable. I don't believe I understand what you're getting at. The proposed interface is almost identical in functionality to a userland application doing the following: offset = my_calculate_offset(); clock_gettime(CLOCK_REALTIME, &now); newtime = my_add_ts(now, offset); settimeofday(&newtime, 0); The only difference is that you avoid the error from the delay between the gettime call and the settime call. It just adds the offset directly to the CLOCK_REALTIME. thanks -john