From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: Setting monotonic time? Date: Wed, 03 Oct 2018 08:14:25 +0200 Message-ID: <87in2jo8u6.fsf@xmission.com> References: <20180919205037.9574-1-dima@arista.com> <874lej6nny.fsf@xmission.com> <20180924205119.GA14833@outlook.office365.com> <874leezh8n.fsf@xmission.com> <20180925014150.GA6302@outlook.office365.com> <87zhw4rwiq.fsf@xmission.com> <87mus1ftb9.fsf@xmission.com> <877ej2xc23.fsf_-_@xmission.com> <87in2jskew.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: (Thomas Gleixner's message of "Wed, 3 Oct 2018 07:25:35 +0200 (CEST)") Sender: linux-kernel-owner@vger.kernel.org To: Thomas Gleixner Cc: Arnd Bergmann , avagin@virtuozzo.com, dima@arista.com, Linux Kernel Mailing List , 0x7f454c46@gmail.com, adrian@lisas.de, Andy Lutomirski , Christian Brauner , gorcunov@openvz.org, "H. Peter Anvin" , Ingo Molnar , Jeff Dike , Oleg Nesterov , xemul@virtuozzo.com, Shuah Khan , containers@lists.linux-foundation.org, criu@openvz.org, Linux API , the arch/x86 maintainers , Alexey Dobriyan , linux-kselftest@vger.kernel.org List-Id: linux-api@vger.kernel.org Thomas Gleixner writes: > On Wed, 3 Oct 2018, Eric W. Biederman wrote: >> Direct access to hardware/drivers and not through an abstraction like >> the vfs (an abstraction over block devices) can legitimately be handled >> by hotplug events. I unplug one keyboard I plug in another. >> >> I don't know if the input layer is more of a general abstraction >> or more of a hardware device. I have not dug into it but my guess >> is abstraction from what I have heard. >> >> The scary difficulty here is if after restart input is reporting times >> in CLOCK_MONOTONIC and the applications in the namespace are talking >> about times in CLOCK_MONOTONIC_SYNC. Then there is an issue. As even >> with a fixed offset the times don't match up. >> >> So a time namespace absolutely needs to do is figure out how to deal >> with all of the kernel interfaces reporting times and figure out how to >> report them in the current time namespace. > > So you want to talk to Arnd who is leading the y2038 effort. He knowns how > many and which interfaces are involved aside of the obvious core timer > ones. It's quite an amount and the problem is that you really need to do > that at the interface level, because many of those time stamps are taken in > contexts which are completely oblivious of name spaces. Ditto for timeouts > and similar things which are handed in through these interfaces. Yep. That sounds right. Eric