From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 11 Jul 2012 14:45:39 +0200 (CEST) From: Thomas Gleixner To: Prarit Bhargava cc: John Stultz , Linux Kernel , Ingo Molnar , Peter Zijlstra , stable@vger.kernel.org Subject: Re: [PATCH 1/6] hrtimer: Provide clock_was_set_delayed() In-Reply-To: <4FFD6E5A.9060206@redhat.com> Message-ID: References: <1341960205-56738-1-git-send-email-johnstul@us.ibm.com> <1341960205-56738-2-git-send-email-johnstul@us.ibm.com> <4FFD6E5A.9060206@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: On Wed, 11 Jul 2012, Prarit Bhargava wrote: > On 07/10/2012 06:43 PM, John Stultz wrote: > > clock_was_set() cannot be called from hard interrupt context because > > it calls on_each_cpu(). For fixing the widely reported leap seconds > > issue it's necessary to call it from the timer interrupt context. > > > > Provide a new function which denotes it in the hrtimer cpu base > > structure of the cpu on which it is called and raising the timer > > softirq. > > > > We then execute the clock_was_set() notificiation in the timer softirq > > context in hrtimer_run_pending(). > > I wish there was a nicer way to do this ... but looking at the code I can't > figure out a better way. (no offense John, it's just the way the code is ;) ) Yeah, I had the same discussion with Peter earlier today. There is only a rather limited set of options. 1) Retrigger the timer interrupt vectors on all CPUs - except the one we are running on, but we have no interface for that at the moment 2) Do the nasty __smp_call_function_single() hack Preallocate call_single_data for all cpus and do a __smp_call_function_single() on all online cpus. This can be called from hard interrupt context or irq disabled regions. That would allow to get rid of the whole delay magic all together. Thoughts? tglx