From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755691Ab2DJH5Z (ORCPT ); Tue, 10 Apr 2012 03:57:25 -0400 Received: from e28smtp02.in.ibm.com ([122.248.162.2]:59181 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754917Ab2DJH5X (ORCPT ); Tue, 10 Apr 2012 03:57:23 -0400 From: Nikunj A Dadhania To: paulmck@linux.vnet.ibm.com, "Srivatsa S. Bhat" Cc: Peter Zijlstra , Arjan van de Ven , Steven Rostedt , "rusty\@rustcorp.com.au" , "Rafael J. Wysocki" , Srivatsa Vaddagiri , "akpm\@linux-foundation.org" , Paul Gortmaker , Milton Miller , "mingo\@elte.hu" , Tejun Heo , KOSAKI Motohiro , linux-kernel , Linux PM mailing list Subject: Re: CPU Hotplug rework In-Reply-To: <20120409164628.GA2430@linux.vnet.ibm.com> References: <4F674649.2000300@linux.vnet.ibm.com> <4F67474A.20707@linux.vnet.ibm.com> <20120405173918.GC8194@linux.vnet.ibm.com> <20120405175549.GA9127@linux.vnet.ibm.com> <20120405230654.GB19607@linux.vnet.ibm.com> <4F7F4EF0.70305@linux.vnet.ibm.com> <20120409164628.GA2430@linux.vnet.ibm.com> User-Agent: Notmuch/0.6.1 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-redhat-linux-gnu) Date: Tue, 10 Apr 2012 13:26:55 +0530 Message-ID: <87d37gxbnc.fsf@abhimanyu.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii x-cbid: 12041007-5816-0000-0000-000002146D34 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 9 Apr 2012 09:46:28 -0700, "Paul E. McKenney" wrote: > > > > 2. Read and understand the architecture-specific code, looking > > > for opportunities to consolidate additional function into > > > core code. > > > > > > a. Carry out any indicated consolidation. > > > > > > b. Convert all architectures to make use of the > > > consolidated implementation. > > > > > > Not started. Low priority from a big.LITTLE perspective. > > > > > > Recently this unexpectedly assumed high priority due to some scheduler > > changes and things got fixed up temporarily. And in that context, > > Peter Zijlstra gave some more technical pointers on what is wrong and needs > > to be done right. Link: https://lkml.org/lkml/2012/3/22/149 > > > > Nikunj (in CC) has offered to work with me on this consolidation. > > Very cool! I have added the following: > > ------------------------------------------------------------------------ > > CONSOLIDATE ARCHITECTURE-SPECIFIC CPU-HOTPLUG CODE > > 1. Ensure that all CPU_STARTING notifiers complete before the > incoming CPU is marked online (the blackfin architecture > fails to do this). > > 2. Ensure that interrupts are disabled throughout the CPU_STARTING > notifiers. Currently, blackfin, cris, m32r, mips, sh, sparc64, > um, and x86 fail to do this properly. > > 3. Ensure that all architectures that use CONFIG_USE_GENERIC_SMP_HELPERS > hold ipi_call_lock() over the entire CPU-online process. Currently, > alpha, arm, m32r, mips, sh, and sparc32 seem to fail to do this > properly. > > 4. Additional memory barriers are likely to be needed, for example, > an smp_wmb() after setting cpu_active and an smp_rmb() in > select_fallback_rq() before reading cpu_active. > > Srivatsa Bhat (srivatsa.bhat@linux.vnet.ibm.com) and Nikunj A Dadhania > (nikunj@linux.vnet.ibm.com) are taking on this work. > Sounds good :-) Regards Nikunj