Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755599Ab3I3Shv (ORCPT ); Mon, 30 Sep 2013 14:37:51 -0400 Received: from mail-we0-f174.google.com ([74.125.82.174]:56620 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755300Ab3I3Shu (ORCPT ); Mon, 30 Sep 2013 14:37:50 -0400 Message-ID: <5249C4FB.1060705@linaro.org> Date: Mon, 30 Sep 2013 20:37:47 +0200 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Viresh Kumar , "Rafael J. Wysocki" , Lists linaro-kernel , Patch Tracking , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List Subject: Re: [PATCH 19/21] cpuidle: create list of registered drivers References: <7e9565e323c1e065eeb2a2a1075967bd21ee6066.1379779777.git.viresh.kumar@linaro.org> <5243641B.6050604@linaro.org> <5243EE02.9020207@linaro.org> <20130928213343.GA19582@linux.vnet.ibm.com> In-Reply-To: <20130928213343.GA19582@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1577 Lines: 43 On 09/28/2013 11:33 PM, Paul E. McKenney wrote: > On Thu, Sep 26, 2013 at 10:19:14AM +0200, Daniel Lezcano wrote: >> On 09/26/2013 08:17 AM, Viresh Kumar wrote: >>> On 26 September 2013 04:00, Daniel Lezcano wrote: >>>> If you introduce a list, you will have to introduce a lock to protect >>>> it. >>> >>> I missed it, should have added that :) >>> >>>> This lock will be in the fast path cpuidle_idle_call with the >>>> get_driver function and conforming to the comment: "NOTE: no locks or >>>> semaphores should be used here". >>>> >>>> A lock has been introduced in this function already and the system hangs >>>> with 1024 cpus. >>> >>> Hmm... I see.. I didn't knew about this expectation.. What about a rcu >>> read/write lock? As far as I know its too lightweight... Can we have that >>> in fast path? >> >> Nope, we can't use rcu in the idle path :) >> >> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-February/083054.html > > But you should be able to use SRCU in the idle path, if that helps. Interesting, thanks for the pointer. -- Daniel -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/