From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: [PATCH 19/21] cpuidle: create list of registered drivers Date: Thu, 26 Sep 2013 10:19:14 +0200 Message-ID: <5243EE02.9020207@linaro.org> References: <7e9565e323c1e065eeb2a2a1075967bd21ee6066.1379779777.git.viresh.kumar@linaro.org> <5243641B.6050604@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-wg0-f53.google.com ([74.125.82.53]:57624 "EHLO mail-wg0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751060Ab3IZITT (ORCPT ); Thu, 26 Sep 2013 04:19:19 -0400 Received: by mail-wg0-f53.google.com with SMTP id x12so221362wgg.32 for ; Thu, 26 Sep 2013 01:19:18 -0700 (PDT) In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Viresh Kumar Cc: "Rafael J. Wysocki" , Lists linaro-kernel , Patch Tracking , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List 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 protec= t >> 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 o= r >> semaphores should be used here". >> >> A lock has been introduced in this function already and the system h= angs >> with 1024 cpus. > > Hmm... I see.. I didn't knew about this expectation.. What about a rc= u > 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/083= 054.html --=20 Linaro.org =E2=94=82 Open source software fo= r ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog