Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756215AbaD2ILj (ORCPT ); Tue, 29 Apr 2014 04:11:39 -0400 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:40777 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752002AbaD2ILg (ORCPT ); Tue, 29 Apr 2014 04:11:36 -0400 Message-ID: <535F5E84.4060903@linux.vnet.ibm.com> Date: Tue, 29 Apr 2014 13:40:44 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Viresh Kumar CC: "Rafael J. Wysocki" , Meelis Roos , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List Subject: Re: [PATCH v2 5/5] cpufreq: Catch double invocations of cpufreq_freq_transition_begin/end References: <20140428185331.28755.899.stgit@srivatsabhat.in.ibm.com> <20140428185507.28755.6483.stgit@srivatsabhat.in.ibm.com> <535F43B2.2000309@linux.vnet.ibm.com> <535F565B.6020405@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14042908-8256-0000-0000-00000CD590FC Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/29/2014 01:34 PM, Viresh Kumar wrote: > On 29 April 2014 13:05, Srivatsa S. Bhat > wrote: >> On 04/29/2014 12:19 PM, Viresh Kumar wrote: >>> + WARN_ON(!(cpufreq_driver->flags & CPUFREQ_ASYNC_NOTIFICATION) >>> && (current == policy->transition_task)); >>> >>> which you already mentioned. >> >> Yeah, I think we should just go with this. I thought we needed lots of >> if-conditions to do exclude these drivers (which would have made it ugly), >> but as you pointed above, just this one would suffice. > > Okay, I think we can do one more modification here: > >>> + WARN_ON(unlikely(!(cpufreq_driver->flags & CPUFREQ_ASYNC_NOTIFICATION) >>> && (current == policy->transition_task))); > WARN_ON and friends already wrap their arguments within unlikely(). So we don't need to add it explicitly. > >> Besides, the cpufreq core doesn't automatically invoke _begin() and >> _end() for ASYNC_NOTIFICATION drivers. So that means the probability >> that such drivers will hit this problem is extremely low, since the >> driver alone is responsible for invoking _begin/_end and hence there >> shouldn't be much of a conflict. So I think we should really just >> skip ASYNC_NOTIFICATION drivers in this debug infrastructure. > > The only way it can happen (I don't hope somebody would be so > stupid to call begin twice from target() :)), is via transition notifiers, > which in some case starting a new transition.. Hmm.. Regards, Srivatsa S. Bhat -- 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/