Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933032AbaD2IEh (ORCPT ); Tue, 29 Apr 2014 04:04:37 -0400 Received: from mail-oa0-f43.google.com ([209.85.219.43]:46088 "EHLO mail-oa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932971AbaD2IEb (ORCPT ); Tue, 29 Apr 2014 04:04:31 -0400 MIME-Version: 1.0 In-Reply-To: <535F565B.6020405@linux.vnet.ibm.com> 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> Date: Tue, 29 Apr 2014 13:34:31 +0530 Message-ID: Subject: Re: [PATCH v2 5/5] cpufreq: Catch double invocations of cpufreq_freq_transition_begin/end From: Viresh Kumar To: "Srivatsa S. Bhat" Cc: "Rafael J. Wysocki" , Meelis Roos , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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))); > 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.. -- 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/