From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: Re: [RFC v3] cpufreq: Make sure frequency transitions are serialized Date: Thu, 20 Mar 2014 15:15:59 +0530 Message-ID: <532AB8D7.5000608@linux.vnet.ibm.com> References: <2efc621827cbd96a05a3d34075154974b4816ecd.1394782795.git.viresh.kumar@linaro.org> <532840FD.308@linux.vnet.ibm.com> <53296870.5010505@linux.vnet.ibm.com> <53298A7D.3080400@linux.vnet.ibm.com> <532AA7A8.3040508@linux.vnet.ibm.com> <532AB3E7.3090503@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Viresh Kumar Cc: "Rafael J. Wysocki" , Lists linaro-kernel , "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List , Amit Daniel List-Id: linux-pm@vger.kernel.org On 03/20/2014 03:03 PM, Viresh Kumar wrote: > On 20 March 2014 14:54, Srivatsa S. Bhat > wrote: >> On 03/20/2014 02:07 PM, Viresh Kumar wrote: >>> WARN_ON(policy->transition_ongoing); >>> >> >> I guess you meant WARN_ON(!policy->transition_ongoing) >> perhaps? > > Ooops!! > >> I'm not sure whether its really worth it, because it kinda looks >> obvious. Not sure what kind of bugs it would catch. I can't think of any >> such scenario :-( > > Just to catch if somebody is sending a POSTCHANGE one without first > sending a PRECHANGE one.. Just another check to make sure things are > in order. > Well, that's unlikely, since they will have to call _end() before _begin() :-) That's the power of having great function names - they make it impossible to use them incorrectly ;-) But anyway, I can add the check, just in case somebody misses even such an obvious cue! :-) By the way, I'm also thinking of using a spinlock instead of a mutex. The critical section is tiny and we don't sleep inside the critical section - sounds like the perfect case for a spinlock. Regards, Srivatsa S. Bhat