From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: Re: [PATCH 7/8] cpufreq: Preserve policy structure across suspend/resume Date: Mon, 15 Jul 2013 17:23:43 +0530 Message-ID: <51E3E2C7.50107@linux.vnet.ibm.com> References: <20130711221419.547.69781.stgit@srivatsabhat.in.ibm.com> <51E3C950.90503@linux.vnet.ibm.com> <5802844.Fghi6KKD2P@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from e23smtp07.au.ibm.com ([202.81.31.140]:47648 "EHLO e23smtp07.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755907Ab3GOL5Q (ORCPT ); Mon, 15 Jul 2013 07:57:16 -0400 Received: from /spool/local by e23smtp07.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 15 Jul 2013 21:45:00 +1000 In-Reply-To: <5802844.Fghi6KKD2P@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: Viresh Kumar , toralf.foerster@gmx.de, robert.jarzmik@intel.com, durgadoss.r@intel.com, tianyu.lan@intel.com, lantianyu1986@gmail.com, dirk.brandewie@gmail.com, stern@rowland.harvard.edu, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org On 07/15/2013 05:05 PM, Rafael J. Wysocki wrote: > On Monday, July 15, 2013 03:35:04 PM Srivatsa S. Bhat wrote: >> On 07/15/2013 03:25 PM, Viresh Kumar wrote: >>> Hi Srivatsa, >>> >>> I may be wrong but it looks something is wrong in this patch. >>> >>> On 12 July 2013 03:47, Srivatsa S. Bhat >>> wrote: >>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c >>> >>>> @@ -1239,29 +1263,40 @@ static int __cpufreq_remove_dev(struct device *dev, >>>> if ((cpus == 1) && (cpufreq_driver->target)) >>>> __cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT); >>>> >>>> - pr_debug("%s: removing link, cpu: %d\n", __func__, cpu); >>>> - cpufreq_cpu_put(data); >>>> + if (!frozen) { >>>> + pr_debug("%s: removing link, cpu: %d\n", __func__, cpu); >>>> + cpufreq_cpu_put(data); >>> >>> So, we don't decrement usage count here. But we are still increasing >>> counts on cpufreq_add_dev after resume, isn't it? >>> >>> So, we wouldn't be able to free policy struct once all the cpus of a >>> policy are removed after suspend/resume has happened once. >>> >> >> Actually even I was wondering about this while writing the patch and >> I even tested shutdown after multiple suspend/resume cycles, to verify that >> the refcount is messed up. But surprisingly, things worked just fine. >> >> Logically there should've been a refcount mismatch and things should have >> failed, but everything worked fine during my tests. Apart from suspend/resume >> and shutdown tests, I even tried mixing a few regular CPU hotplug operations >> (echo 0/1 to sysfs online files), but nothing stood out. >> >> Sorry, I forgot to document this in the patch. Either the patch is wrong >> or something else is silently fixing this up. Not sure what is the exact >> situation. > > OK, so I'm not going to queue [2-8/8] up until we find out what's going on > here (and until Toralf tells me that it doesn't break his system any more). > Ok, that sounds good. > I've queued up [1/8] for 3.11 already. > Thank you! Regards, Srivatsa S. Bhat