From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kapileshwar Singh Subject: Re: [PATCH v3 5/5] thermal: cpu_cooling: update the cpu device when cpufreq updates the policy cpu Date: Tue, 03 Mar 2015 15:09:48 +0000 Message-ID: <54F5CEBC.1070303@arm.com> References: <1425316643-31991-1-git-send-email-javi.merino@arm.com> <1425316643-31991-6-git-send-email-javi.merino@arm.com> <54F5941F.6030402@arm.com> <54F59DEF.3020700@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Return-path: Received: from service87.mimecast.com ([91.220.42.44]:43974 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755159AbbCCPJw convert rfc822-to-8bit (ORCPT ); Tue, 3 Mar 2015 10:09:52 -0500 In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Viresh Kumar Cc: Javi Merino , Eduardo Valentin , Zhang Rui , Linux PM list , "linux-kernel@vger.kernel.org" , Punit Agrawal , Lina Iyer , Mark Brown , Jon Medhurst On 03/03/15 13:07, Viresh Kumar wrote: > On 3 March 2015 at 17:11, Kapileshwar Singh wrote: >> Yes I indeed tested the case where we cache the device pointer of the CPU for which the OPP's are populated. >> When this CPU is hotplugged out, it invalidates the device pointer itself. Here are the error we get in dmesg: > > What do you mean by 'invalidates the device pointer' ? that cpu_dev is NULL ? The cpu_dev is not NULL but we get an erroneous OPP back. We found the problem lies in the way we calculate the frequency for the cluster. >> <3>[67203.216774] opp_get_voltage: Invalid parameters >> <3>[67203.326774] opp_get_voltage: Invalid parameters >> <3>[67203.326774] opp_get_voltage: Invalid parameters > > Have you handwritten them ? Why don't they precede with dev_pm_* ?? I have not handwritten them, It was from a Linaro 3.10 based kernel when I first noticed this issue but the same problem exists in mainline. Apologies for this I sent you an older trace which I had saved when I found the bug. Here is the trace I get from mainline [ 5680.135339] dev_pm_opp_get_voltage: Invalid parameters [ 5680.245528] dev_pm_opp_get_voltage: Invalid parameters [ 5680.355432] dev_pm_opp_get_voltage: Invalid parameters [ 5680.465521] dev_pm_opp_get_voltage: Invalid parameters [ 5680.575599] dev_pm_opp_get_voltage: Invalid parameters [ 5680.685817] dev_pm_opp_get_voltage: Invalid parameters [ 5680.795556] dev_pm_opp_get_voltage: Invalid parameters [ 5680.905598] dev_pm_opp_get_voltage: Invalid parameters > >> >> Which happens because: >> >> unsigned long dev_pm_opp_get_voltage(struct dev_pm_opp *opp) >> { >> .. >> tmp_opp = rcu_dereference(opp); >> if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available) >> pr_err("%s: Invalid parameters\n", __func__); > > This %s should print routine name .. > >> else >> .. >> >> Which happens when >> >> opp = dev_pm_opp_find_freq_exact(cpufreq_device->cpu_dev, freq_hz, >> true); >> >> returns a an erroneous or NULL OPP or the opp is unavailable (in the above condition) > Update: This returns an erroneous OPP > Please goto the depth of this thing, as I don't think it should happen. > > Over that I was asking you if you have tested the solution Javi gave, > because OPPs > wouldn't have been initialized for other CPUs once policy->cpu goes down. I did test this but we were working with the assumption that OPPs should be populated for all the CPUs and also that OPPs are lost for a hotplugged CPU which I see is not the case. We have looked at this more closely and found that problem lies in: freq = cpufreq_quick_get(cpumask_any(&cpufreq_device->allowed_cpus)); which returns a NULL frequency as we are not checking for online CPUs here. We shall come up with a fix for this. Many thanks for helping us with the investigation. Regards, KP