Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754958AbbBBDnK (ORCPT ); Sun, 1 Feb 2015 22:43:10 -0500 Received: from mail-ob0-f174.google.com ([209.85.214.174]:57812 "EHLO mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752423AbbBBDnG (ORCPT ); Sun, 1 Feb 2015 22:43:06 -0500 MIME-Version: 1.0 In-Reply-To: <54CEF123.5050106@oracle.com> References: <54CEECF7.7020504@oracle.com> <54CEF123.5050106@oracle.com> Date: Mon, 2 Feb 2015 09:13:04 +0530 Message-ID: Subject: Re: [PATCH Resend] cpufreq: Set cpufreq_cpu_data to NULL before putting kobject From: Viresh Kumar To: ethan zhao Cc: Rafael Wysocki , santosh shilimkar , Linaro Kernel Mailman List , "linux-pm@vger.kernel.org" , linux-kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1515 Lines: 44 On 2 February 2015 at 09:08, ethan zhao wrote: >> We take cpufreq_driver_lock() here, and so this will >> block thread B. > > No, there is no cpufreq_driver_lock acquired between > > cpufreq_cpu_get() and cpufreq_cpu_put() I am not saying that the lock is taken between them. But within cpufreq_cpu_get() to make sure policy doesn't get freed while we are doing kobject_get(). >>> beginning the deference of policy Thread B: >>> ... ... __cpufreq_remove_dev_finish() >>> cpufreq_policy_free(policy); >>> >>> >>> Perhaps move policy->rwsem out side the policy structure is a way to >>> avoid >>> it completely. >>> and you could stopping the PPC thread stepping forward as my patch as >>> temporary workaround. >> >> I couldn't understand your problem completely. Apart from giving a >> detailed >> look of what's going on both threads, always specify where the BUG >> actually >> is.. > > The problem is you are using a rwsem inside policy structure to protect its > assessment, that is bad design. What is the current bug you are facing right now, I haven't understood it well. Also a lock within the structure isn't new. Its all over the kernel. I don't understand why you say its a bad design. -- viresh -- 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/