From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754087Ab3ISNRm (ORCPT ); Thu, 19 Sep 2013 09:17:42 -0400 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:56373 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752737Ab3ISNRk (ORCPT ); Thu, 19 Sep 2013 09:17:40 -0400 Message-ID: <523AF50E.1040502@linux.vnet.ibm.com> Date: Thu, 19 Sep 2013 18:28:54 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Linus Walleij CC: "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Viresh Kumar Subject: Re: Regression on cpufreq in v3.12-rc1 References: <45987104.t6r4hvPgQn@vostro.rjw.lan> <523AF22F.1010909@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13091913-8256-0000-0000-0000094AF30C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/19/2013 06:25 PM, Linus Walleij wrote: > On Thu, Sep 19, 2013 at 2:46 PM, Srivatsa S. Bhat > wrote: > >>>> I don't really know if this is the right solution at all, so please >>>> help me out here... if you want that patch I can send it once >>>> I understand this properly. >> >> IIRC, recent kernels didn't return 0 or any error code when the !policy >> condition was matched. So can you check whether this problem occurs with >> 3.11 or 3.10 as well? > > v3.11 works fine. > > The problem is not what it returns, the system seems to survive no matter > whether it returns 0 or 17 or whatever. > Of course. What I intended to say was that I don't recall recent kernels returning _anything_ on !policy. So there wasn't any sudden change in _that_ piece of code, AFAIR. > The problem is that sometimes in the v3.12 kernel cycle we got a > BUG() crash instead of some random value back for calling early. > Yep, and that's most likely due to some change in ordering of calls somewhere, which makes calls to lock_policy_rwsem_read() before it is safe to do so, rather than anything related to how lock_policy_rwsem_read() handles the call. >> So I think we should first identify (bisect?) and understand what caused that >> particular change and then we will be in a position to evaluate whether the >> patch you proposed would be the right fix or not. > > I'll see if I can get a bisect going, the problem is that I upload the > kernel over the serial port so this isn't a very quick procedure :-( > Hmmm.. :-/ Regards, Srivatsa S. Bhat