From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.101.70]:59032 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964914AbcA1Kn6 (ORCPT ); Thu, 28 Jan 2016 05:43:58 -0500 Date: Thu, 28 Jan 2016 10:44:34 +0000 From: Juri Lelli To: Viresh Kumar Cc: "Rafael J. Wysocki" , linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, "# v4 . 2+" , open list Subject: Re: [PATCH] cpufreq: Fix NULL reference crash while accessing policy->governor_data Message-ID: <20160128104434.GT10898@e106622-lin> References: <1297c8fc8135f8b5359f9c49d220a939c0ee640e.1453741314.git.viresh.kumar@linaro.org> <3004241.yqvZmcL5vE@vostro.rjw.lan> <20160128021553.GC3935@vireshk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160128021553.GC3935@vireshk> Sender: stable-owner@vger.kernel.org List-ID: On 28/01/16 07:45, Viresh Kumar wrote: > On 27-01-16, 23:54, Rafael J. Wysocki wrote: > > So I've applied this, but I'm not sure it is sufficient yet. > > At least, this solves the crash Juri was hitting on a multi cluster > box. > > > Have you double checked whether or not stuff cannot be reordered by > > the CPU and/or the compiler and no additional memory barriers are needed? > > I don't think CPU will reorder things before a function call. It can > reorder lines, which CPU thinks aren't related but it can't assume the > same in this case. We have tons of code like this. > > @Juri: What do you say? > Yeah, it looks good on my boxes (even though I'll run some more tests later today). I'm not entirely sure either about the reordering, but reordering across a function call (of a different compilation unit) seems quite unlikely to me as well. Best, - Juri