Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752854Ab3FZR5c (ORCPT ); Wed, 26 Jun 2013 13:57:32 -0400 Received: from mail-db9lp0251.outbound.messaging.microsoft.com ([213.199.154.251]:8186 "EHLO db9outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752759Ab3FZR5b (ORCPT ); Wed, 26 Jun 2013 13:57:31 -0400 X-Forefront-Antispam-Report: CIP:163.181.249.109;KIP:(null);UIP:(null);IPV:NLI;H:ausb3twp02.amd.com;RD:none;EFVD:NLI X-SpamScore: -2 X-BigFish: VPS-2(zz98dI1432Izz1f42h1ee6h1de0h1fdah1202h1e76h1d1ah1d2ah1fc6hzz8275bhz2dh668h839h944hd25hd2bhf0ah1220h1288h12a5h12a9h12bdh137ah13b6h1441h1504h1537h153bh162dh1631h1758h18e1h1946h19b5h1ad9h1b0ah1d0ch1d2eh1d3fh1dfeh1dffh1e1dh1155h) X-WSS-ID: 0MP0HVN-02-N88-02 X-M-MSG: Date: Wed, 26 Jun 2013 12:57:22 -0500 From: Jacob Shin To: Viresh Kumar CC: Tim Gardner , "Rafael J. Wysocki" , LKML , , Subject: Re: od_set_powersave_bias: NULL pointer dereference Message-ID: <20130626175722.GA20226@jshin-Toonie> References: <51C87ADC.4070409@canonical.com> <20130625161935.GA10208@jshin-Toonie> <20130626142852.GA2326@jshin-Toonie> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginatorOrg: amd.com X-FOPE-CONNECTOR: Id%0$Dn%*$RO%0$TLS%0$FQDN%$TlsDn% Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1324 Lines: 35 On Wed, Jun 26, 2013 at 08:02:29PM +0530, Viresh Kumar wrote: > On 26 June 2013 19:58, Jacob Shin wrote: > > On Wed, Jun 26, 2013 at 12:18:27PM +0530, Viresh Kumar wrote: > > >> I am not sure if this is enough. What if we had ondemand as the > >> governor initially, then we changed it to something else. Now also > >> cur_policy contains a address and isn't zero. I just tested this case with this patch applied, and did not have any problems. > >> > >> > cpumask_or(&done, &done, policy->cpus); > >> > + > >> > + if (policy->governor != &cpufreq_gov_ondemand) > >> > + continue; > > > > This should catch that case no ? > > Policy might be freed and reallocated by then. And so doing > policy->governor is dangerous. Are you worried that after we have passed the above if check, and before we access ->tuner governor change might occur? Is there something synonymous to get/put_online_cpus() for cpufreq to prevent governor change while we update ->tuner values? Otherwise, should just spinlock? -- 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/