Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755498AbbLDIa7 (ORCPT ); Fri, 4 Dec 2015 03:30:59 -0500 Received: from mail-wm0-f51.google.com ([74.125.82.51]:38321 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755275AbbLDIa6 (ORCPT ); Fri, 4 Dec 2015 03:30:58 -0500 Date: Fri, 4 Dec 2015 09:30:54 +0100 From: Ingo Molnar To: Xunlei Pang Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Ingo Molnar , Steven Rostedt , Rusty Russell Subject: Re: [PATCH] sched/core: Clear the root_domain cpumasks in init_rootdomain() Message-ID: <20151204083054.GB32345@gmail.com> References: <1449057179-29321-1-git-send-email-xlpang@redhat.com> <20151202123414.GB9928@worktop.ger.corp.intel.com> <565EEE3E.30301@redhat.com> <20151202162542.GT3816@twins.programming.kicks-ass.net> <565FAC78.3030205@redhat.com> <20151203082800.GA2321@gmail.com> <56602D19.5080308@redhat.com> <20151204080901.GA26934@gmail.com> <56614EAC.1010804@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56614EAC.1010804@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2112 Lines: 60 * Xunlei Pang wrote: > Hi Ingo, > > On 12/04/2015 at 04:09 PM, Ingo Molnar wrote: > > * Xunlei Pang wrote: > > > >>> Hm, is the alloc_cpumask_var() done in alloc_sched_domains() safe? > >> Until now, I haven't found any other similar issues, but I will check further. > >> > >>> At least the usage pattern in init_sched_domains() looks unsafe: > >>> > >>> doms_cur = alloc_sched_domains(ndoms_cur); > >>> if (!doms_cur) > >>> doms_cur = &fallback_doms; > >>> cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map); > > So is this pattern in init_sched_domains() correct, for OFFSTACK=y? > > > > It looks wrong to me, as alloc_sched_domains() allocates an uninitialized cpumask > > via alloc_cpumask_var() and returns it: > > > > cpumask_var_t *alloc_sched_domains(unsigned int ndoms) > > { > > int i; > > cpumask_var_t *doms; > > > > doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL); > > if (!doms) > > return NULL; > > for (i = 0; i < ndoms; i++) { > > if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) { > > free_sched_domains(doms, i); > > return NULL; > > } > > } > > return doms; > > } > > > > and then this code: > > > >>> cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map); > > uses it without first clearing it. > > > > So is this another such bug, or am I missing something? > > Yeah, I noticed that as well. But fortunately cpumask_andnot(), > cpumask_and() and the like will clear doms_cur[] indirectly, also > cpu_isolated_map, cpu_active_mask, etc doesn't contain any > garbage bits. I also checked the use of it by cpuset, no extra such > bug found by me so far. Great, thanks for double checking! Ingo -- 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/