Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754925Ab3CTXQM (ORCPT ); Wed, 20 Mar 2013 19:16:12 -0400 Received: from mail-pb0-f47.google.com ([209.85.160.47]:42496 "EHLO mail-pb0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753651Ab3CTXQL (ORCPT ); Wed, 20 Mar 2013 19:16:11 -0400 Message-ID: <514A4337.6080100@gmail.com> Date: Wed, 20 Mar 2013 16:16:07 -0700 From: David Daney User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Huacai Chen CC: Ralf Baechle , linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, Fuxin Zhang , Zhangjin Wu Subject: Re: [PATCH V2 02/02] MIPS: Init new mmu_context for each possible CPU to avoid memory corruption References: <1363524614-3823-1-git-send-email-chenhc@lemote.com> In-Reply-To: <1363524614-3823-1-git-send-email-chenhc@lemote.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1695 Lines: 46 On 03/17/2013 05:50 AM, Huacai Chen wrote: > Currently, init_new_context() only for each online CPU, this may cause > memory corruption when CPU hotplug and fork() happens at the same time. > To avoid this, we make init_new_context() cover each possible CPU. > > Scenario: > 1, CPU#1 is being offline; > 2, On CPU#0, do_fork() call dup_mm() and copy a mm_struct to the child; > 3, On CPU#0, dup_mm() call init_new_context(), since CPU#1 is offline > and init_new_context() only covers the online CPUs, child has the > same asid as its parent on CPU#1 (however, child's asid should be 0); > 4, CPU#1 is being online; > 5, Now, if both parent and child run on CPU#1, memory corruption (e.g. > segfault, bus error, etc.) will occur. > > Signed-off-by: Huacai Chen We were seeing the same crashes, this patch set seems to fix the problem. Acked-by: David Daney > --- > arch/mips/include/asm/mmu_context.h | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/mips/include/asm/mmu_context.h b/arch/mips/include/asm/mmu_context.h > index e81d719..49d220c 100644 > --- a/arch/mips/include/asm/mmu_context.h > +++ b/arch/mips/include/asm/mmu_context.h > @@ -133,7 +133,7 @@ init_new_context(struct task_struct *tsk, struct mm_struct *mm) > { > int i; > > - for_each_online_cpu(i) > + for_each_possible_cpu(i) > cpu_context(i, mm) = 0; > > return 0; > -- 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/