From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751829AbcBOFKH (ORCPT ); Mon, 15 Feb 2016 00:10:07 -0500 Received: from mail-pa0-f66.google.com ([209.85.220.66]:36569 "EHLO mail-pa0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751080AbcBOFKE (ORCPT ); Mon, 15 Feb 2016 00:10:04 -0500 Message-ID: <1455512997.16012.24.camel@gmail.com> Subject: Re: [PATCH V3] powerpc/mm: Fix Multi hit ERAT cause by recent THP update From: Balbir Singh To: "Aneesh Kumar K.V" , benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, akpm@linux-foundation.org, Mel Gorman , "Kirill A. Shutemov" Cc: linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Mon, 15 Feb 2016 16:09:57 +1100 In-Reply-To: <87lh6mfv2j.fsf@linux.vnet.ibm.com> References: <1454980831-16631-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1455504278.16012.18.camel@gmail.com> <87lh6mfv2j.fsf@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.4 (3.18.4-1.fc23) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Now we can't depend for mm_cpumask, a parallel find_linux_pte_hugepte > can happen outside that. Now i had a variant for kick_all_cpus_sync that > ignored idle cpus. But then that needs more verification. > > http://article.gmane.org/gmane.linux.ports.ppc.embedded/81105 Can be racy as a CPU moves from non-idle to idle In > +     pmd_hugepage_update(vma->vm_mm, address, pmdp, ~0UL, 0); > +     /* > +      * This ensures that generic code that rely on IRQ disabling > +      * to prevent a parallel THP split work as expected. > +      */ > +     kick_all_cpus_sync(); pmdp_invalidate()->pmd_hugepage_update() can still run in parallel with  find_linux_pte_or_hugepte() and race.. Am I missing something? Balbir Singh From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id 6017A6B0005 for ; Mon, 15 Feb 2016 00:10:05 -0500 (EST) Received: by mail-pa0-f46.google.com with SMTP id fl4so67761044pad.0 for ; Sun, 14 Feb 2016 21:10:05 -0800 (PST) Received: from mail-pa0-x241.google.com (mail-pa0-x241.google.com. [2607:f8b0:400e:c03::241]) by mx.google.com with ESMTPS id 5si40757773pfq.204.2016.02.14.21.10.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 14 Feb 2016 21:10:04 -0800 (PST) Received: by mail-pa0-x241.google.com with SMTP id zv9so940116pab.0 for ; Sun, 14 Feb 2016 21:10:04 -0800 (PST) Message-ID: <1455512997.16012.24.camel@gmail.com> Subject: Re: [PATCH V3] powerpc/mm: Fix Multi hit ERAT cause by recent THP update From: Balbir Singh Date: Mon, 15 Feb 2016 16:09:57 +1100 In-Reply-To: <87lh6mfv2j.fsf@linux.vnet.ibm.com> References: <1454980831-16631-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1455504278.16012.18.camel@gmail.com> <87lh6mfv2j.fsf@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: "Aneesh Kumar K.V" , benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, akpm@linux-foundation.org, Mel Gorman , "Kirill A. Shutemov" Cc: linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org > Now we can't depend for mm_cpumask, a parallel find_linux_pte_hugepte > can happen outside that. Now i had a variant for kick_all_cpus_sync that > ignored idle cpus. But then that needs more verification. > > http://article.gmane.org/gmane.linux.ports.ppc.embedded/81105 Can be racy as a CPU moves from non-idle to idle In > +A A A A A pmd_hugepage_update(vma->vm_mm, address, pmdp, ~0UL, 0); > +A A A A A /* > +A A A A A A * This ensures that generic code that rely on IRQ disabling > +A A A A A A * to prevent a parallel THP split work as expected. > +A A A A A A */ > +A A A A A kick_all_cpus_sync(); pmdp_invalidate()->pmd_hugepage_update() can still run in parallel withA find_linux_pte_or_hugepte() and race.. Am I missing something? Balbir Singh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org