From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id 377006B0038 for ; Fri, 8 May 2015 18:21:52 -0400 (EDT) Received: by pabsx10 with SMTP id sx10so60419394pab.3 for ; Fri, 08 May 2015 15:21:51 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id sn2si8713009pac.206.2015.05.08.15.21.51 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 May 2015 15:21:51 -0700 (PDT) Date: Fri, 8 May 2015 15:21:49 -0700 From: Andrew Morton Subject: Re: [PATCH V2 2/2] powerpc/thp: Serialize pmd clear against a linux page table walk. Message-Id: <20150508152149.7fd52bb4b7c2a0911c33be00@linux-foundation.org> In-Reply-To: <1430983408-24924-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> References: <1430983408-24924-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1430983408-24924-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Aneesh Kumar K.V" Cc: mpe@ellerman.id.au, paulus@samba.org, benh@kernel.crashing.org, kirill.shutemov@linux.intel.com, aarcange@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org On Thu, 7 May 2015 12:53:28 +0530 "Aneesh Kumar K.V" wrote: > Serialize against find_linux_pte_or_hugepte which does lock-less > lookup in page tables with local interrupts disabled. For huge pages > it casts pmd_t to pte_t. Since format of pte_t is different from > pmd_t we want to prevent transit from pmd pointing to page table > to pmd pointing to huge page (and back) while interrupts are disabled. > We clear pmd to possibly replace it with page table pointer in > different code paths. So make sure we wait for the parallel > find_linux_pte_or_hugepage to finish. I'm not seeing here any description of the problem which is being fixed. Does the patch make the machine faster? Does the machine crash? -- 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