From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f41.google.com (mail-pa0-f41.google.com [209.85.220.41]) by kanga.kvack.org (Postfix) with ESMTP id D0EAB6B0035 for ; Fri, 14 Mar 2014 00:41:32 -0400 (EDT) Received: by mail-pa0-f41.google.com with SMTP id fa1so2096203pad.14 for ; Thu, 13 Mar 2014 21:41:32 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id a8si4302246pbs.87.2014.03.13.21.41.24 for ; Thu, 13 Mar 2014 21:41:24 -0700 (PDT) Date: Thu, 13 Mar 2014 21:43:08 -0700 From: Andrew Morton Subject: Re: [PATCH v4] mm: per-thread vma caching Message-Id: <20140313214308.090d1a18.akpm@linux-foundation.org> In-Reply-To: <5322720F.1030706@huawei.com> References: <1393537704.2899.3.camel@buesod1.americas.hpqcorp.net> <20140303164002.02df915e12d05bb98762407f@linux-foundation.org> <1393894778.30648.29.camel@buesod1.americas.hpqcorp.net> <20140303172348.3f00c9df.akpm@linux-foundation.org> <1393900953.30648.32.camel@buesod1.americas.hpqcorp.net> <20140303191224.96f93142.akpm@linux-foundation.org> <1393902810.30648.36.camel@buesod1.americas.hpqcorp.net> <5322720F.1030706@huawei.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: Li Zefan Cc: Davidlohr Bueso , Linus Torvalds , Ingo Molnar , Peter Zijlstra , Michel Lespinasse , Mel Gorman , Rik van Riel , KOSAKI Motohiro , "Chandramouleeswaran, Aswin" , "Norton, Scott J" , linux-mm , Linux Kernel Mailing List On Fri, 14 Mar 2014 11:05:51 +0800 Li Zefan wrote: > Hi Davidlohr, > > On 2014/3/4 11:26, Linus Torvalds wrote: > > On Mon, Mar 3, 2014 at 7:13 PM, Davidlohr Bueso wrote: > >> > >> Yes, I shortly realized that was silly... but I can say for sure it can > >> happen and a quick qemu run confirms it. So I see your point as to > >> asking why we need it, so now I'm looking for an explanation in the > >> code. > > > > We definitely *do* have users. > > > > One example would be ptrace -> access_process_vm -> __access_remote_vm > > -> get_user_pages() -> find_extend_vma() -> find_vma_prev -> find_vma. > > > > I raw this oops on 3.14.0-rc5-next-20140307, which is possible caused by > your patch? Don't know how it was triggered. > > ... > > [ 6072.027007] [] get_user_pages+0x52/0x60 > [ 6072.027015] [] __access_remote_vm+0x118/0x1f0 > [ 6072.027023] [] access_process_vm+0x5b/0x80 > [ 6072.027033] [] proc_pid_cmdline+0x77/0x120 > [ 6072.027041] [] proc_info_read+0xa2/0xe0 > [ 6072.027050] [] vfs_read+0xad/0x1a0 > [ 6072.027057] [] SyS_read+0x65/0xb0 > [ 6072.027066] [] system_call_fastpath+0x16/0x1b > [ 6072.027072] Code: f4 4c 89 f7 89 45 a4 e8 36 0e eb ff 48 3d 00 f0 ff ff 48 89 c3 0f 86 d7 00 00 00 4c 89 e0 > 49 8b 56 40 48 c1 e8 27 25 ff 01 00 00 <48> 8b 0c c2 48 85 c9 75 3e 41 83 e5 08 74 1b 49 8b 87 90 00 00 > [ 6072.027134] RIP [] follow_page_mask+0x69/0x620 > [ 6072.027142] RSP > [ 6072.027146] CR2: 00000000000007f8 Yep. Please grab whichever of mm-per-thread-vma-caching-fix-3.patch mm-per-thread-vma-caching-fix-4.patch mm-per-thread-vma-caching-fix-5.patch mm-per-thread-vma-caching-fix-6-checkpatch-fixes.patch mm-per-thread-vma-caching-fix-6-fix.patch which you don't have from http://ozlabs.org/~akpm/mmots/broken-out/ -- 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