From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f43.google.com (mail-pb0-f43.google.com [209.85.160.43]) by kanga.kvack.org (Postfix) with ESMTP id 89EDB6B0037 for ; Tue, 4 Mar 2014 00:32:20 -0500 (EST) Received: by mail-pb0-f43.google.com with SMTP id um1so4745634pbc.2 for ; Mon, 03 Mar 2014 21:32:20 -0800 (PST) Received: from g4t3427.houston.hp.com (g4t3427.houston.hp.com. [15.201.208.55]) by mx.google.com with ESMTPS id po10si12904441pab.73.2014.03.03.21.32.18 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 03 Mar 2014 21:32:19 -0800 (PST) Message-ID: <1393911136.2512.1.camel@buesod1.americas.hpqcorp.net> Subject: Re: [PATCH v4] mm: per-thread vma caching From: Davidlohr Bueso Date: Mon, 03 Mar 2014 21:32:16 -0800 In-Reply-To: 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> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Andrew Morton , 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 Mon, 2014-03-03 at 19:26 -0800, 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. And: [ 4.274542] Call Trace: [ 4.274747] [] dump_stack+0x46/0x58 [ 4.275069] [] vmacache_find+0xae/0xc0 [ 4.275425] [] find_vma+0x20/0x80 [ 4.275625] [] find_extend_vma+0x2b/0x90 [ 4.275982] [] __get_user_pages+0x99/0x5a0 [ 4.276427] [] ? follow_page_mask+0x32b/0x400 [ 4.276671] [] get_user_pages+0x52/0x60 [ 4.276886] [] copy_strings.isra.20+0x1a3/0x2f0 [ 4.277239] [] copy_strings_kernel+0x3d/0x50 [ 4.277472] [] load_script+0x1e8/0x280 [ 4.277692] [] ? copy_strings.isra.20+0xea/0x2f0 [ 4.277931] [] search_binary_handler+0x97/0x1d0 [ 4.278288] [] do_execve_common.isra.28+0x4ef/0x650 [ 4.278544] [] do_execve+0x18/0x20 [ 4.278754] [] SyS_execve+0x2e/0x40 [ 4.278960] [] stub_execve+0x69/0xa0 -- 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