Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1954923AbdDZHS0 (ORCPT ); Wed, 26 Apr 2017 03:18:26 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:35608 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1952751AbdDZHSR (ORCPT ); Wed, 26 Apr 2017 03:18:17 -0400 Subject: Re: [PATCH 5/5] usefaultfd.2: add brief description of "non-cooperative" mode To: Mike Rapoport References: <1493137748-32452-1-git-send-email-rppt@linux.vnet.ibm.com> <1493137748-32452-6-git-send-email-rppt@linux.vnet.ibm.com> Cc: mtk.manpages@gmail.com, Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-man@vger.kernel.org From: "Michael Kerrisk (man-pages)" Message-ID: Date: Wed, 26 Apr 2017 09:18:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <1493137748-32452-6-git-send-email-rppt@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1597 Lines: 45 On 04/25/2017 06:29 PM, Mike Rapoport wrote: > Signed-off-by: Mike Rapoport Thanks, Mike. Applied. Cheers, Michael > --- > man2/userfaultfd.2 | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 > index dc37319..291dd10 100644 > --- a/man2/userfaultfd.2 > +++ b/man2/userfaultfd.2 > @@ -89,6 +89,20 @@ them using the operations described in > .BR ioctl_userfaultfd (2). > When servicing the page fault events, > the fault-handling thread can trigger a wake-up for the sleeping thread. > + > +It is possible for the faulting threads and the fault-handling threads > +to run in the context of different processes. > +In this case, these threads may belong to different programs, > +and the program that executes the faulting threads > +will not necessarily cooperate with the program that handles the page faults. > +In such non-cooperative mode, > +the process that monitors userfaultfd and handles page faults, > +needs to be aware of the changes in the virtual memory layout > +of the faulting process to avoid memory corruption. > +.\" FIXME elaborate about non-cooperating mode, describe its limitations > +.\" for kerneles before 4.11, features added in 4.11 > +.\" and limitations remaining in 4.11 > +.\" Maybe it's worth adding a dedicated sub-section... > .\" > .SS Userfaultfd operation > After the userfaultfd object is created with > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/