From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751584AbdEASdx (ORCPT ); Mon, 1 May 2017 14:33:53 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:34814 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751041AbdEASds (ORCPT ); Mon, 1 May 2017 14:33:48 -0400 Subject: Re: [PATCH man-pages 4/5] userfaultfd.2: add note about asynchronios events delivery To: Mike Rapoport References: <1493617399-20897-1-git-send-email-rppt@linux.vnet.ibm.com> <1493617399-20897-5-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: <5fb9e169-5d92-2fe8-cc59-5c68cfb6be72@gmail.com> Date: Mon, 1 May 2017 20:33:45 +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: <1493617399-20897-5-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 Hi Mike, On 05/01/2017 07:43 AM, Mike Rapoport wrote: > Signed-off-by: Mike Rapoport Thanks. Applied. One question below. > --- > man2/userfaultfd.2 | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 > index 8b89162..f177bba 100644 > --- a/man2/userfaultfd.2 > +++ b/man2/userfaultfd.2 > @@ -112,6 +112,18 @@ created for the child process, > which allows userfaultfd monitor to perform user-space paging > for the child process. > > +Unlike page faults which have to be synchronous and require > +explicit or implicit wakeup, > +all other events are delivered asynchronously and > +the non-cooperative process resumes execution as > +soon as manager executes > +.BR read(2). > +The userfaultfd manager should carefully synchronize calls > +to UFFDIO_COPY with the events processing. > + > +The current asynchronous model of the event delivery is optimal for > +single threaded non-cooperative userfaultfd manager implementations. The preceding paragraph feels incomplete. It seems like you want to make a point with that last sentence, but the point is not explicit. What's missing? > + > .\" FIXME elaborate about non-cooperating mode, describe its limitations > .\" for kernels before 4.11, features added in 4.11 > .\" and limitations remaining in 4.11 > Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/