From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S376221AbdEAFoH (ORCPT ); Mon, 1 May 2017 01:44:07 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:42046 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S642677AbdEAFni (ORCPT ); Mon, 1 May 2017 01:43:38 -0400 From: Mike Rapoport To: "Michael Kerrisk (man-pages)" Cc: Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-man@vger.kernel.org, Mike Rapoport Subject: [PATCH man-pages 4/5] userfaultfd.2: add note about asynchronios events delivery Date: Mon, 1 May 2017 08:43:18 +0300 X-Mailer: git-send-email 1.9.1 In-Reply-To: <1493617399-20897-1-git-send-email-rppt@linux.vnet.ibm.com> References: <1493617399-20897-1-git-send-email-rppt@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17050105-0016-0000-0000-0000048D4740 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17050105-0017-0000-0000-000027777367 Message-Id: <1493617399-20897-5-git-send-email-rppt@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-05-01_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1705010035 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Mike Rapoport --- 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. + .\" 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 -- 1.9.1