linux-kernel - [PATCH man-pages 4/5] userfaultfd.2: add note about asynchronios events delivery

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Message-Id: <1493617399-20897-5-git-send-email-rppt@linux.vnet.ibm.com>
Date:   Mon,  1 May 2017 08:43:18 +0300
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Cc:     Andrea Arcangeli <aarcange@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-man@...r.kernel.org, Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: [PATCH man-pages 4/5] userfaultfd.2: add note about asynchronios events delivery

Signed-off-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
---
 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