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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
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