Add release notes for pthread rwlocks change

diff --git a/doc/arm/notes-9.17.0.xml b/doc/arm/notes-9.17.0.xml
index 2b0de4afd704e7ead4f4dd1846c1807b28df9e3a..38eda27a790f339e79e2d6a724fae460b93f0f03 100644 (file)
--- a/doc/arm/notes-9.17.0.xml
+++ b/doc/arm/notes-9.17.0.xml
@@ -10,6 +10,20 @@
 -->
 
 <section xml:id="relnotes-9.17.0"><info><title>Notes for BIND 9.17.0</title></info>
+  <para>
+    System-provided pthread rwlocks implementation is used by default instead of
+    built-in ISC implementation of rwlocks. Please be aware that unpatched glibc
+    version from 2.26 had a <link xmlns:xlink="http://www.w3.org/1999/xlink"
+    xlink:href="https://sourceware.org/bugzilla/show_bug.cgi?id=23844">bug</link>
+    that could cause BIND 9 to deadlock.  The fix has been released as part of
+    glibc release 2.30, and various Linux distributions have patched their glibc
+    version with a notable exception of Ubuntu 18.04 (Bionic) which is work in
+    progress. If you are running on affected system (e.g. Ubuntu 18.04) you need
+    to compile BIND 9 with --disable-pthread-rwlock until Canonical releases
+    <link xmlns:xlink="http://www.w3.org/1999/xlink"
+    xlink:href="https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1864864">fixed
+    version</link>.
+  </para>
 
   <section xml:id="relnotes-9.17.0-changes"><info><title>Feature Changes</title></info>
     <itemizedlist>