Build system: use SPDX identifiers

[urcu.git] / lgpl-relicensing.md

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+<!--
+SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+
+SPDX-License-Identifier: CC-BY-4.0
+-->
+
+# Userspace-RCU LGPL 2.1+ re-licensing
+
+Mathieu Desnoyers
+May 13th, 2009
+
+IBM Corporation allowed LGPLv2.1+ licensing of their contribution to the
+userspace RCU library in a patch submitted on May 8, 2009 from Paul E.
+McKenney and reviewed by Steven L. Bennett:
+
+    https://lists.lttng.org/pipermail/lttng-dev/2009-May/012835.html
+
+I (Mathieu Desnoyers) re-implemented ACCESS_ONCE(), likely(), unlikely() and
+barrier() from scratch without reference to the original code.
+
+    commit id : 2dc5fa0f7cfbfb0a64a7a67b39626650e863f16a
+
+Bert Wesarg <bert.wesarg@googlemail.com> approved LGPL re-licensing of his
+patch in an email dated May 13, 2009 :
+
+    http://lkml.org/lkml/2009/5/13/16
+
+xchg() primitives has been rewritten from a MIT-licensed cmpxchg for Intel
+and powerpc. They are MIT-licensed and therefore usable in LGPL code.
+This cmpxchg code was obtained from the atomic_ops project:
+
+    http://www.hpl.hp.com/research/linux/atomic_ops/
+
+I (Mathieu Desnoyers) wrote the remainder of the code.
+
+The license for the library files in this project was therefore changed to
+LGPLv2.1 on May 13, 2009, as detailed in LICENSE.