1 files changed, 44 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/hppa/nptl/pthread_spin_unlock.c b/REORG.TODO/sysdeps/hppa/nptl/pthread_spin_unlock.c
new file mode 100644
index 0000000000..7883568bc6
--- /dev/null
+++ b/REORG.TODO/sysdeps/hppa/nptl/pthread_spin_unlock.c
@@ -0,0 +1,44 @@
+/* Copyright (C) 2005-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "pthreadP.h"
+
+int
+pthread_spin_unlock (pthread_spinlock_t *lock)
+{
+  /* CONCURRENCTY NOTES:
+
+     The atomic_exchange_rel synchronizes-with the atomic_exhange_acq in
+     pthread_spin_lock.
+
+     On hppa we must not use a plain `stw` to reset the guard lock.  This
+     has to do with the kernel compare-and-swap helper that is used to
+     implement all of the atomic operations.
+
+     The kernel CAS helper uses its own internal locks and that means that
+     to create a true happens-before relationship between any two threads,
+     the second thread must observe the internal lock having a value of 0
+     (it must attempt to take the lock with ldcw).  This creates the
+     ordering required for a second thread to observe the effects of the
+     RMW of the kernel CAS helper in any other thread.
+
+     Therefore if a variable is used in an atomic macro it must always be
+     manipulated with atomic macros in order for memory ordering rules to
+     be preserved.  */
+  atomic_exchange_rel (lock, 0);
+  return 0;
+}