Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

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;
+}