Add __safe_fatal and use it in __pthread_unwind forwarder fallback.

sysdeps/generic/safe-fatal.h

@@ -0,0 +1,37 @@
+/* Crash the process immediately, without possibility of deadlock.  Generic.
+   Copyright (C) 2014 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/>.  */
+
+#ifndef _SAFE_FATAL_H
+#define _SAFE_FATAL_H   1
+
+#include <abort-instr.h>
+
+static inline void
+__safe_fatal (void)
+{
+#ifdef ABORT_INSTRUCTION
+  /* This is not guaranteed to be free from the possibility of deadlock,
+     since it might generate a signal that can be caught.  But it's better
+     than nothing.  */
+  ABORT_INSTRUCTION;
+#else
+# error Need an OS-specific or machine-specific safe-fatal.h
+#endif
+}
+
+#endif  /* safe-fatal.h */