htl: Add futex-internal.h

That provides futex_supports_pshared

sysdeps/htl/futex-internal.h

@@ -0,0 +1,39 @@
+/* futex operations for glibc-internal use.  Stub version; do not include
+   this file directly.
+   Copyright (C) 2014-2020 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef STUB_FUTEX_INTERNAL_H
+#define STUB_FUTEX_INTERNAL_H
+
+#include <pthread.h>
+
+/* Returns EINVAL if PSHARED is neither PTHREAD_PROCESS_PRIVATE nor
+   PTHREAD_PROCESS_SHARED; otherwise, returns 0 if PSHARED is supported, and
+   ENOTSUP if not.  */
+static __always_inline int
+futex_supports_pshared (int pshared)
+{
+  if (__glibc_likely (pshared == PTHREAD_PROCESS_PRIVATE))
+    return 0;
+  else if (pshared == PTHREAD_PROCESS_SHARED)
+    return 0;
+  else
+    return EINVAL;
+}
+
+#endif  /* futex-internal.h */