1 /*
 2  * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
 3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 4  *
 5  * This code is free software; you can redistribute it and/or modify it
 6  * under the terms of the GNU General Public License version 2 only, as
 7  * published by the Free Software Foundation.
 8  *
 9  * This code is distributed in the hope that it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12  * version 2 for more details (a copy is included in the LICENSE file that
13  * accompanied this code).
14  *
15  * You should have received a copy of the GNU General Public License version
16  * 2 along with this work; if not, write to the Free Software Foundation,
17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20  * or visit www.oracle.com if you need additional information or have any
21  * questions.
22  *
23  */
24 
25 #include "precompiled.hpp"
26 #include "runtime/atomic.hpp"
27 #include "runtime/threadIdentifier.hpp"
28 
29 static volatile int64_t next_thread_id = 2; // starting at 2, excluding the primordial thread id
30 
31 int64_t ThreadIdentifier::unsafe_offset() {
32   return reinterpret_cast<int64_t>(&next_thread_id);
33 }
34 
35 int64_t ThreadIdentifier::next() {
36   int64_t next_tid;
37   do {
38     next_tid = Atomic::load(&next_thread_id);
39   } while (Atomic::cmpxchg(&next_thread_id, next_tid, next_tid + 1) != next_tid);
40   return next_tid;
41 }