1 /* 2 * Copyright (c) 2019, 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 #ifndef SHARE_GC_G1_G1FREEIDSET_HPP 26 #define SHARE_GC_G1_G1FREEIDSET_HPP 27 28 #include "runtime/semaphore.hpp" 29 #include "utilities/globalDefinitions.hpp" 30 31 // Represents a set of small integer ids, from which elements can be 32 // temporarily allocated for exclusive use. The ids are in a 33 // contiguous range from 'start' to 'start + size'. Used to obtain a 34 // distinct worker_id value for a mutator thread that doesn't normally 35 // have such an id. 36 class G1FreeIdSet { 37 Semaphore _sem; 38 uint* _next; 39 uint _start; 40 uint _size; 41 uintx _head_index_mask; 42 volatile uintx _head; 43 44 uint head_index(uintx head) const; 45 uintx make_head(uint index, uintx old_head) const; 46 47 NONCOPYABLE(G1FreeIdSet); 48 49 public: 50 G1FreeIdSet(uint start, uint size); 51 ~G1FreeIdSet(); 52 53 // Returns an unclaimed parallel id (waiting for one to be released if 54 // necessary). Must not safepoint while holding a claimed id. 55 uint claim_par_id(); 56 57 void release_par_id(uint id); 58 59 struct TestSupport; // For unit test access. 60 }; 61 62 #endif // SHARE_GC_G1_G1FREEIDSET_HPP 63