1 /* 2 * Copyright (c) 2001, 2014, 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.inline.hpp" 27 28 /* 29 * This is the default implementation of byte-sized cmpxchg. It emulates jbyte-sized cmpxchg 30 * in terms of jint-sized cmpxchg. Platforms may override this by defining their own inline definition 31 * in their AtomicPlatform class. 32 */ 33 jbyte AtomicBase::cmpxchg_general(jbyte exchange_value, volatile jbyte* dest, jbyte compare_value) { 34 assert(sizeof(jbyte) == 1, "assumption."); 35 uintptr_t dest_addr = (uintptr_t)dest; 36 uintptr_t offset = dest_addr % sizeof(jint); 37 volatile jint* dest_int = (volatile jint*)(dest_addr - offset); 38 jint cur = *dest_int; 39 jbyte* cur_as_bytes = (jbyte*)(&cur); 40 jint new_val = cur; 41 jbyte* new_val_as_bytes = (jbyte*)(&new_val); 42 new_val_as_bytes[offset] = exchange_value; 43 while (cur_as_bytes[offset] == compare_value) { 44 jint res = Atomic::cmpxchg(new_val, dest_int, cur); 45 if (res == cur) break; 46 cur = res; 47 new_val = cur; 48 new_val_as_bytes[offset] = exchange_value; 49 } 50 return cur_as_bytes[offset]; 51 } 52 53 unsigned Atomic::xchg(unsigned int exchange_value, volatile unsigned int* dest) { 54 assert(sizeof(unsigned int) == sizeof(jint), "more work to do"); 55 return (unsigned int)Atomic::xchg((jint)exchange_value, (volatile jint*)dest); 56 } 57 58 unsigned Atomic::cmpxchg(unsigned int exchange_value, 59 volatile unsigned int* dest, unsigned int compare_value) { 60 assert(sizeof(unsigned int) == sizeof(jint), "more work to do"); 61 return (unsigned int)Atomic::cmpxchg((jint)exchange_value, (volatile jint*)dest, 62 (jint)compare_value); 63 } 64 65 jlong Atomic::add(jlong add_value, volatile jlong* dest) { 66 jlong old = load(dest); 67 jlong new_value = old + add_value; 68 while (old != cmpxchg(new_value, dest, old)) { 69 old = load(dest); 70 new_value = old + add_value; 71 } 72 return old; 73 } 74 75 void Atomic::inc(volatile short* dest) { 76 // Most platforms do not support atomic increment on a 2-byte value. However, 77 // if the value occupies the most significant 16 bits of an aligned 32-bit 78 // word, then we can do this with an atomic add of 0x10000 to the 32-bit word. 79 // 80 // The least significant parts of this 32-bit word will never be affected, even 81 // in case of overflow/underflow. 82 // 83 // Use the ATOMIC_SHORT_PAIR macro to get the desired alignment. 84 #ifdef VM_LITTLE_ENDIAN 85 assert((intx(dest) & 0x03) == 0x02, "wrong alignment"); 86 (void)Atomic::add(0x10000, (volatile int*)(dest-1)); 87 #else 88 assert((intx(dest) & 0x03) == 0x00, "wrong alignment"); 89 (void)Atomic::add(0x10000, (volatile int*)(dest)); 90 #endif 91 } 92 93 void Atomic::dec(volatile short* dest) { 94 #ifdef VM_LITTLE_ENDIAN 95 assert((intx(dest) & 0x03) == 0x02, "wrong alignment"); 96 (void)Atomic::add(-0x10000, (volatile int*)(dest-1)); 97 #else 98 assert((intx(dest) & 0x03) == 0x00, "wrong alignment"); 99 (void)Atomic::add(-0x10000, (volatile int*)(dest)); 100 #endif 101 } 102