1 /* 2 * Copyright (c) 1999, 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_VM_RUNTIME_ATOMIC_HPP 26 #define SHARE_VM_RUNTIME_ATOMIC_HPP 27 28 #include "memory/allocation.hpp" 29 30 class Atomic : AllStatic { 31 public: 32 // Atomic operations on jlong types are not available on all 32-bit 33 // platforms. If atomic ops on jlongs are defined here they must only 34 // be used from code that verifies they are available at runtime and 35 // can provide an alternative action if not - see supports_cx8() for 36 // a means to test availability. 37 38 // Atomically store to a location 39 inline static void store (jbyte store_value, jbyte* dest); 40 inline static void store (jshort store_value, jshort* dest); 41 inline static void store (jint store_value, jint* dest); 42 // See comment above about using jlong atomics on 32-bit platforms 43 inline static void store (jlong store_value, jlong* dest); 44 inline static void store (julong store_value, julong* dest); 45 inline static void store_ptr(intptr_t store_value, intptr_t* dest); 46 inline static void store_ptr(void* store_value, void* dest); 47 48 inline static void store (jbyte store_value, volatile jbyte* dest); 49 inline static void store (jshort store_value, volatile jshort* dest); 50 inline static void store (jint store_value, volatile jint* dest); 51 // See comment above about using jlong atomics on 32-bit platforms 52 inline static void store (jlong store_value, volatile jlong* dest); 53 inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest); 54 inline static void store_ptr(void* store_value, volatile void* dest); 55 56 // See comment above about using jlong atomics on 32-bit platforms 57 inline static jlong load(volatile jlong* src); 58 static julong load(volatile julong* src); 59 60 // Atomically add to a location, return updated value 61 inline static jint add (jint add_value, volatile jint* dest); 62 inline static intptr_t add_ptr(intptr_t add_value, volatile intptr_t* dest); 63 inline static void* add_ptr(intptr_t add_value, volatile void* dest); 64 // See comment above about using jlong atomics on 32-bit platforms 65 static jlong add (jlong add_value, volatile jlong* dest); 66 static julong add (julong add_value, volatile julong* dest); 67 68 // Atomically increment location 69 inline static void inc (volatile jint* dest); 70 static void inc (volatile jshort* dest); 71 inline static void inc_ptr(volatile intptr_t* dest); 72 inline static void inc_ptr(volatile void* dest); 73 74 // Atomically decrement a location 75 inline static void dec (volatile jint* dest); 76 static void dec (volatile jshort* dest); 77 inline static void dec_ptr(volatile intptr_t* dest); 78 inline static void dec_ptr(volatile void* dest); 79 80 // Performs atomic exchange of *dest with exchange_value. Returns old prior value of *dest. 81 inline static jint xchg(jint exchange_value, volatile jint* dest); 82 static unsigned int xchg(unsigned int exchange_value, volatile unsigned int* dest); 83 84 inline static intptr_t xchg_ptr(intptr_t exchange_value, volatile intptr_t* dest); 85 inline static void* xchg_ptr(void* exchange_value, volatile void* dest); 86 87 // Performs atomic compare of *dest and compare_value, and exchanges *dest with exchange_value 88 // if the comparison succeeded. Returns prior value of *dest. Guarantees a two-way memory 89 // barrier across the cmpxchg. I.e., it's really a 'fence_cmpxchg_acquire'. 90 static jbyte cmpxchg (jbyte exchange_value, volatile jbyte* dest, jbyte compare_value); 91 inline static jint cmpxchg (jint exchange_value, volatile jint* dest, jint compare_value); 92 // See comment above about using jlong atomics on 32-bit platforms 93 inline static jlong cmpxchg (jlong exchange_value, volatile jlong* dest, jlong compare_value); 94 static julong cmpxchg (julong exchange_value, volatile julong* dest, julong compare_value); 95 96 static unsigned int cmpxchg(unsigned int exchange_value, 97 volatile unsigned int* dest, 98 unsigned int compare_value); 99 100 inline static intptr_t cmpxchg_ptr(intptr_t exchange_value, volatile intptr_t* dest, intptr_t compare_value); 101 inline static void* cmpxchg_ptr(void* exchange_value, volatile void* dest, void* compare_value); 102 }; 103 104 // To use Atomic::inc(jshort* dest) and Atomic::dec(jshort* dest), the address must be specially 105 // aligned, such that (*dest) occupies the upper 16 bits of an aligned 32-bit word. The best way to 106 // achieve is to place your short value next to another short value, which doesn't need atomic ops. 107 // 108 // Example 109 // ATOMIC_SHORT_PAIR( 110 // volatile short _refcount, // needs atomic operation 111 // unsigned short _length // number of UTF8 characters in the symbol (does not need atomic op) 112 // ); 113 114 #ifdef VM_LITTLE_ENDIAN 115 #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \ 116 non_atomic_decl; \ 117 atomic_decl 118 #else 119 #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \ 120 atomic_decl ; \ 121 non_atomic_decl 122 #endif 123 124 #endif // SHARE_VM_RUNTIME_ATOMIC_HPP