1 /* 2 * Copyright (c) 1999, 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 #ifndef SHARE_VM_RUNTIME_ATOMIC_HPP 26 #define SHARE_VM_RUNTIME_ATOMIC_HPP 27 28 #include "memory/allocation.hpp" 29 30 typedef enum cmpxchg_cmpxchg_memory_order { 31 memory_order_relaxed, 32 // Use value which doesn't interfere with C++2011. We need to be more conservative. 33 memory_order_conservative = 8 34 } cmpxchg_memory_order; 35 36 class Atomic : AllStatic { 37 private: 38 static jbyte cmpxchg_general(jbyte exchange_value, volatile jbyte* dest, jbyte compare_value); 39 40 public: 41 // Atomic operations on jlong types are not available on all 32-bit 42 // platforms. If atomic ops on jlongs are defined here they must only 43 // be used from code that verifies they are available at runtime and 44 // can provide an alternative action if not - see supports_cx8() for 45 // a means to test availability. 46 47 // The memory operations that are mentioned with each of the atomic 48 // function families come from src/share/vm/runtime/orderAccess.hpp, 49 // e.g., <fence> is described in that file and is implemented by the 50 // OrderAccess::fence() function. See that file for the gory details 51 // on the Memory Access Ordering Model. 52 53 // All of the atomic operations that imply a read-modify-write action 54 // guarantee a two-way memory barrier across that operation. Historically 55 // these semantics reflect the strength of atomic operations that are 56 // provided on SPARC/X86. We assume that strength is necessary unless 57 // we can prove that a weaker form is sufficiently safe. 58 59 // Atomically store to a location 60 inline static void store (jbyte store_value, jbyte* dest); 61 inline static void store (jshort store_value, jshort* dest); 62 inline static void store (jint store_value, jint* dest); 63 // See comment above about using jlong atomics on 32-bit platforms 64 inline static void store (jlong store_value, jlong* dest); 65 inline static void store_ptr(intptr_t store_value, intptr_t* dest); 66 inline static void store_ptr(void* store_value, void* dest); 67 68 inline static void store (jbyte store_value, volatile jbyte* dest); 69 inline static void store (jshort store_value, volatile jshort* dest); 70 inline static void store (jint store_value, volatile jint* dest); 71 // See comment above about using jlong atomics on 32-bit platforms 72 inline static void store (jlong store_value, volatile jlong* dest); 73 inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest); 74 inline static void store_ptr(void* store_value, volatile void* dest); 75 76 // See comment above about using jlong atomics on 32-bit platforms 77 inline static jlong load(volatile jlong* src); 78 79 // Atomically add to a location. Returns updated value. add*() provide: 80 // <fence> add-value-to-dest <membar StoreLoad|StoreStore> 81 inline static jint add (jint add_value, volatile jint* dest); 82 inline static size_t add (size_t add_value, volatile size_t* dest); 83 inline static intptr_t add_ptr(intptr_t add_value, volatile intptr_t* dest); 84 inline static void* add_ptr(intptr_t add_value, volatile void* dest); 85 // See comment above about using jlong atomics on 32-bit platforms 86 static jlong add (jlong add_value, volatile jlong* dest); 87 88 // Atomically increment location. inc*() provide: 89 // <fence> increment-dest <membar StoreLoad|StoreStore> 90 inline static void inc (volatile jint* dest); 91 static void inc (volatile jshort* dest); 92 inline static void inc (volatile size_t* dest); 93 inline static void inc_ptr(volatile intptr_t* dest); 94 inline static void inc_ptr(volatile void* dest); 95 96 // Atomically decrement a location. dec*() provide: 97 // <fence> decrement-dest <membar StoreLoad|StoreStore> 98 inline static void dec (volatile jint* dest); 99 static void dec (volatile jshort* dest); 100 inline static void dec (volatile size_t* dest); 101 inline static void dec_ptr(volatile intptr_t* dest); 102 inline static void dec_ptr(volatile void* dest); 103 104 // Performs atomic exchange of *dest with exchange_value. Returns old 105 // prior value of *dest. xchg*() provide: 106 // <fence> exchange-value-with-dest <membar StoreLoad|StoreStore> 107 inline static jint xchg (jint exchange_value, volatile jint* dest); 108 static unsigned int xchg (unsigned int exchange_value, volatile unsigned int* dest); 109 inline static intptr_t xchg_ptr(intptr_t exchange_value, volatile intptr_t* dest); 110 inline static void* xchg_ptr(void* exchange_value, volatile void* dest); 111 112 // Performs atomic compare of *dest and compare_value, and exchanges 113 // *dest with exchange_value if the comparison succeeded. Returns prior 114 // value of *dest. cmpxchg*() provide: 115 // <fence> compare-and-exchange <membar StoreLoad|StoreStore> 116 inline static jbyte cmpxchg (jbyte exchange_value, volatile jbyte* dest, jbyte compare_value, cmpxchg_memory_order order = memory_order_conservative); 117 inline static jint cmpxchg (jint exchange_value, volatile jint* dest, jint compare_value, cmpxchg_memory_order order = memory_order_conservative); 118 // See comment above about using jlong atomics on 32-bit platforms 119 inline static jlong cmpxchg (jlong exchange_value, volatile jlong* dest, jlong compare_value, cmpxchg_memory_order order = memory_order_conservative); 120 static unsigned int cmpxchg (unsigned int exchange_value, volatile unsigned int* dest, unsigned int compare_value, cmpxchg_memory_order order = memory_order_conservative); 121 inline static intptr_t cmpxchg_ptr(intptr_t exchange_value, volatile intptr_t* dest, intptr_t compare_value, cmpxchg_memory_order order = memory_order_conservative); 122 inline static void* cmpxchg_ptr(void* exchange_value, volatile void* dest, void* compare_value, cmpxchg_memory_order order = memory_order_conservative); 123 }; 124 125 // To use Atomic::inc(jshort* dest) and Atomic::dec(jshort* dest), the address must be specially 126 // aligned, such that (*dest) occupies the upper 16 bits of an aligned 32-bit word. The best way to 127 // achieve is to place your short value next to another short value, which doesn't need atomic ops. 128 // 129 // Example 130 // ATOMIC_SHORT_PAIR( 131 // volatile short _refcount, // needs atomic operation 132 // unsigned short _length // number of UTF8 characters in the symbol (does not need atomic op) 133 // ); 134 135 #ifdef VM_LITTLE_ENDIAN 136 #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \ 137 non_atomic_decl; \ 138 atomic_decl 139 #else 140 #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \ 141 atomic_decl; \ 142 non_atomic_decl 143 #endif 144 145 #endif // SHARE_VM_RUNTIME_ATOMIC_HPP