/* * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #ifndef SHARE_VM_RUNTIME_ATOMIC_HPP #define SHARE_VM_RUNTIME_ATOMIC_HPP #include "memory/allocation.hpp" typedef enum memory_order { memory_order_relaxed, memory_order_consume, memory_order_acquire, memory_order_release, memory_order_acq_rel, memory_order_seq_cst } memory_order; class Atomic : AllStatic { private: static jbyte cmpxchg_general(jbyte exchange_value, volatile jbyte* dest, jbyte compare_value); public: // Atomic operations on jlong types are not available on all 32-bit // platforms. If atomic ops on jlongs are defined here they must only // be used from code that verifies they are available at runtime and // can provide an alternative action if not - see supports_cx8() for // a means to test availability. // The memory operations that are mentioned with each of the atomic // function families come from src/share/vm/runtime/orderAccess.hpp, // e.g., is described in that file and is implemented by the // OrderAccess::fence() function. See that file for the gory details // on the Memory Access Ordering Model. // All of the atomic operations that imply a read-modify-write action // guarantee a two-way memory barrier across that operation. Historically // these semantics reflect the strength of atomic operations that are // provided on SPARC/X86. We assume that strength is necessary unless // we can prove that a weaker form is sufficiently safe. // Atomically store to a location inline static void store (jbyte store_value, jbyte* dest); inline static void store (jshort store_value, jshort* dest); inline static void store (jint store_value, jint* dest); // See comment above about using jlong atomics on 32-bit platforms inline static void store (jlong store_value, jlong* dest); inline static void store_ptr(intptr_t store_value, intptr_t* dest); inline static void store_ptr(void* store_value, void* dest); inline static void store (jbyte store_value, volatile jbyte* dest); inline static void store (jshort store_value, volatile jshort* dest); inline static void store (jint store_value, volatile jint* dest); // See comment above about using jlong atomics on 32-bit platforms inline static void store (jlong store_value, volatile jlong* dest); inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest); inline static void store_ptr(void* store_value, volatile void* dest); // See comment above about using jlong atomics on 32-bit platforms inline static jlong load(volatile jlong* src); // Atomically add to a location. Returns updated value. add*() provide: // add-value-to-dest inline static jint add (jint add_value, volatile jint* dest); inline static size_t add (size_t add_value, volatile size_t* dest); inline static intptr_t add_ptr(intptr_t add_value, volatile intptr_t* dest); inline static void* add_ptr(intptr_t add_value, volatile void* dest); // See comment above about using jlong atomics on 32-bit platforms static jlong add (jlong add_value, volatile jlong* dest); // Atomically increment location. inc*() provide: // increment-dest inline static void inc (volatile jint* dest); static void inc (volatile jshort* dest); inline static void inc (volatile size_t* dest); inline static void inc_ptr(volatile intptr_t* dest); inline static void inc_ptr(volatile void* dest); // Atomically decrement a location. dec*() provide: // decrement-dest inline static void dec (volatile jint* dest); static void dec (volatile jshort* dest); inline static void dec (volatile size_t* dest); inline static void dec_ptr(volatile intptr_t* dest); inline static void dec_ptr(volatile void* dest); // Performs atomic exchange of *dest with exchange_value. Returns old // prior value of *dest. xchg*() provide: // exchange-value-with-dest inline static jint xchg (jint exchange_value, volatile jint* dest); static unsigned int xchg (unsigned int exchange_value, volatile unsigned int* dest); inline static intptr_t xchg_ptr(intptr_t exchange_value, volatile intptr_t* dest); inline static void* xchg_ptr(void* exchange_value, volatile void* dest); // Performs atomic compare of *dest and compare_value, and exchanges // *dest with exchange_value if the comparison succeeded. Returns prior // value of *dest. cmpxchg*() provide: // compare-and-exchange inline static jbyte cmpxchg (jbyte exchange_value, volatile jbyte* dest, jbyte compare_value, memory_order order = memory_order_seq_cst); inline static jint cmpxchg (jint exchange_value, volatile jint* dest, jint compare_value, memory_order order = memory_order_seq_cst); // See comment above about using jlong atomics on 32-bit platforms inline static jlong cmpxchg (jlong exchange_value, volatile jlong* dest, jlong compare_value, memory_order order = memory_order_seq_cst); static unsigned int cmpxchg (unsigned int exchange_value, volatile unsigned int* dest, unsigned int compare_value, memory_order order = memory_order_seq_cst); inline static intptr_t cmpxchg_ptr(intptr_t exchange_value, volatile intptr_t* dest, intptr_t compare_value, memory_order order = memory_order_seq_cst); inline static void* cmpxchg_ptr(void* exchange_value, volatile void* dest, void* compare_value, memory_order order = memory_order_seq_cst); }; // To use Atomic::inc(jshort* dest) and Atomic::dec(jshort* dest), the address must be specially // aligned, such that (*dest) occupies the upper 16 bits of an aligned 32-bit word. The best way to // achieve is to place your short value next to another short value, which doesn't need atomic ops. // // Example // ATOMIC_SHORT_PAIR( // volatile short _refcount, // needs atomic operation // unsigned short _length // number of UTF8 characters in the symbol (does not need atomic op) // ); #ifdef VM_LITTLE_ENDIAN #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \ non_atomic_decl; \ atomic_decl #else #define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \ atomic_decl; \ non_atomic_decl #endif #endif // SHARE_VM_RUNTIME_ATOMIC_HPP