1 /*
   2  * Copyright (c) 2001, 2013, 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.hpp"
  27 #ifdef TARGET_OS_FAMILY_linux
  28 # include "os_linux.inline.hpp"
  29 #endif
  30 #ifdef TARGET_OS_FAMILY_solaris
  31 # include "os_solaris.inline.hpp"
  32 #endif
  33 #ifdef TARGET_OS_FAMILY_windows
  34 # include "os_windows.inline.hpp"
  35 #endif
  36 #ifdef TARGET_OS_FAMILY_aix
  37 # include "os_aix.inline.hpp"
  38 #endif
  39 #ifdef TARGET_OS_FAMILY_bsd
  40 # include "os_bsd.inline.hpp"
  41 #endif
  42 
  43 #include "runtime/atomic.inline.hpp"
  44 
  45 jbyte Atomic::cmpxchg(jbyte exchange_value, volatile jbyte* dest, jbyte compare_value) {
  46   assert(sizeof(jbyte) == 1, "assumption.");
  47   uintptr_t dest_addr = (uintptr_t)dest;
  48   uintptr_t offset = dest_addr % sizeof(jint);
  49   volatile jint* dest_int = (volatile jint*)(dest_addr - offset);
  50   jint cur = *dest_int;
  51   jbyte* cur_as_bytes = (jbyte*)(&cur);
  52   jint new_val = cur;
  53   jbyte* new_val_as_bytes = (jbyte*)(&new_val);
  54   new_val_as_bytes[offset] = exchange_value;
  55   while (cur_as_bytes[offset] == compare_value) {
  56     jint res = cmpxchg(new_val, dest_int, cur);
  57     if (res == cur) break;
  58     cur = res;
  59     new_val = cur;
  60     new_val_as_bytes[offset] = exchange_value;
  61   }
  62   return cur_as_bytes[offset];
  63 }
  64 
  65 unsigned Atomic::xchg(unsigned int exchange_value, volatile unsigned int* dest) {
  66   assert(sizeof(unsigned int) == sizeof(jint), "more work to do");
  67   return (unsigned int)Atomic::xchg((jint)exchange_value, (volatile jint*)dest);
  68 }
  69 
  70 unsigned Atomic::cmpxchg(unsigned int exchange_value,
  71                          volatile unsigned int* dest, unsigned int compare_value) {
  72   assert(sizeof(unsigned int) == sizeof(jint), "more work to do");
  73   return (unsigned int)Atomic::cmpxchg((jint)exchange_value, (volatile jint*)dest,
  74                                        (jint)compare_value);
  75 }
  76 
  77 jlong Atomic::add(jlong    add_value, volatile jlong*    dest) {
  78   jlong old = load(dest);
  79   jlong new_value = old + add_value;
  80   while (old != cmpxchg(new_value, dest, old)) {
  81     old = load(dest);
  82     new_value = old + add_value;
  83   }
  84   return old;
  85 }
  86 
  87 void Atomic::inc(volatile short* dest) {
  88   // Most platforms do not support atomic increment on a 2-byte value. However,
  89   // if the value occupies the most significant 16 bits of an aligned 32-bit
  90   // word, then we can do this with an atomic add of 0x10000 to the 32-bit word.
  91   //
  92   // The least significant parts of this 32-bit word will never be affected, even
  93   // in case of overflow/underflow.
  94   //
  95   // Use the ATOMIC_SHORT_PAIR macro to get the desired alignment.
  96 #ifdef VM_LITTLE_ENDIAN
  97   assert((intx(dest) & 0x03) == 0x02, "wrong alignment");
  98   (void)Atomic::add(0x10000, (volatile int*)(dest-1));
  99 #else
 100   assert((intx(dest) & 0x03) == 0x00, "wrong alignment");
 101   (void)Atomic::add(0x10000, (volatile int*)(dest));
 102 #endif
 103 }
 104 
 105 void Atomic::dec(volatile short* dest) {
 106 #ifdef VM_LITTLE_ENDIAN
 107   assert((intx(dest) & 0x03) == 0x02, "wrong alignment");
 108   (void)Atomic::add(-0x10000, (volatile int*)(dest-1));
 109 #else
 110   assert((intx(dest) & 0x03) == 0x00, "wrong alignment");
 111   (void)Atomic::add(-0x10000, (volatile int*)(dest));
 112 #endif
 113 }
 114