atomic.hpp revision 5776:de6a9e811145 
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24
25#ifndef SHARE_VM_RUNTIME_ATOMIC_HPP
26#define SHARE_VM_RUNTIME_ATOMIC_HPP
27
28#include "memory/allocation.hpp"
29
30class 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_ptr(intptr_t store_value, intptr_t* dest);
45  inline static void store_ptr(void*    store_value, void*     dest);
46
47  inline static void store    (jbyte    store_value, volatile jbyte*    dest);
48  inline static void store    (jshort   store_value, volatile jshort*   dest);
49  inline static void store    (jint     store_value, volatile jint*     dest);
50  // See comment above about using jlong atomics on 32-bit platforms
51  inline static void store    (jlong    store_value, volatile jlong*    dest);
52  inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest);
53  inline static void store_ptr(void*    store_value, volatile void*     dest);
54
55  // See comment above about using jlong atomics on 32-bit platforms
56  inline static jlong load(volatile jlong* src);
57
58  // Atomically add to a location, return updated value
59  inline static jint     add    (jint     add_value, volatile jint*     dest);
60  inline static intptr_t add_ptr(intptr_t add_value, volatile intptr_t* dest);
61  inline static void*    add_ptr(intptr_t add_value, volatile void*     dest);
62  // See comment above about using jlong atomics on 32-bit platforms
63         static jlong    add    (jlong    add_value, volatile jlong*    dest);
64
65  // Atomically increment location
66  inline static void inc    (volatile jint*     dest);
67         static void inc    (volatile jshort*   dest);
68  inline static void inc_ptr(volatile intptr_t* dest);
69  inline static void inc_ptr(volatile void*     dest);
70
71  // Atomically decrement a location
72  inline static void dec    (volatile jint*     dest);
73         static void dec    (volatile jshort*    dest);
74  inline static void dec_ptr(volatile intptr_t* dest);
75  inline static void dec_ptr(volatile void*     dest);
76
77  // Performs atomic exchange of *dest with exchange_value.  Returns old prior value of *dest.
78  inline static jint         xchg(jint         exchange_value, volatile jint*         dest);
79         static unsigned int xchg(unsigned int exchange_value, volatile unsigned int* dest);
80
81  inline static intptr_t xchg_ptr(intptr_t exchange_value, volatile intptr_t* dest);
82  inline static void*    xchg_ptr(void*    exchange_value, volatile void*   dest);
83
84  // Performs atomic compare of *dest and compare_value, and exchanges *dest with exchange_value
85  // if the comparison succeeded.  Returns prior value of *dest.  Guarantees a two-way memory
86  // barrier across the cmpxchg.  I.e., it's really a 'fence_cmpxchg_acquire'.
87         static jbyte    cmpxchg    (jbyte    exchange_value, volatile jbyte*    dest, jbyte    compare_value);
88  inline static jint     cmpxchg    (jint     exchange_value, volatile jint*     dest, jint     compare_value);
89  // See comment above about using jlong atomics on 32-bit platforms
90  inline static jlong    cmpxchg    (jlong    exchange_value, volatile jlong*    dest, jlong    compare_value);
91
92         static unsigned int cmpxchg(unsigned int exchange_value,
93                                     volatile unsigned int* dest,
94                                     unsigned int compare_value);
95
96  inline static intptr_t cmpxchg_ptr(intptr_t exchange_value, volatile intptr_t* dest, intptr_t compare_value);
97  inline static void*    cmpxchg_ptr(void*    exchange_value, volatile void*     dest, void*    compare_value);
98};
99
100// To use Atomic::inc(jshort* dest) and Atomic::dec(jshort* dest), the address must be specially
101// aligned, such that (*dest) occupies the upper 16 bits of an aligned 32-bit word. The best way to
102// achieve is to place your short value next to another short value, which doesn't need atomic ops.
103//
104// Example
105//  ATOMIC_SHORT_PAIR(
106//    volatile short _refcount,  // needs atomic operation
107//    unsigned short _length     // number of UTF8 characters in the symbol (does not need atomic op)
108//  );
109
110#ifdef VM_LITTLE_ENDIAN
111#define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \
112    non_atomic_decl; \
113    atomic_decl
114#else
115#define ATOMIC_SHORT_PAIR(atomic_decl, non_atomic_decl) \
116    atomic_decl ; \
117    non_atomic_decl
118#endif
119
120#endif // SHARE_VM_RUNTIME_ATOMIC_HPP
121