1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
|
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
using System;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;
using System.Runtime.ConstrainedExecution;
using System.Runtime.CompilerServices;
using System.Runtime;
using System.Security;
namespace System.Threading
{
//
// Methods for accessing memory with volatile semantics. These are preferred over Thread.VolatileRead
// and Thread.VolatileWrite, as these are implemented more efficiently.
//
// (We cannot change the implementations of Thread.VolatileRead/VolatileWrite without breaking code
// that relies on their overly-strong ordering guarantees.)
//
// The actual implementations of these methods are typically supplied by the VM at JIT-time, because C# does
// not allow us to express a volatile read/write from/to a byref arg.
// See getILIntrinsicImplementationForVolatile() in jitinterface.cpp.
//
public static class Volatile
{
[System.Runtime.Versioning.NonVersionable]
public static bool Read(ref bool location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static sbyte Read(ref sbyte location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[System.Runtime.Versioning.NonVersionable]
public static byte Read(ref byte location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[System.Runtime.Versioning.NonVersionable]
public static short Read(ref short location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static ushort Read(ref ushort location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[System.Runtime.Versioning.NonVersionable]
public static int Read(ref int location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static uint Read(ref uint location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
#if BIT64
[System.Runtime.Versioning.NonVersionable]
public static long Read(ref long location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static ulong Read(ref ulong location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
#else
public static long Read(ref long location)
{
//
// On 32-bit machines, we use this implementation, since an ordinary volatile read
// would not be atomic.
//
// On 64-bit machines, the VM will replace this with a more efficient implementation.
//
return Interlocked.CompareExchange(ref location, 0, 0);
}
[CLSCompliant(false)]
public static ulong Read(ref ulong location)
{
unsafe
{
//
// There is no overload of Interlocked.Exchange that accepts a ulong. So we have
// to do some pointer tricks to pass our arguments to the overload that takes a long.
//
fixed (ulong* pLocation = &location)
{
return (ulong)Interlocked.CompareExchange(ref *(long*)pLocation, 0, 0);
}
}
}
#endif
[System.Runtime.Versioning.NonVersionable]
public static IntPtr Read(ref IntPtr location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static UIntPtr Read(ref UIntPtr location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[System.Runtime.Versioning.NonVersionable]
public static float Read(ref float location)
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[System.Runtime.Versioning.NonVersionable]
public static double Read(ref double location)
{
//
// On 32-bit machines, we use this implementation, since an ordinary volatile read
// would not be atomic.
//
// On 64-bit machines, the VM will replace this with a more efficient implementation.
//
return Interlocked.CompareExchange(ref location, 0, 0);
}
[System.Runtime.Versioning.NonVersionable]
public static T Read<T>(ref T location) where T : class
{
//
// The VM will replace this with a more efficient implementation.
//
var value = location;
Thread.MemoryBarrier();
return value;
}
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref bool location, bool value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref sbyte location, sbyte value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref byte location, byte value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref short location, short value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref ushort location, ushort value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref int location, int value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref uint location, uint value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
#if BIT64
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref long location, long value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref ulong location, ulong value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
#else
public static void Write(ref long location, long value)
{
//
// On 32-bit machines, we use this implementation, since an ordinary volatile write
// would not be atomic.
//
// On 64-bit machines, the VM will replace this with a more efficient implementation.
//
Interlocked.Exchange(ref location, value);
}
[CLSCompliant(false)]
public static void Write(ref ulong location, ulong value)
{
//
// On 32-bit machines, we use this implementation, since an ordinary volatile write
// would not be atomic.
//
// On 64-bit machines, the VM will replace this with a more efficient implementation.
//
unsafe
{
//
// There is no overload of Interlocked.Exchange that accepts a ulong. So we have
// to do some pointer tricks to pass our arguments to the overload that takes a long.
//
fixed (ulong* pLocation = &location)
{
Interlocked.Exchange(ref *(long*)pLocation, (long)value);
}
}
}
#endif
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref IntPtr location, IntPtr value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[CLSCompliant(false)]
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref UIntPtr location, UIntPtr value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref float location, float value)
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
[System.Runtime.Versioning.NonVersionable]
public static void Write(ref double location, double value)
{
//
// On 32-bit machines, we use this implementation, since an ordinary volatile write
// would not be atomic.
//
// On 64-bit machines, the VM will replace this with a more efficient implementation.
//
Interlocked.Exchange(ref location, value);
}
[System.Runtime.Versioning.NonVersionable]
public static void Write<T>(ref T location, T value) where T : class
{
//
// The VM will replace this with a more efficient implementation.
//
Thread.MemoryBarrier();
location = value;
}
}
}
|
