[mirror_edk2.git] / MdePkg / Library / BaseLib / Synchronization.c

/** @file\r
  Implementation of synchronization functions.\r
\r
  Copyright (c) 2006, Intel Corporation<BR>\r
  All rights reserved. This program and the accompanying materials\r
  are licensed and made available under the terms and conditions of the BSD License\r
  which accompanies this distribution.  The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
\r
//\r
// Include common header file for this module.\r
//\r
\r
\r
#include "BaseLibInternals.h"\r
\r
#define SPIN_LOCK_RELEASED          ((UINTN) 1)\r
#define SPIN_LOCK_ACQUIRED          ((UINTN) 2)\r
\r
/**\r
  Retrieves the architecture specific spin lock alignment requirements for\r
  optimal spin lock performance.\r
\r
  This function retrieves the spin lock alignment requirements for optimal\r
  performance on a given CPU architecture. The spin lock alignment must be a\r
  power of two and is returned by this function. If there are no alignment\r
  requirements, then 1 must be returned. The spin lock synchronization\r
  functions must function correctly if the spin lock size and alignment values\r
  returned by this function are not used at all. These values are hints to the\r
  consumers of the spin lock synchronization functions to obtain optimal spin\r
  lock performance.\r
\r
  @return The architecture specific spin lock alignment.\r
\r
**/\r
UINTN\r
EFIAPI\r
GetSpinLockProperties (\r
  VOID\r
  )\r
{\r
  // @bug May use a PCD entry to determine this alignment.\r
  return 32;\r
}\r
\r
/**\r
  Initializes a spin lock to the released state and returns the spin lock.\r
\r
  This function initializes the spin lock specified by SpinLock to the released\r
  state, and returns SpinLock. Optimal performance can be achieved by calling\r
  GetSpinLockProperties() to determine the size and alignment requirements for\r
  SpinLock.\r
\r
  If SpinLock is NULL, then ASSERT().\r
\r
  @param  SpinLock  A pointer to the spin lock to initialize to the released\r
                    state.\r
\r
  @return SpinLock\r
\r
**/\r
SPIN_LOCK *\r
EFIAPI\r
InitializeSpinLock (\r
  OUT     SPIN_LOCK                 *SpinLock\r
  )\r
{\r
  ASSERT (SpinLock != NULL);\r
  *SpinLock = SPIN_LOCK_RELEASED;\r
  return SpinLock;\r
}\r
\r
/**\r
  Waits until a spin lock can be placed in the acquired state.\r
\r
  This function checks the state of the spin lock specified by SpinLock. If\r
  SpinLock is in the released state, then this function places SpinLock in the\r
  acquired state and returns SpinLock. Otherwise, this function waits\r
  indefinitely for the spin lock to be released, and then places it in the\r
  acquired state and returns SpinLock. All state transitions of SpinLock must\r
  be performed using MP safe mechanisms.\r
\r
  If SpinLock is NULL, then ASSERT().\r
  If SpinLock was not initialized with InitializeSpinLock(), then ASSERT().\r
  If PcdSpinLockTimeout is not zero, and SpinLock is can not be acquired in\r
  PcdSpinLockTimeout microseconds, then ASSERT().\r
\r
  @param  SpinLock  A pointer to the spin lock to place in the acquired state.\r
\r
  @return SpinLock\r
\r
**/\r
SPIN_LOCK *\r
EFIAPI\r
AcquireSpinLock (\r
  IN OUT  SPIN_LOCK                 *SpinLock\r
  )\r
{\r
  UINT64                            Tick;\r
  UINT64                            Start, End;\r
  UINT64                            Timeout;\r
\r
  Tick = 0;\r
  Start = 0;\r
  End = 0;\r
  if (PcdGet32 (PcdSpinLockTimeout) > 0) {\r
    Tick = GetPerformanceCounter ();\r
    Timeout = DivU64x32 (\r
                MultU64x32 (\r
                  GetPerformanceCounterProperties (&Start, &End),\r
                  PcdGet32 (PcdSpinLockTimeout)\r
                  ),\r
                1000000\r
                );\r
    if (Start < End) {\r
      Tick += Timeout;\r
    } else {\r
      Tick -= Timeout;\r
    }\r
  }\r
\r
  while (!AcquireSpinLockOrFail (SpinLock)) {\r
    CpuPause ();\r
    ASSERT ((Start < End) ^ (Tick <= GetPerformanceCounter ()));\r
  }\r
  return SpinLock;\r
}\r
\r
/**\r
  Attempts to place a spin lock in the acquired state.\r
\r
  This function checks the state of the spin lock specified by SpinLock. If\r
  SpinLock is in the released state, then this function places SpinLock in the\r
  acquired state and returns TRUE. Otherwise, FALSE is returned. All state\r
  transitions of SpinLock must be performed using MP safe mechanisms.\r
\r
  If SpinLock is NULL, then ASSERT().\r
  If SpinLock was not initialized with InitializeSpinLock(), then ASSERT().\r
\r
  @param  SpinLock  A pointer to the spin lock to place in the acquired state.\r
\r
  @retval TRUE  SpinLock was placed in the acquired state.\r
  @retval FALSE SpinLock could not be acquired.\r
\r
**/\r
BOOLEAN\r
EFIAPI\r
AcquireSpinLockOrFail (\r
  IN OUT  SPIN_LOCK                 *SpinLock\r
  )\r
{\r
  SPIN_LOCK    LockValue;\r
\r
  ASSERT (SpinLock != NULL);\r
\r
  LockValue = *SpinLock;\r
  ASSERT (LockValue == SPIN_LOCK_ACQUIRED || LockValue == SPIN_LOCK_RELEASED);\r
\r
  return (BOOLEAN)(\r
           InterlockedCompareExchangePointer (\r
             (VOID**)SpinLock,\r
             (VOID*)SPIN_LOCK_RELEASED,\r
             (VOID*)SPIN_LOCK_ACQUIRED\r
             ) == (VOID*)SPIN_LOCK_RELEASED\r
           );\r
}\r
\r
/**\r
  Releases a spin lock.\r
\r
  This function places the spin lock specified by SpinLock in the release state\r
  and returns SpinLock.\r
\r
  If SpinLock is NULL, then ASSERT().\r
  If SpinLock was not initialized with InitializeSpinLock(), then ASSERT().\r
\r
  @param  SpinLock  A pointer to the spin lock to release.\r
\r
  @return SpinLock\r
\r
**/\r
SPIN_LOCK *\r
EFIAPI\r
ReleaseSpinLock (\r
  IN OUT  SPIN_LOCK                 *SpinLock\r
  )\r
{\r
  SPIN_LOCK    LockValue;\r
\r
  ASSERT (SpinLock != NULL);\r
\r
  LockValue = *SpinLock;\r
  ASSERT (LockValue == SPIN_LOCK_ACQUIRED || LockValue == SPIN_LOCK_RELEASED);\r
\r
  *SpinLock = SPIN_LOCK_RELEASED;\r
  return SpinLock;\r
}\r
\r
/**\r
  Performs an atomic increment of an 32-bit unsigned integer.\r
\r
  Performs an atomic increment of the 32-bit unsigned integer specified by\r
  Value and returns the incremented value. The increment operation must be\r
  performed using MP safe mechanisms. The state of the return value is not\r
  guaranteed to be MP safe.\r
\r
  If Value is NULL, then ASSERT().\r
\r
  @param  Value A pointer to the 32-bit value to increment.\r
\r
  @return The incremented value.\r
\r
**/\r
UINT32\r
EFIAPI\r
InterlockedIncrement (\r
  IN      UINT32                    *Value\r
  )\r
{\r
  ASSERT (Value != NULL);\r
  return InternalSyncIncrement (Value);\r
}\r
\r
/**\r
  Performs an atomic decrement of an 32-bit unsigned integer.\r
\r
  Performs an atomic decrement of the 32-bit unsigned integer specified by\r
  Value and returns the decremented value. The decrement operation must be\r
  performed using MP safe mechanisms. The state of the return value is not\r
  guaranteed to be MP safe.\r
\r
  If Value is NULL, then ASSERT().\r
\r
  @param  Value A pointer to the 32-bit value to decrement.\r
\r
  @return The decremented value.\r
\r
**/\r
UINT32\r
EFIAPI\r
InterlockedDecrement (\r
  IN      UINT32                    *Value\r
  )\r
{\r
  ASSERT (Value != NULL);\r
  return InternalSyncDecrement (Value);\r
}\r
\r
/**\r
  Performs an atomic compare exchange operation on a 32-bit unsigned integer.\r
\r
  Performs an atomic compare exchange operation on the 32-bit unsigned integer\r
  specified by Value.  If Value is equal to CompareValue, then Value is set to \r
  ExchangeValue and CompareValue is returned.  If Value is not equal to CompareValue,\r
  then Value is returned.  The compare exchange operation must be performed using \r
  MP safe mechanisms.\r
\r
  If Value is NULL, then ASSERT().\r
\r
  @param  Value         A pointer to the 32-bit value for the compare exchange\r
                        operation.\r
  @param  CompareValue  32-bit value used in compare operation.\r
  @param  ExchangeValue 32-bit value used in exchange operation.\r
\r
  @return The original *Value before exchange.\r
\r
**/\r
UINT32\r
EFIAPI\r
InterlockedCompareExchange32 (\r
  IN OUT  UINT32                    *Value,\r
  IN      UINT32                    CompareValue,\r
  IN      UINT32                    ExchangeValue\r
  )\r
{\r
  ASSERT (Value != NULL);\r
  return InternalSyncCompareExchange32 (Value, CompareValue, ExchangeValue);\r
}\r
\r
/**\r
  Performs an atomic compare exchange operation on a 64-bit unsigned integer.\r
\r
  Performs an atomic compare exchange operation on the 64-bit unsigned integer specified \r
  by Value.  If Value is equal to CompareValue, then Value is set to ExchangeValue and \r
  CompareValue is returned.  If Value is not equal to CompareValue, then Value is returned. \r
  The compare exchange operation must be performed using MP safe mechanisms.\r
\r
  If Value is NULL, then ASSERT().\r
\r
  @param  Value         A pointer to the 64-bit value for the compare exchange\r
                        operation.\r
  @param  CompareValue  64-bit value used in compare operation.\r
  @param  ExchangeValue 64-bit value used in exchange operation.\r
\r
  @return The original *Value before exchange.\r
\r
**/\r
UINT64\r
EFIAPI\r
InterlockedCompareExchange64 (\r
  IN OUT  UINT64                    *Value,\r
  IN      UINT64                    CompareValue,\r
  IN      UINT64                    ExchangeValue\r
  )\r
{\r
  ASSERT (Value != NULL);\r
  return InternalSyncCompareExchange64 (Value, CompareValue, ExchangeValue);\r
}\r
\r
/**\r
  Performs an atomic compare exchange operation on a pointer value.\r
\r
  Performs an atomic compare exchange operation on the pointer value specified\r
  by Value. If Value is equal to CompareValue, then Value is set to\r
  ExchangeValue and CompareValue is returned. If Value is not equal to\r
  CompareValue, then Value is returned. The compare exchange operation must be\r
  performed using MP safe mechanisms.\r
\r
  If Value is NULL, then ASSERT().\r
\r
  @param  Value         A pointer to the pointer value for the compare exchange\r
                        operation.\r
  @param  CompareValue  Pointer value used in compare operation.\r
  @param  ExchangeValue Pointer value used in exchange operation.\r
\r
**/\r
VOID *\r
EFIAPI\r
InterlockedCompareExchangePointer (\r
  IN OUT  VOID                      **Value,\r
  IN      VOID                      *CompareValue,\r
  IN      VOID                      *ExchangeValue\r
  )\r
{\r
  UINT8  SizeOfValue;\r
\r
  SizeOfValue = sizeof (*Value);\r
\r
  switch (SizeOfValue) {\r
    case sizeof (UINT32):\r
      return (VOID*)(UINTN)InterlockedCompareExchange32 (\r
                             (UINT32*)Value,\r
                             (UINT32)(UINTN)CompareValue,\r
                             (UINT32)(UINTN)ExchangeValue\r
                             );\r
    case sizeof (UINT64):\r
      return (VOID*)(UINTN)InterlockedCompareExchange64 (\r
                             (UINT64*)Value,\r
                             (UINT64)(UINTN)CompareValue,\r
                             (UINT64)(UINTN)ExchangeValue\r
                             );\r
    default:\r
      ASSERT (FALSE);\r
      return NULL;\r
  }\r
}\r
Commit	Line	Data
e1f414b6	1	/** @file\r
	2	Implementation of synchronization functions.\r
	3	\r
	4	Copyright (c) 2006, Intel Corporation<BR>\r
	5	All rights reserved. This program and the accompanying materials\r
	6	are licensed and made available under the terms and conditions of the BSD License\r
	7	which accompanies this distribution. The full text of the license may be found at\r
	8	http://opensource.org/licenses/bsd-license.php\r
	9	\r
	10	THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
	11	WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
	12	\r
e1f414b6	13	**/\r
	14	\r
	15	//\r
	16	// Include common header file for this module.\r
	17	//\r
f734a10a	18	\r
e1f414b6	19	\r
	20	#include "BaseLibInternals.h"\r
	21	\r
	22	#define SPIN_LOCK_RELEASED ((UINTN) 1)\r
	23	#define SPIN_LOCK_ACQUIRED ((UINTN) 2)\r
	24	\r
	25	/**\r
	26	Retrieves the architecture specific spin lock alignment requirements for\r
	27	optimal spin lock performance.\r
	28	\r
	29	This function retrieves the spin lock alignment requirements for optimal\r
	30	performance on a given CPU architecture. The spin lock alignment must be a\r
	31	power of two and is returned by this function. If there are no alignment\r
	32	requirements, then 1 must be returned. The spin lock synchronization\r
	33	functions must function correctly if the spin lock size and alignment values\r
	34	returned by this function are not used at all. These values are hints to the\r
	35	consumers of the spin lock synchronization functions to obtain optimal spin\r
	36	lock performance.\r
	37	\r
	38	@return The architecture specific spin lock alignment.\r
	39	\r
	40	**/\r
	41	UINTN\r
	42	EFIAPI\r
	43	GetSpinLockProperties (\r
	44	VOID\r
	45	)\r
	46	{\r
	47	// @bug May use a PCD entry to determine this alignment.\r
	48	return 32;\r
	49	}\r
	50	\r
	51	/**\r
	52	Initializes a spin lock to the released state and returns the spin lock.\r
	53	\r
	54	This function initializes the spin lock specified by SpinLock to the released\r
	55	state, and returns SpinLock. Optimal performance can be achieved by calling\r
	56	GetSpinLockProperties() to determine the size and alignment requirements for\r
	57	SpinLock.\r
	58	\r
	59	If SpinLock is NULL, then ASSERT().\r
	60	\r
	61	@param SpinLock A pointer to the spin lock to initialize to the released\r
	62	state.\r
	63	\r
	64	@return SpinLock\r
	65	\r
	66	**/\r
	67	SPIN_LOCK *\r
	68	EFIAPI\r
	69	InitializeSpinLock (\r
	70	OUT SPIN_LOCK *SpinLock\r
	71	)\r
	72	{\r
	73	ASSERT (SpinLock != NULL);\r
	74	*SpinLock = SPIN_LOCK_RELEASED;\r
	75	return SpinLock;\r
	76	}\r
	77	\r
	78	/**\r
	79	Waits until a spin lock can be placed in the acquired state.\r
	80	\r
	81	This function checks the state of the spin lock specified by SpinLock. If\r
	82	SpinLock is in the released state, then this function places SpinLock in the\r
83	acquired state and returns SpinLock. Otherwise, this function waits\r
84	indefinitely for the spin lock to be released, and then places it in the\r
85	acquired state and returns SpinLock. All state transitions of SpinLock must\r
86	be performed using MP safe mechanisms.\r
87	\r
88	If SpinLock is NULL, then ASSERT().\r
89	If SpinLock was not initialized with InitializeSpinLock(), then ASSERT().\r
90	If PcdSpinLockTimeout is not zero, and SpinLock is can not be acquired in\r
91	PcdSpinLockTimeout microseconds, then ASSERT().\r
92	\r
93	@param SpinLock A pointer to the spin lock to place in the acquired state.\r
94	\r
95	@return SpinLock\r
96	\r
97	**/\r
98	SPIN_LOCK *\r
99	EFIAPI\r
100	AcquireSpinLock (\r
101	IN OUT SPIN_LOCK *SpinLock\r
102	)\r
103	{\r
104	UINT64 Tick;\r
105	UINT64 Start, End;\r
106	UINT64 Timeout;\r
107	\r
108	Tick = 0;\r
109	Start = 0;\r
110	End = 0;\r
111	if (PcdGet32 (PcdSpinLockTimeout) > 0) {\r
112	Tick = GetPerformanceCounter ();\r
113	Timeout = DivU64x32 (\r
114	MultU64x32 (\r
115	GetPerformanceCounterProperties (&Start, &End),\r
116	PcdGet32 (PcdSpinLockTimeout)\r
117	),\r
118	1000000\r
119	);\r
120	if (Start < End) {\r
121	Tick += Timeout;\r
122	} else {\r
123	Tick -= Timeout;\r
124	}\r
125	}\r
126	\r
127	while (!AcquireSpinLockOrFail (SpinLock)) {\r
128	CpuPause ();\r
129	ASSERT ((Start < End) ^ (Tick <= GetPerformanceCounter ()));\r
130	}\r
131	return SpinLock;\r
132	}\r
133	\r
134	/**\r
135	Attempts to place a spin lock in the acquired state.\r
136	\r
137	This function checks the state of the spin lock specified by SpinLock. If\r
138	SpinLock is in the released state, then this function places SpinLock in the\r
139	acquired state and returns TRUE. Otherwise, FALSE is returned. All state\r
140	transitions of SpinLock must be performed using MP safe mechanisms.\r
141	\r
142	If SpinLock is NULL, then ASSERT().\r
143	If SpinLock was not initialized with InitializeSpinLock(), then ASSERT().\r
144	\r
145	@param SpinLock A pointer to the spin lock to place in the acquired state.\r
146	\r
147	@retval TRUE SpinLock was placed in the acquired state.\r
148	@retval FALSE SpinLock could not be acquired.\r
149	\r
150	**/\r
151	BOOLEAN\r
152	EFIAPI\r
153	AcquireSpinLockOrFail (\r
154	IN OUT SPIN_LOCK *SpinLock\r
155	)\r
156	{\r
157	SPIN_LOCK LockValue;\r
158	\r
159	ASSERT (SpinLock != NULL);\r
160	\r
161	LockValue = *SpinLock;\r
162	ASSERT (LockValue == SPIN_LOCK_ACQUIRED \|\| LockValue == SPIN_LOCK_RELEASED);\r
163	\r
164	return (BOOLEAN)(\r
165	InterlockedCompareExchangePointer (\r
166	(VOID**)SpinLock,\r
167	(VOID*)SPIN_LOCK_RELEASED,\r
168	(VOID*)SPIN_LOCK_ACQUIRED\r
169	) == (VOID*)SPIN_LOCK_RELEASED\r
170	);\r
171	}\r
172	\r
173	/**\r
174	Releases a spin lock.\r
175	\r
176	This function places the spin lock specified by SpinLock in the release state\r
177	and returns SpinLock.\r
178	\r
179	If SpinLock is NULL, then ASSERT().\r
180	If SpinLock was not initialized with InitializeSpinLock(), then ASSERT().\r
181	\r
182	@param SpinLock A pointer to the spin lock to release.\r
183	\r
184	@return SpinLock\r
185	\r
186	**/\r
187	SPIN_LOCK *\r
188	EFIAPI\r
189	ReleaseSpinLock (\r
190	IN OUT SPIN_LOCK *SpinLock\r
191	)\r
192	{\r
193	SPIN_LOCK LockValue;\r
194	\r
195	ASSERT (SpinLock != NULL);\r
196	\r
197	LockValue = *SpinLock;\r
198	ASSERT (LockValue == SPIN_LOCK_ACQUIRED \|\| LockValue == SPIN_LOCK_RELEASED);\r
199	\r
200	*SpinLock = SPIN_LOCK_RELEASED;\r
201	return SpinLock;\r
202	}\r
203	\r
204	/**\r
205	Performs an atomic increment of an 32-bit unsigned integer.\r
206	\r
207	Performs an atomic increment of the 32-bit unsigned integer specified by\r
208	Value and returns the incremented value. The increment operation must be\r
209	performed using MP safe mechanisms. The state of the return value is not\r
210	guaranteed to be MP safe.\r
211	\r
212	If Value is NULL, then ASSERT().\r
213	\r
214	@param Value A pointer to the 32-bit value to increment.\r
215	\r
216	@return The incremented value.\r
217	\r
218	**/\r
219	UINT32\r
220	EFIAPI\r
221	InterlockedIncrement (\r
222	IN UINT32 *Value\r
223	)\r
224	{\r
225	ASSERT (Value != NULL);\r
226	return InternalSyncIncrement (Value);\r
227	}\r
228	\r
229	/**\r
230	Performs an atomic decrement of an 32-bit unsigned integer.\r
231	\r
232	Performs an atomic decrement of the 32-bit unsigned integer specified by\r
233	Value and returns the decremented value. The decrement operation must be\r
234	performed using MP safe mechanisms. The state of the return value is not\r
235	guaranteed to be MP safe.\r
236	\r
237	If Value is NULL, then ASSERT().\r
238	\r
239	@param Value A pointer to the 32-bit value to decrement.\r
240	\r
241	@return The decremented value.\r
242	\r
243	**/\r
244	UINT32\r
245	EFIAPI\r
246	InterlockedDecrement (\r
247	IN UINT32 *Value\r
248	)\r
249	{\r
250	ASSERT (Value != NULL);\r
251	return InternalSyncDecrement (Value);\r
252	}\r
253	\r
254	/**\r
255	Performs an atomic compare exchange operation on a 32-bit unsigned integer.\r
256	\r
257	Performs an atomic compare exchange operation on the 32-bit unsigned integer\r
258	specified by Value. If Value is equal to CompareValue, then Value is set to \r
259	ExchangeValue and CompareValue is returned. If Value is not equal to CompareValue,\r
260	then Value is returned. The compare exchange operation must be performed using \r
261	MP safe mechanisms.\r
262	\r
263	If Value is NULL, then ASSERT().\r
264	\r
265	@param Value A pointer to the 32-bit value for the compare exchange\r
266	operation.\r
267	@param CompareValue 32-bit value used in compare operation.\r
268	@param ExchangeValue 32-bit value used in exchange operation.\r
269	\r
270	@return The original *Value before exchange.\r
271	\r
272	**/\r
273	UINT32\r
274	EFIAPI\r
275	InterlockedCompareExchange32 (\r
276	IN OUT UINT32 *Value,\r
277	IN UINT32 CompareValue,\r
278	IN UINT32 ExchangeValue\r
279	)\r
280	{\r
281	ASSERT (Value != NULL);\r
282	return InternalSyncCompareExchange32 (Value, CompareValue, ExchangeValue);\r
283	}\r
284	\r
285	/**\r
286	Performs an atomic compare exchange operation on a 64-bit unsigned integer.\r
287	\r
288	Performs an atomic compare exchange operation on the 64-bit unsigned integer specified \r
289	by Value. If Value is equal to CompareValue, then Value is set to ExchangeValue and \r
290	CompareValue is returned. If Value is not equal to CompareValue, then Value is returned. \r
291	The compare exchange operation must be performed using MP safe mechanisms.\r
292	\r
293	If Value is NULL, then ASSERT().\r
294	\r
295	@param Value A pointer to the 64-bit value for the compare exchange\r
296	operation.\r
297	@param CompareValue 64-bit value used in compare operation.\r
298	@param ExchangeValue 64-bit value used in exchange operation.\r
299	\r
300	@return The original *Value before exchange.\r
301	\r
302	**/\r
303	UINT64\r
304	EFIAPI\r
305	InterlockedCompareExchange64 (\r
306	IN OUT UINT64 *Value,\r
307	IN UINT64 CompareValue,\r
308	IN UINT64 ExchangeValue\r
309	)\r
310	{\r
311	ASSERT (Value != NULL);\r
312	return InternalSyncCompareExchange64 (Value, CompareValue, ExchangeValue);\r
313	}\r
314	\r
315	/**\r
316	Performs an atomic compare exchange operation on a pointer value.\r
317	\r
318	Performs an atomic compare exchange operation on the pointer value specified\r
319	by Value. If Value is equal to CompareValue, then Value is set to\r
320	ExchangeValue and CompareValue is returned. If Value is not equal to\r
321	CompareValue, then Value is returned. The compare exchange operation must be\r
322	performed using MP safe mechanisms.\r
323	\r
324	If Value is NULL, then ASSERT().\r
325	\r
326	@param Value A pointer to the pointer value for the compare exchange\r
327	operation.\r
328	@param CompareValue Pointer value used in compare operation.\r
329	@param ExchangeValue Pointer value used in exchange operation.\r
330	\r
331	**/\r
332	VOID *\r
333	EFIAPI\r
334	InterlockedCompareExchangePointer (\r
335	IN OUT VOID **Value,\r
336	IN VOID *CompareValue,\r
337	IN VOID *ExchangeValue\r
338	)\r
339	{\r
340	UINT8 SizeOfValue;\r
341	\r
342	SizeOfValue = sizeof (*Value);\r
343	\r
344	switch (SizeOfValue) {\r
345	case sizeof (UINT32):\r
346	return (VOID*)(UINTN)InterlockedCompareExchange32 (\r
347	(UINT32*)Value,\r
348	(UINT32)(UINTN)CompareValue,\r
349	(UINT32)(UINTN)ExchangeValue\r
350	);\r
351	case sizeof (UINT64):\r
352	return (VOID*)(UINTN)InterlockedCompareExchange64 (\r
353	(UINT64*)Value,\r
354	(UINT64)(UINTN)CompareValue,\r
355	(UINT64)(UINTN)ExchangeValue\r
356	);\r
357	default:\r
358	ASSERT (FALSE);\r
359	return NULL;\r
360	}\r
361	}\r