Update EBC sub-dir of BaseLib according to code review comments.

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

diff --git a/MdePkg/Library/BaseLib/SynchronizationMsc.c b/MdePkg/Library/BaseLib/SynchronizationMsc.c
index fb10b5d01b59fceff5e0377e8a26c3653c3aa290..de271aea26a92ef7ca808756e7a2afcace53bbd6 100644 (file)
--- a/MdePkg/Library/BaseLib/SynchronizationMsc.c
+++ b/MdePkg/Library/BaseLib/SynchronizationMsc.c
@@ -10,15 +10,16 @@
   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
-  Module Name:  SynchronizationMsc.c\r
-\r
 **/\r
 \r
+\r
+\r
+\r
 #include "BaseLibInternals.h"\r
 \r
-//\r
-// Microsoft Visual Studio 7.1 Function Prototypes for read write barrier Intrinsics\r
-//\r
+/**\r
+  Microsoft Visual Studio 7.1 Function Prototypes for read write barrier Intrinsics.\r
+**/\r
 void    _ReadWriteBarrier (void);\r
 #pragma intrinsic(_ReadWriteBarrier)\r
 \r
@@ -48,7 +49,6 @@ GetSpinLockProperties (
   VOID\r
   )\r
 {\r
-  // @bug May use a PCD entry to determine this alignment.\r
   return 32;\r
 }\r
 \r
@@ -65,7 +65,7 @@ GetSpinLockProperties (
   @param  SpinLock  A pointer to the spin lock to initialize to the released\r
                     state.\r
 \r
-  @return SpinLock\r
+  @return SpinLock in released state.\r
 \r
 **/\r
 SPIN_LOCK *\r
@@ -100,7 +100,7 @@ InitializeSpinLock (
 \r
   @param  SpinLock  A pointer to the spin lock to place in the acquired state.\r
 \r
-  @return SpinLock\r
+  @return SpinLock aquiring lock.\r
 \r
 **/\r
 SPIN_LOCK *\r
@@ -109,15 +109,32 @@ AcquireSpinLock (
   IN OUT  SPIN_LOCK                 *SpinLock\r
   )\r
 {\r
-  UINT64                            Tick;\r
-  UINT64                            Start, End;\r
-  UINT64                            Timeout;\r
+  UINT64  Current;\r
+  UINT64  Previous;\r
+  UINT64  Total;\r
+  UINT64  Start;\r
+  UINT64  End;\r
+  UINT64  Timeout;\r
+  INT64   Cycle;\r
+  INT64   Delta;\r
 \r
-  Tick = 0;\r
-  Start = 0;\r
-  End = 0;\r
   if (PcdGet32 (PcdSpinLockTimeout) > 0) {\r
-    Tick = GetPerformanceCounter ();\r
+    //\r
+    // Get the current timer value\r
+    //\r
+    Current = GetPerformanceCounter();\r
+\r
+    //\r
+    // Initialize local variables\r
+    //\r
+    Start = 0;\r
+    End   = 0;\r
+    Total = 0;\r
+\r
+    //\r
+    // Retrieve the performance counter properties and compute the number of performance\r
+    // counter ticks required to reach the timeout\r
+    //\r
     Timeout = DivU64x32 (\r
                 MultU64x32 (\r
                   GetPerformanceCounterProperties (&Start, &End),\r
@@ -125,16 +142,30 @@ AcquireSpinLock (
                   ),\r
                 1000000\r
                 );\r
-    if (Start < End) {\r
-      Tick += Timeout;\r
-    } else {\r
-      Tick -= Timeout;\r
+    Cycle = End - Start;\r
+    if (Cycle < 0) {\r
+      Cycle = -Cycle;\r
+    }\r
+    Cycle++;\r
+\r
+    while (!AcquireSpinLockOrFail (SpinLock)) {\r
+      CpuPause ();\r
+      Previous = Current;\r
+      Current  = GetPerformanceCounter();\r
+      Delta = (INT64) (Current - Previous);\r
+      if (Start > End) {\r
+        Delta = -Delta;\r
+      }\r
+      if (Delta < 0) {\r
+        Delta += Cycle;\r
+      }\r
+      Total += Delta;\r
+      ASSERT (Total < Timeout);\r
+    }\r
+  } else {\r
+    while (!AcquireSpinLockOrFail (SpinLock)) {\r
+      CpuPause ();\r
     }\r
-  }\r
-\r
-  while (!AcquireSpinLockOrFail (SpinLock)) {\r
-    CpuPause ();\r
-    ASSERT ((Start < End) ^ (Tick <= GetPerformanceCounter ()));\r
   }\r
   return SpinLock;\r
 }\r
@@ -162,10 +193,13 @@ AcquireSpinLockOrFail (
   IN OUT  SPIN_LOCK                 *SpinLock\r
   )\r
 {\r
-  VOID  *Result;\r
+  SPIN_LOCK   LockValue;\r
+  VOID        *Result;\r
   \r
   ASSERT (SpinLock != NULL);\r
-  ASSERT (*SpinLock == SPIN_LOCK_ACQUIRED || *SpinLock == SPIN_LOCK_RELEASED);\r
+\r
+  LockValue = *SpinLock;\r
+  ASSERT (LockValue == SPIN_LOCK_ACQUIRED || LockValue == SPIN_LOCK_RELEASED);\r
 \r
   _ReadWriteBarrier ();\r
   Result = InterlockedCompareExchangePointer (\r
@@ -189,7 +223,7 @@ AcquireSpinLockOrFail (
 \r
   @param  SpinLock  A pointer to the spin lock to release.\r
 \r
-  @return SpinLock\r
+  @return SpinLock releasing lock.\r
 \r
 **/\r
 SPIN_LOCK *\r
@@ -198,8 +232,12 @@ ReleaseSpinLock (
   IN OUT  SPIN_LOCK                 *SpinLock\r
   )\r
 {\r
+  SPIN_LOCK    LockValue;\r
+\r
   ASSERT (SpinLock != NULL);\r
-  ASSERT (*SpinLock == SPIN_LOCK_ACQUIRED || *SpinLock == SPIN_LOCK_RELEASED);\r
+\r
+  LockValue = *SpinLock;\r
+  ASSERT (LockValue == SPIN_LOCK_ACQUIRED || LockValue == SPIN_LOCK_RELEASED);\r
 \r
   _ReadWriteBarrier ();\r
   *SpinLock = SPIN_LOCK_RELEASED;\r
@@ -334,6 +372,8 @@ InterlockedCompareExchange64 (
                         operation.\r
   @param  CompareValue  Pointer value used in compare operation.\r
   @param  ExchangeValue Pointer value used in exchange operation.\r
+  \r
+  @return The original *Value before exchange.\r
 \r
 **/\r
 VOID *\r