Reduce code duplication in rundown protection

xtoskrnl/ex/rundown.cc

@@ -24,38 +24,8 @@ XTFASTCALL
 BOOLEAN
 EX::Rundown::AcquireProtection(IN PEX_RUNDOWN_REFERENCE Descriptor)
 {
-    ULONG_PTR CurrentValue, NewValue;
-
-    /* Get current value */
-    CurrentValue = Descriptor->Count;
-
-    /* Main loop execution */
-    while(TRUE)
-    {
-        /* Make sure protection is not active yet */
-        if(CurrentValue & 0x1)
-        {
-            /* Already active, nothing to do */
-            return FALSE;
-        }
-
-        /* Attempt to increment the usage count */
-        NewValue = CurrentValue + 2;
-
-        /* Exchange the value */
-        NewValue = (ULONG_PTR)RTL::Atomic::CompareExchangePointer(&Descriptor->Ptr, (PVOID)NewValue,
-                                                                  (PVOID)CurrentValue);
-
-        /* Make sure protection acquired */
-        if(NewValue == CurrentValue)
-        {
-            /* Successfully acquired protection */
-            return TRUE;
-        }
-
-        /* Update value and try once again */
-        CurrentValue = NewValue;
-    }
+    /* Acquire protection */
+    return AcquireProtection(Descriptor, 1);
 }
 
 /**
@@ -178,51 +148,8 @@ XTFASTCALL
 VOID
 EX::Rundown::ReleaseProtection(IN PEX_RUNDOWN_REFERENCE Descriptor)
 {
-    ULONG_PTR CurrentValue, NewValue;
-    PEX_RUNDOWN_WAIT_BLOCK WaitBlock;
-
-    /* Read the current state of the rundown descriptor */
-    CurrentValue = Descriptor->Count;
-
-    /* Enter a CAS loop */
-    while(TRUE)
-    {
-        /* Check if the rundown is currently active */
-        if(CurrentValue & 0x1)
-        {
-            /* Extract the pointer to the wait block */
-            WaitBlock = (PEX_RUNDOWN_WAIT_BLOCK)(CurrentValue & ~0x1);
-
-            /* Decrement the pending reference count */
-            if(!RTL::Atomic::Decrement64((PLONG_PTR)&WaitBlock->Count))
-            {
-                /* Signal the event to wake up the teardown thread */
-                KE::Event::SetEvent(&WaitBlock->WakeEvent, 0, FALSE);
-            }
-
-            /* Break the loop */
-            break;
-        }
-        else
-        {
-            /* Attempt to decrement the usage count */
-            NewValue = CurrentValue - 2;
-
-            /* Exchange the value */
-            NewValue = (ULONG_PTR)RTL::Atomic::CompareExchangePointer(&Descriptor->Ptr, (PVOID)NewValue,
-                                                                      (PVOID)CurrentValue);
-
-            /* Check if the atomic swap succeeded without interference from other processors */
-            if(NewValue == CurrentValue)
-            {
-                /* Reference count is decremented, break the loop */
-                break;
-            }
-
-            /* Collision detected, update current state and retry */
-            CurrentValue = NewValue;
-        }
-    }
+    /* Release protection */
+    ReleaseProtection(Descriptor, 1);
 }
 
 /**