X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/1c79356b52d46aa6b508fb032f5ae709b1f2897b..cc9f6e38162d3c1bf6ca97536c2477f476c8e01b:/libkern/gen/OSAtomicOperations.c?ds=inline

diff --git a/libkern/gen/OSAtomicOperations.c b/libkern/gen/OSAtomicOperations.c
index 735fa2ac3..4a1e7beb0 100644
--- a/libkern/gen/OSAtomicOperations.c
+++ b/libkern/gen/OSAtomicOperations.c
@@ -39,6 +39,11 @@ enum {
  *	which I wrote for NuKernel in a previous life with a different last name...)
  *
  * native Boolean	CompareAndSwap(UInt32 oldValue, UInt32 newValue, UInt32 * oldValuePtr);
+ *
+ * We've since implemented a few more of these -- OSAddAtomic, OSDequeueAtomic,
+ * OSEnqueueAtomic etc -- in assembler, either for speed or correctness.  See also the
+ * commpage atomic operations, and the platform specific versions.
+ * Like standards, there are a lot of atomic ops to choose from!
  */
 
 #ifndef __ppc__
@@ -66,6 +71,37 @@ SInt32	OSDecrementAtomic(SInt32 * value)
 	return OSAddAtomic(-1, value);
 }
 
+void *	OSDequeueAtomic(void ** inList, SInt32 inOffset)
+{
+	void *	oldListHead;
+	void *	newListHead;
+	
+	do {
+		oldListHead = *inList;
+		if (oldListHead == NULL) {
+			break;
+		}
+		
+		newListHead = *(void **) (((char *) oldListHead) + inOffset);
+	} while (! OSCompareAndSwap((UInt32)oldListHead,
+					(UInt32)newListHead, (UInt32 *)inList));
+	
+	return oldListHead;
+}
+
+void	OSEnqueueAtomic(void ** inList, void * inNewLink, SInt32 inOffset)
+{
+	void *	oldListHead;
+	void *	newListHead = inNewLink;
+	void **	newLinkNextPtr = (void **) (((char *) inNewLink) + inOffset);
+	
+	do {
+		oldListHead = *inList;
+		*newLinkNextPtr = oldListHead;
+	} while (! OSCompareAndSwap((UInt32)oldListHead, (UInt32)newListHead,
+					(UInt32 *)inList));
+}
+
 #endif	/* !__ppc__ */
 
 static UInt32	OSBitwiseAtomic(UInt32 and_mask, UInt32 or_mask, UInt32 xor_mask, UInt32 * value)
@@ -96,45 +132,23 @@ UInt32	OSBitXorAtomic(UInt32 mask, UInt32 * value)
 	return OSBitwiseAtomic((UInt32) -1, 0, mask, value);
 }
 
-
-static Boolean	OSCompareAndSwap8(UInt8 oldValue8, UInt8 newValue8, UInt8 * value8)
+static Boolean OSCompareAndSwap8(UInt8 oldValue8, UInt8 newValue8, UInt8 * value8)
 {
-	UInt32		mask = 0x000000ff;
-	UInt32		newbits = (UInt32) newValue8;
-	int			shift;
-	UInt32		alignment = ((UInt32) value8) & (sizeof(UInt32) - 1);
-	UInt32		oldValue;
-	UInt32		newValue;
-	UInt32 *	value;
-
-	switch (alignment) {
-		default:
-			// assert(false);
-		case 0:
-			value = (UInt32 *) value8;
-			shift = 24;
-			break;
-		case 1:
-			value = (UInt32 *) (value8 + 1);
-			shift = 16;
-			break;
-		case 2:
-			value = (UInt32 *) (value8 + 2);
-			shift = 8;
-			break;
-		case 3:
-			value = (UInt32 *) (value8 + 3);
-			shift = 0;
-			break;
-	}
+	UInt32		mask        = 0x000000ff;
+	UInt32		alignment   = ((UInt32) value8) & (sizeof(UInt32) - 1);
+    UInt32      shiftValues = (24 << 24) | (16 << 16) | (8 << 8);
+    int			shift       = (UInt32) *(((UInt8 *) &shiftValues) + alignment);
+	UInt32 *	value32     = (UInt32 *) (value8 - alignment);
+    UInt32      oldValue;
+    UInt32      newValue;
 
-	mask <<= shift;
-	newbits <<= shift;
-	
-	oldValue = *value;
-	newValue = (oldValue & ~mask) | (newbits & mask);
-	
-	return OSCompareAndSwap(oldValue, newValue, value);
+    mask <<= shift;
+
+    oldValue = *value32;
+    oldValue = (oldValue & ~mask) | (oldValue8 << shift);
+    newValue = (oldValue & ~mask) | (newValue8 << shift);
+
+	return OSCompareAndSwap(oldValue, newValue, value32);
 }
 
 static Boolean	OSTestAndSetClear(UInt32 bit, Boolean wantSet, UInt8 * startAddress)
@@ -167,37 +181,6 @@ Boolean	OSTestAndClear(UInt32 bit, UInt8 * startAddress)
 	return OSTestAndSetClear(bit, false, startAddress);
 }
 
-void *	OSDequeueAtomic(void ** inList, SInt32 inOffset)
-{
-	void *	oldListHead;
-	void *	newListHead;
-	
-	do {
-		oldListHead = *inList;
-		if (oldListHead == NULL) {
-			break;
-		}
-		
-		newListHead = *(void **) (((char *) oldListHead) + inOffset);
-	} while (! OSCompareAndSwap((UInt32)oldListHead,
-					(UInt32)newListHead, (UInt32 *)inList));
-	
-	return oldListHead;
-}
-
-void	OSEnqueueAtomic(void ** inList, void * inNewLink, SInt32 inOffset)
-{
-	void *	oldListHead;
-	void *	newListHead = inNewLink;
-	void **	newLinkNextPtr = (void **) (((char *) inNewLink) + inOffset);
-	
-	do {
-		oldListHead = *inList;
-		*newLinkNextPtr = oldListHead;
-	} while (! OSCompareAndSwap((UInt32)oldListHead, (UInt32)newListHead,
-					(UInt32 *)inList));
-}
-
 /*
  * silly unaligned versions
  */
@@ -253,34 +236,23 @@ UInt8	OSBitXorAtomic8(UInt32 mask, UInt8 * value)
 	return OSBitwiseAtomic8((UInt32) -1, 0, mask, value);
 }
 
-
-static Boolean	OSCompareAndSwap16(UInt16 oldValue16, UInt16 newValue16, UInt16 * value16)
+static Boolean OSCompareAndSwap16(UInt16 oldValue16, UInt16 newValue16, UInt16 * value16)
 {
-	UInt32		mask = 0x0000ffff;
-	UInt32		newbits = (UInt32) newValue16;
-	int			shift;
-	UInt32		alignment = ((UInt32) value16) & (sizeof(UInt32) - 1);
-	UInt32		oldValue;
-	UInt32		newValue;
-	UInt32 *	value;
-
-	if (alignment == 2) {
-		value = (UInt32 *) (value16 - 1);
-		shift = 0;
-	}
-	else {
-		// assert(alignment == 0);
-		value = (UInt32 *) value16;
-		shift = 16;
-	}
-
-	mask <<= shift;
-	newbits <<= shift;
-	
-	oldValue = *value;
-	newValue = (oldValue & ~mask) | (newbits & mask);
-	
-	return OSCompareAndSwap(oldValue, newValue, value);
+	UInt32		mask        = 0x0000ffff;
+	UInt32		alignment   = ((UInt32) value16) & (sizeof(UInt32) - 1);
+    UInt32      shiftValues = (16 << 24) | (16 << 16);
+    UInt32		shift       = (UInt32) *(((UInt8 *) &shiftValues) + alignment);
+	UInt32 *	value32     = (UInt32 *) (((UInt32) value16) - alignment);
+    UInt32      oldValue;
+    UInt32      newValue;
+
+    mask <<= shift;
+
+    oldValue = *value32;
+    oldValue = (oldValue & ~mask) | (oldValue16 << shift);
+    newValue = (oldValue & ~mask) | (newValue16 << shift);
+
+	return OSCompareAndSwap(oldValue, newValue, value32);
 }
 
 SInt16	OSIncrementAtomic16(SInt16 * value)