xnu-792.2.4.tar.gz

[apple/xnu.git] / libkern / gen / OSAtomicOperations.c

diff --git a/libkern/gen/OSAtomicOperations.c b/libkern/gen/OSAtomicOperations.c
index 735fa2ac3719d70c5a453d1b8e03bf299884134e..4a1e7beb065eaca5426fa1d30033a27dd3c97b07 100644 (file)
--- 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)