patch-2.3.31 linux/include/asm-i386/system.h

• Lines: 59
• Date: Tue Dec 7 14:10:48 1999
• Orig file: v2.3.30/linux/include/asm-i386/system.h
• Orig date: Tue Dec 7 09:32:49 1999

diff -u --recursive --new-file v2.3.30/linux/include/asm-i386/system.h linux/include/asm-i386/system.h
@@ -3,6 +3,7 @@
 
 #include <linux/kernel.h>
 #include <asm/segment.h>
+#include <linux/bitops.h> /* for LOCK_PREFIX */
 
 #ifdef __KERNEL__
 
@@ -207,6 +208,50 @@
 	}
 	return x;
 }
+
+/*
+ * Atomic compare and exchange.  Compare OLD with MEM, if identical,
+ * store NEW in MEM.  Return the initial value in MEM.  Success is
+ * indicated by comparing RETURN with OLD.
+ */
+
+#if CPU != 386
+#define __HAVE_ARCH_CMPXCHG 1
+
+static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
+				      unsigned long new, int size)
+{
+	unsigned long prev;
+	switch (size) {
+	case 1:
+		__asm__ __volatile__(LOCK_PREFIX "cmpxchgb %b1,%2"
+				     : "=a"(prev)
+				     : "q"(new), "m"(*__xg(ptr)), "0"(old)
+				     : "memory");
+		return prev;
+	case 2:
+		__asm__ __volatile__(LOCK_PREFIX "cmpxchgw %w1,%2"
+				     : "=a"(prev)
+				     : "q"(new), "m"(*__xg(ptr)), "0"(old)
+				     : "memory");
+		return prev;
+	case 4:
+		__asm__ __volatile__(LOCK_PREFIX "cmpxchgl %1,%2"
+				     : "=a"(prev)
+				     : "q"(new), "m"(*__xg(ptr)), "0"(old)
+				     : "memory");
+		return prev;
+	}
+	return old;
+}
+
+#define cmpxchg(ptr,o,n)\
+	((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\
+					(unsigned long)(n),sizeof(*(ptr))))
+    
+#else
+/* Compiling for a 386 proper.	Is it worth implementing via cli/sti?  */
+#endif
 
 /*
  * Force strict CPU ordering.