X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=include%2Fasm-x86%2Fcmpxchg_64.h;h=17463ccf816618b59a144ec76f57e51589e8866c;hb=14cc571bb1d072d3f4be2875ea520ab03e093471;hp=d9b26b9a28cf9f0e3f64f4206f1922b331408f54;hpb=5f3b28781cbc030351e2fa0712602afbea592aae;p=linux-2.6-omap-h63xx.git

diff --git a/include/asm-x86/cmpxchg_64.h b/include/asm-x86/cmpxchg_64.h
index d9b26b9a28c..17463ccf816 100644
--- a/include/asm-x86/cmpxchg_64.h
+++ b/include/asm-x86/cmpxchg_64.h
@@ -93,6 +93,39 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
 	return old;
 }
 
+/*
+ * Always use locked operations when touching memory shared with a
+ * hypervisor, since the system may be SMP even if the guest kernel
+ * isn't.
+ */
+static inline unsigned long __sync_cmpxchg(volatile void *ptr,
+					   unsigned long old,
+					   unsigned long new, int size)
+{
+	unsigned long prev;
+	switch (size) {
+	case 1:
+		asm volatile("lock; cmpxchgb %b1,%2"
+			     : "=a"(prev)
+			     : "q"(new), "m"(*__xg(ptr)), "0"(old)
+			     : "memory");
+		return prev;
+	case 2:
+		asm volatile("lock; cmpxchgw %w1,%2"
+			     : "=a"(prev)
+			     : "r"(new), "m"(*__xg(ptr)), "0"(old)
+			     : "memory");
+		return prev;
+	case 4:
+		asm volatile("lock; cmpxchgl %1,%2"
+			     : "=a"(prev)
+			     : "r"(new), "m"(*__xg(ptr)), "0"(old)
+			     : "memory");
+		return prev;
+	}
+	return old;
+}
+
 static inline unsigned long __cmpxchg_local(volatile void *ptr,
 					    unsigned long old,
 					    unsigned long new, int size)
@@ -139,6 +172,10 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr,
 	((__typeof__(*(ptr)))__cmpxchg_local((ptr), (unsigned long)(o),	\
 					     (unsigned long)(n),	\
 					     sizeof(*(ptr))))
+#define sync_cmpxchg(ptr, o, n)						\
+	((__typeof__(*(ptr)))__sync_cmpxchg((ptr), (unsigned long)(o),	\
+					    (unsigned long)(n),		\
+					    sizeof(*(ptr))))
 #define cmpxchg64_local(ptr, o, n)					\
 ({									\
 	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\