[libvirt] [PATCH] Improve on virAtomic implementation
This patch improves on the previously added virAtomicInt operations
by testing for the compiler and if GCC >= 4.1 (not found in docs prior to
that) is used on Linux and has the appropriate processor (that I have
access to) then use the implementation based on the gcc-builtins.
I also did not look at other systems (cygwin, win32) that do not need
access to virAtomic right now.
---
src/util/viratomic.h | 88
+++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 72 insertions(+), 16 deletions(-)
Index: libvirt-acl/src/util/viratomic.h
===================================================================
--- libvirt-acl.orig/src/util/viratomic.h
+++ libvirt-acl/src/util/viratomic.h
@@ -30,6 +30,22 @@
typedef struct _virAtomicInt virAtomicInt;
typedef virAtomicInt *virAtomicIntPtr;
+# define __VIR_ATOMIC_USES_LOCK
+
+# if defined(__GNUC__)
+# if ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 1)) || (__GNUC__ > 4)
+# if defined(__linux__)
+# if defined(__i386__) || defined(__x86_64__) || \
+ defined(__powerpc64__) || defined(__powerpc__)
+# undef __VIR_ATOMIC_USES_LOCK
+# endif
+# endif
+# endif
+# endif
+
+
+# ifdef __VIR_ATOMIC_USES_LOCK
+
struct _virAtomicInt {
virMutex lock;
int value;
@@ -42,22 +58,6 @@ virAtomicIntInit(virAtomicIntPtr vaip)
return virMutexInit(&vaip->lock);
}
-static inline void
-virAtomicIntSet(virAtomicIntPtr vaip, int value)
-{
- virMutexLock(&vaip->lock);
-
- vaip->value = value;
-
- virMutexUnlock(&vaip->lock);
-}
-
-static inline int
-virAtomicIntRead(virAtomicIntPtr vaip)
-{
- return vaip->value;
-}
-
static inline int
virAtomicIntAdd(virAtomicIntPtr vaip, int add)
{
@@ -88,4 +88,60 @@ virAtomicIntSub(virAtomicIntPtr vaip, in
return ret;
}
+# else /* __VIR_ATOMIC_USES_LOCK */
+
+struct _virAtomicInt {
+ int value;
+};
+
+static inline int
+virAtomicIntInit(virAtomicIntPtr vaip)
+{
+ vaip->value = 0;
+ return 0;
+}
+
+static inline int
+virAtomicIntAdd(virAtomicIntPtr vaip, int add)
+{
+ return __sync_add_and_fetch(&vaip->value, add);
+}
+
+static inline int
+virAtomicIntSub(virAtomicIntPtr vaip, int sub)
+{
+ return __sync_sub_and_fetch(&vaip->value, sub);
+}
+
+# endif /* __VIR_ATOMIC_USES_LOCK */
+
+
+
+/* common operations that need no locking or build on others */
+
+
+static inline void
+virAtomicIntSet(virAtomicIntPtr vaip, int value)
+{
+ vaip->value = value;
+}
+
+static inline int
+virAtomicIntRead(virAtomicIntPtr vaip)
+{
+ return *(volatile int *)&vaip->value;
+}
+
+static inline int
+virAtomicIntInc(virAtomicIntPtr vaip)
+{
+ return virAtomicIntAdd(vaip, 1);
+}
+
+static inline int
+virAtomicIntDec(virAtomicIntPtr vaip)
+{
+ return virAtomicIntSub(vaip, 1);
+}
+
#endif /* __VIR_ATOMIC_H */