UAS: Use unique tags on non-streams devices.

[linux-flexiantxendom0.git] / lib / kref.c

diff --git a/lib/kref.c b/lib/kref.c
index 0d07cc3..3efb882 100644 (file)
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -13,6 +13,7 @@
 
 #include <linux/kref.h>
 #include <linux/module.h>
+#include <linux/slab.h>
 
 /**
  * kref_init - initialize object.
@@ -20,7 +21,8 @@
  */
 void kref_init(struct kref *kref)
 {
-       atomic_set(&kref->refcount,1);
+       atomic_set(&kref->refcount, 1);
+       smp_mb();
 }
 
 /**
@@ -31,6 +33,7 @@ void kref_get(struct kref *kref)
 {
        WARN_ON(!atomic_read(&kref->refcount));
        atomic_inc(&kref->refcount);
+       smp_mb__after_atomic_inc();
 }
 
 /**
@@ -59,6 +62,36 @@ int kref_put(struct kref *kref, void (*release)(struct kref *kref))
        return 0;
 }
 
+
+/**
+ * kref_sub - subtract a number of refcounts for object.
+ * @kref: object.
+ * @count: Number of recounts to subtract.
+ * @release: pointer to the function that will clean up the object when the
+ *          last reference to the object is released.
+ *          This pointer is required, and it is not acceptable to pass kfree
+ *          in as this function.
+ *
+ * Subtract @count from the refcount, and if 0, call release().
+ * Return 1 if the object was removed, otherwise return 0.  Beware, if this
+ * function returns 0, you still can not count on the kref from remaining in
+ * memory.  Only use the return value if you want to see if the kref is now
+ * gone, not present.
+ */
+int kref_sub(struct kref *kref, unsigned int count,
+            void (*release)(struct kref *kref))
+{
+       WARN_ON(release == NULL);
+       WARN_ON(release == (void (*)(struct kref *))kfree);
+
+       if (atomic_sub_and_test((int) count, &kref->refcount)) {
+               release(kref);
+               return 1;
+       }
+       return 0;
+}
+
 EXPORT_SYMBOL(kref_init);
 EXPORT_SYMBOL(kref_get);
 EXPORT_SYMBOL(kref_put);
+EXPORT_SYMBOL(kref_sub);