Makes it possible to optimize batched multiple unrefs.
Initial user will be drivers/gpu/ttm which accumulates unrefs to be
processed outside of atomic code.
Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
---
include/linux/kref.h | 2 ++
lib/kref.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 32 insertions(+), 0 deletions(-)
diff --git a/include/linux/kref.h b/include/linux/kref.h
index 6cc38fc..d4a62ab 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -24,5 +24,7 @@ struct kref {
void kref_init(struct kref *kref);
void kref_get(struct kref *kref);
int kref_put(struct kref *kref, void (*release) (struct kref *kref));
+int kref_sub(struct kref *kref, unsigned int count,
+ void (*release) (struct kref *kref));
#endif /* _KREF_H_ */
diff --git a/lib/kref.c b/lib/kref.c
index d3d227a..3efb882 100644
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -62,6 +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);
--
1.6.2.5
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