This patch adds warning to detect kref_put() with unreferenced object.
The idea of detection kref_put() with unreferenced object was stolen
from BUG_ON()es in blocks/ll_rw_blk.c and fs/bio.c
ll_rw_blk.c: BUG_ON(atomic_read(&ioc->refcount) == 0);
bio.c: BIO_BUG_ON(!atomic_read(&bio->bi_cnt));
But the kref counter usually does not fall to zero. Because kref is
trying to reduce the number of atomic_dec_and_test()
So this patch also set kref counter to zero here:
+ if (atomic_read(&kref->refcount) == 1)
+ atomic_set(&kref->refcount, 0);
Signed-off-by: Akinobu Mita <[email protected]>
CC: Greg KH <[email protected]>
CC: Patrick Mochel <[email protected]>
lib/kref.c | 14 ++++++++------
1 files changed, 8 insertions(+), 6 deletions(-)
Index: 2.6-git/lib/kref.c
===================================================================
--- 2.6-git.orig/lib/kref.c
+++ 2.6-git/lib/kref.c
@@ -49,6 +49,7 @@ void kref_get(struct kref *kref)
*/
int kref_put(struct kref *kref, void (*release)(struct kref *kref))
{
+ WARN_ON(atomic_read(&kref->refcount) < 1);
WARN_ON(release == NULL);
WARN_ON(release == (void (*)(struct kref *))kfree);
@@ -56,12 +57,13 @@ int kref_put(struct kref *kref, void (*r
* if current count is one, we are the last user and can release object
* right now, avoiding an atomic operation on 'refcount'
*/
- if ((atomic_read(&kref->refcount) == 1) ||
- (atomic_dec_and_test(&kref->refcount))) {
- release(kref);
- return 1;
- }
- return 0;
+ if (atomic_read(&kref->refcount) == 1)
+ atomic_set(&kref->refcount, 0);
+ else if (!atomic_dec_and_test(&kref->refcount))
+ return 0;
+
+ release(kref);
+ return 1;
}
EXPORT_SYMBOL(kref_init);
--
-
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