From e4a683c899cd5a49f8d684a054c95bd115a0c005 Mon Sep 17 00:00:00 2001 From: Jerome Marchand Date: Wed, 5 Jan 2011 16:57:37 +0100 Subject: [PATCH] kref: add kref_test_and_get Add kref_test_and_get() function, which atomically add a reference only if refcount is not zero. This prevent to add a reference to an object that is already being removed. Signed-off-by: Jerome Marchand Cc: stable@kernel.org Signed-off-by: Jens Axboe --- include/linux/kref.h | 1 + lib/kref.c | 12 ++++++++++++ 2 files changed, 13 insertions(+) diff --git a/include/linux/kref.h b/include/linux/kref.h index 6cc38fc07ab..90b9e44abf5 100644 --- a/include/linux/kref.h +++ b/include/linux/kref.h @@ -23,6 +23,7 @@ struct kref { void kref_init(struct kref *kref); void kref_get(struct kref *kref); +int kref_test_and_get(struct kref *kref); int kref_put(struct kref *kref, void (*release) (struct kref *kref)); #endif /* _KREF_H_ */ diff --git a/lib/kref.c b/lib/kref.c index d3d227a08a4..e7a6e106712 100644 --- a/lib/kref.c +++ b/lib/kref.c @@ -36,6 +36,18 @@ void kref_get(struct kref *kref) smp_mb__after_atomic_inc(); } +/** + * kref_test_and_get - increment refcount for object only if refcount is not + * zero. + * @kref: object. + * + * Return non-zero if the refcount was incremented, 0 otherwise + */ +int kref_test_and_get(struct kref *kref) +{ + return atomic_inc_not_zero(&kref->refcount); +} + /** * kref_put - decrement refcount for object. * @kref: object. -- 2.39.2