diff options
| author | Jason A. Donenfeld <Jason@zx2c4.com> | 2016-12-15 19:55:54 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-11 09:29:33 +0100 |
| commit | a0244a8df15d8caee8831872b6fc97b676cb15bd (patch) | |
| tree | 88ec73684fcf630db015b4da9d2a8cd6e8ce31b8 | |
| parent | e41746b0dd51f353630112558835aa62c1eb883e (diff) | |
kref: prefer atomic_inc_not_zero to atomic_add_unless
On most platforms, there exists this ifdef:
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
This makes this patch functionally useless. However, on PPC, there is
actually an explicit definition of atomic_inc_not_zero with its own
assembly that is slightly more optimized than atomic_add_unless. So,
this patch changes kref to use atomic_inc_not_zero instead, for PPC and
any future platforms that might provide an explicit implementation.
This also puts this usage of kref more in line with a verbatim reading
of the examples in Paul McKenney's paper [1] in the section titled "2.4
Atomic Counting With Check and Release Memory Barrier", which uses
atomic_inc_not_zero.
[1] http://open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2167.pdf
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | include/linux/kref.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/kref.h b/include/linux/kref.h index e15828fd71f1..62f0a84ae94e 100644 --- a/include/linux/kref.h +++ b/include/linux/kref.h @@ -133,6 +133,6 @@ static inline int kref_put_mutex(struct kref *kref, */ static inline int __must_check kref_get_unless_zero(struct kref *kref) { - return atomic_add_unless(&kref->refcount, 1, 0); + return atomic_inc_not_zero(&kref->refcount); } #endif /* _KREF_H_ */ |