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| author | Anatol Pomozov <anatol.pomozov@gmail.com> | 2013-05-07 15:37:48 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-05-07 16:09:00 -0700 |
| commit | 2d864e41710f1d2ba406fb62018ab0487152e6f2 (patch) | |
| tree | 52c6a3172b7a4099830962323f2a1742fa166b01 | |
| parent | 292088ee032d0df59e7c8a7a00e9b97260146078 (diff) | |
| download | lwn-2d864e41710f1d2ba406fb62018ab0487152e6f2.tar.gz lwn-2d864e41710f1d2ba406fb62018ab0487152e6f2.zip | |
kref: minor cleanup
- make warning smp-safe
- result of atomic _unless_zero functions should be checked by caller
to avoid use-after-free error
- trivial whitespace fix.
Link: https://lkml.org/lkml/2013/4/12/391
Tested: compile x86, boot machine and run xfstests
Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
[ Removed line-break, changed to use WARN_ON_ONCE() - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/kref.h | 9 | ||||
| -rw-r--r-- | lib/kobject.c | 2 |
2 files changed, 7 insertions, 4 deletions
diff --git a/include/linux/kref.h b/include/linux/kref.h index 4972e6e9ca93..e15828fd71f1 100644 --- a/include/linux/kref.h +++ b/include/linux/kref.h @@ -39,8 +39,11 @@ static inline void kref_init(struct kref *kref) */ static inline void kref_get(struct kref *kref) { - WARN_ON(!atomic_read(&kref->refcount)); - atomic_inc(&kref->refcount); + /* If refcount was 0 before incrementing then we have a race + * condition when this kref is freeing by some other thread right now. + * In this case one should use kref_get_unless_zero() + */ + WARN_ON_ONCE(atomic_inc_return(&kref->refcount) < 2); } /** @@ -100,7 +103,7 @@ static inline int kref_put_mutex(struct kref *kref, struct mutex *lock) { WARN_ON(release == NULL); - if (unlikely(!atomic_add_unless(&kref->refcount, -1, 1))) { + if (unlikely(!atomic_add_unless(&kref->refcount, -1, 1))) { mutex_lock(lock); if (unlikely(!atomic_dec_and_test(&kref->refcount))) { mutex_unlock(lock); diff --git a/lib/kobject.c b/lib/kobject.c index a65486613d79..b7e29a6056d3 100644 --- a/lib/kobject.c +++ b/lib/kobject.c @@ -529,7 +529,7 @@ struct kobject *kobject_get(struct kobject *kobj) return kobj; } -static struct kobject *kobject_get_unless_zero(struct kobject *kobj) +static struct kobject * __must_check kobject_get_unless_zero(struct kobject *kobj) { if (!kref_get_unless_zero(&kobj->kref)) kobj = NULL; |