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kref: minor cleanup

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- 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>
This commit is contained in:
Anatol Pomozov 2013-05-07 15:37:48 -07:00 committed by Linus Torvalds
parent 292088ee03
commit 2d864e4171
2 changed files with 7 additions and 4 deletions
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9
include/linux/kref.h
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@ -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);

2
lib/kobject.c
View File

@ -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;