On Sat, Apr 20, 2013 at 09:15:10AM -0700, Anatol Pomozov wrote:
> Follow-up for https://lkml.org/lkml/2013/4/12/391
That's not needed in a changelog comment.
> * make warning smp-safe
> * result of atomic _unless_zero functions should be checked by caller
> to avoid use-after-free error
You also do other things you don't list here.
>
> Signed-off-by: Anatol Pomozov <anatol.pomo...@gmail.com>
> ---
> include/linux/kobject.h | 1 +
> include/linux/kref.h | 9 ++++++---
> lib/kobject.c | 2 +-
> 3 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/kobject.h b/include/linux/kobject.h
> index 939b112..bfad936 100644
> --- a/include/linux/kobject.h
> +++ b/include/linux/kobject.h
> @@ -101,6 +101,7 @@ extern int __must_check kobject_rename(struct kobject *,
> const char *new_name);
> extern int __must_check kobject_move(struct kobject *, struct kobject *);
>
> extern struct kobject *kobject_get(struct kobject *kobj);
> +extern struct kobject * __must_check kobject_get_unless_zero(struct kobject
> *kobj);
Don't add apis that no one uses.
And even if you did, you forgot to export it to modules :(
> extern void kobject_put(struct kobject *kobj);
>
> extern char *kobject_get_path(struct kobject *kobj, gfp_t flag);
> diff --git a/include/linux/kref.h b/include/linux/kref.h
> index 4972e6e..817d7f1 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()
> + */
Did you use scripts/checkpatch.pl?
> + WARN_ON(atomic_inc_return(&kref->refcount) < 2);
As this is just a warning, I really doubt this type of change is needed,
have you ever hit it?
This is to catch people who forget to initialize a kref before doing the
first kref_get(), it's a help in debugging their code, nothing
"critical".
thanks,
greg k-h
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