Messages in this thread | | | Date | Sat, 20 Apr 2013 15:34:13 -0700 | From | Greg KH <> | Subject | Re: [PATCH] kref: minor cleanup |
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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.pomozov@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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