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From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Naresh Kamboju <naresh.kamboju@linaro.org>,
	kernel test robot <rong.a.chen@intel.com>,
	Brendan Higgins <brendanhiggins@google.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH] kobject: Make sure the parent does not get released before its children
Date: Wed, 13 May 2020 17:51:18 +0200	[thread overview]
Message-ID: <CAJZ5v0jzF6HM41UBaWfuJ38TMg+jq+1pQAz0QHb9GwTDJV_F=Q@mail.gmail.com> (raw)
In-Reply-To: <20200513154228.GC1360420@kroah.com>

On Wed, May 13, 2020 at 5:42 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Wed, May 13, 2020 at 06:18:40PM +0300, Heikki Krogerus wrote:
> > In the function kobject_cleanup(), kobject_del(kobj) is
> > called before the kobj->release(). That makes it possible to
> > release the parent of the kobject before the kobject itself.
> >
> > To fix that, adding function __kboject_del() that does
> > everything that kobject_del() does except release the parent
> > reference. kobject_cleanup() then calls __kobject_del()
> > instead of kobject_del(), and separately decrements the
> > reference count of the parent kobject after kobj->release()
> > has been called.
> >
> > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> > Reported-by: kernel test robot <rong.a.chen@intel.com>
> > Fixes: 7589238a8cf3 ("Revert "software node: Simplify software_node_release() function"")
> > Cc: Brendan Higgins <brendanhiggins@google.com>
> > Cc: Randy Dunlap <rdunlap@infradead.org>
> > Suggested-by: "Rafael J. Wysocki" <rafael@kernel.org>
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > ---
> >  lib/kobject.c | 30 ++++++++++++++++++++----------
> >  1 file changed, 20 insertions(+), 10 deletions(-)
> >
> > diff --git a/lib/kobject.c b/lib/kobject.c
> > index 65fa7bf70c57..32432036bef8 100644
> > --- a/lib/kobject.c
> > +++ b/lib/kobject.c
> > @@ -599,14 +599,7 @@ int kobject_move(struct kobject *kobj, struct kobject *new_parent)
> >  }
> >  EXPORT_SYMBOL_GPL(kobject_move);
> >
> > -/**
> > - * kobject_del() - Unlink kobject from hierarchy.
> > - * @kobj: object.
> > - *
> > - * This is the function that should be called to delete an object
> > - * successfully added via kobject_add().
> > - */
> > -void kobject_del(struct kobject *kobj)
> > +static void __kobject_del(struct kobject *kobj)
> >  {
> >       struct kernfs_node *sd;
> >       const struct kobj_type *ktype;
> > @@ -625,9 +618,23 @@ void kobject_del(struct kobject *kobj)
> >
> >       kobj->state_in_sysfs = 0;
> >       kobj_kset_leave(kobj);
> > -     kobject_put(kobj->parent);
> >       kobj->parent = NULL;
> >  }
> > +
> > +/**
> > + * kobject_del() - Unlink kobject from hierarchy.
> > + * @kobj: object.
> > + *
> > + * This is the function that should be called to delete an object
> > + * successfully added via kobject_add().
> > + */
> > +void kobject_del(struct kobject *kobj)
> > +{
> > +     struct kobject *parent = kobj->parent;
> > +
> > +     __kobject_del(kobj);
> > +     kobject_put(parent);
> > +}
> >  EXPORT_SYMBOL(kobject_del);
> >
> >  /**
> > @@ -663,6 +670,7 @@ EXPORT_SYMBOL(kobject_get_unless_zero);
> >   */
> >  static void kobject_cleanup(struct kobject *kobj)
> >  {
> > +     struct kobject *parent = kobj->parent;
> >       struct kobj_type *t = get_ktype(kobj);
> >       const char *name = kobj->name;
> >
> > @@ -684,7 +692,7 @@ static void kobject_cleanup(struct kobject *kobj)
> >       if (kobj->state_in_sysfs) {
> >               pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n",
> >                        kobject_name(kobj), kobj);
> > -             kobject_del(kobj);
> > +             __kobject_del(kobj);
> >       }
> >
> >       if (t && t->release) {
> > @@ -698,6 +706,8 @@ static void kobject_cleanup(struct kobject *kobj)
> >               pr_debug("kobject: '%s': free name\n", name);
> >               kfree_const(name);
> >       }
> > +
> > +     kobject_put(parent);
> >  }
> >
> >  #ifdef CONFIG_DEBUG_KOBJECT_RELEASE
> > --
> > 2.26.2
> >
>
> Is this the older patch we talked about before, or something else?
>
> I can't remember how we left that thread...

This is an alternative that you said might work. :-)

  reply	other threads:[~2020-05-13 15:51 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13 15:18 [PATCH] kobject: Make sure the parent does not get released before its children Heikki Krogerus
2020-05-13 15:20 ` Rafael J. Wysocki
2020-05-13 15:42 ` Greg Kroah-Hartman
2020-05-13 15:51   ` Rafael J. Wysocki [this message]
2020-05-13 20:18 ` Brendan Higgins
2020-05-13 20:54   ` Randy Dunlap
2020-05-13 21:30 ` Brendan Higgins
2020-05-13 23:14   ` Randy Dunlap
2020-05-14  6:54     ` Heikki Krogerus
2020-05-15 15:10       ` Greg Kroah-Hartman
2020-05-23 13:21 ` Guenter Roeck
2020-05-23 13:29   ` Guenter Roeck
2020-05-23 14:04   ` Greg Kroah-Hartman
2020-05-23 15:36 ` Greg Kroah-Hartman
2020-05-23 15:44   ` Randy Dunlap
2020-05-23 19:04     ` Dmitry Torokhov
2020-05-24 11:42       ` Greg Kroah-Hartman
2020-05-24 12:57     ` Greg Kroah-Hartman
2020-05-24 13:14       ` Greg Kroah-Hartman
2020-05-24 13:28         ` Greg Kroah-Hartman
2020-05-24 15:35           ` Greg Kroah-Hartman

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