linux-kernel - Re: [PATCH v2 2/2] drivers: core: Remove glue dirs from sysfs earlier

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Date:   Wed, 11 Jul 2018 09:31:05 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] drivers: core: Remove glue dirs from sysfs
 earlier

On Tue, 2018-07-10 at 16:55 +0200, Greg Kroah-Hartman wrote:
> 
> > +/**
> > + * kobject_has_children - Returns whether a kobject has children.
> > + * @kobj: the object to test
> > + *
> > + * This will return whether a kobject has other kobjects as children.
> > + *
> > + * It does NOT account for the presence of attribute files, only sub
> > + * directories. It also assumes there is no concurrent addition or
> > + * removal of such children, and thus relies on external locking.
> > + */
> > +static inline bool kobject_has_children(struct kobject *kobj)
> > +{
> > +	WARN_ON_ONCE(kref_read(&kobj->kref) == 0);
> 
> Why warn on?  Who is going to hit this and how are you going to fix up
> the syzbot reports?  :)

Well, that's it, the hope is nobody ever hits it ... but if one does it
would be useful to get a backtrace to figure it out. You can shoot the
reports my way I suppose :-)

> Anyway, this looks good, I can just take this and not the 1/2 patch now,
> right?  I really didn't like that patch.

Yes, it will fix the practical problem. As for patch 1, it's rather
funny, you and Linus seem to have a completely opposite idea of how
this stuff should work :-)

Cheers,
Ben.

> thanks,
> 
> greg k-h