linux-kernel - Re: [PATCH 1/2] livepatch: Remove custom kobject state handling

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Date:   Tue, 7 May 2019 15:06:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     Petr Mladek <pmladek@...e.com>, Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
        "Tobin C . Harding" <tobin@...nel.org>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] livepatch: Remove custom kobject state handling

On Tue, May 07, 2019 at 02:32:57PM +0200, Miroslav Benes wrote:
> On Fri, 3 May 2019, Petr Mladek wrote:
> 
> > kobject_init() always succeeds and sets the reference count to 1.
> > It allows to always free the structures via kobject_put() and
> > the related release callback.
> > 
> > Note that the custom kobject state handling was used only
> > because we did not know that kobject_put() can and actually
> > should get called even when kobject_init_and_add() fails.
> > 
> > The patch should not change the existing behavior.
> 
> Pity that the changelog does not describe the change from 
> kobject_init_and_add() to two-stage kobject init (separate kobject_init() 
> and kobject_add()).
> 
> Petr changed it, because now each member of new dynamic lists (created in 
> klp_init_patch_early()) is initialized with kobject_init(), so we do not 
> have to worry about calling kobject_put() (this is slightly different from 
> kobj_added).
> 
> It would also be possible to retain kobject_init_and_add() and move it to 
> klp_init_patch_early(), but it would be uglier in my opinion.

kobject_init_and_add() is only there for the "simple" use cases.
There's no problem with doing the two-stage process on your own like
this, that's exactly what it is there for :)

thanks,

greg k-h