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From: Petr Mladek <pmladek@suse.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Tobin C. Harding" <tobin@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
	Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 5/5] livepatch: Do not manually track kobject initialization
Date: Thu, 2 May 2019 09:30:44 +0200	[thread overview]
Message-ID: <20190502073044.bfzugymrncnaajxe@pathway.suse.cz> (raw)
In-Reply-To: <20190502071232.GB16247@kroah.com>

On Thu 2019-05-02 09:12:32, Greg Kroah-Hartman wrote:
> On Thu, May 02, 2019 at 12:31:42PM +1000, Tobin C. Harding wrote:
> > Currently we use custom logic to track kobject initialization.  Recently
> > a predicate function was added to the kobject API so we now no longer
> > need to do this.
> > 
> > Use kobject API to check for initialized state of kobjects instead of
> > using custom logic to track state.
> > 
> > Signed-off-by: Tobin C. Harding <tobin@kernel.org>
> > ---
> >  include/linux/livepatch.h |  6 ------
> >  kernel/livepatch/core.c   | 18 +++++-------------
> >  2 files changed, 5 insertions(+), 19 deletions(-)
> > 
> > @@ -626,7 +626,7 @@ static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
> >  		list_del(&obj->node);
> >  
> >  		/* Might be called from klp_init_patch() error path. */
> > -		if (obj->kobj_added) {
> > +		if (kobject_is_initialized(&obj->kobj)) {
> >  			kobject_put(&obj->kobj);
> >  		} else if (obj->dynamic) {
> >  			klp_free_object_dynamic(obj);
> 
> Same here, let's not be lazy.
> 
> The code should "know" if the kobject has been initialized or not
> because it is the entity that asked for it to be initialized.  Don't add
> extra logic to the kobject core (like the patch before this did) just
> because this one subsystem wanted to only write 1 "cleanup" function.

We use kobject for a mix of statically and dynamically defined
structures[*]. And we misunderstood the behavior of kobject_init().

Anyway, the right solution is to call kobject_init()
already in klp_init_patch_early() for the statically
defined structures and in klp_alloc*() for the dynamically
allocated ones. Then we could simply call kobject_put()
every time.

Tobin, this goes deeper into the livepatching code that
you probably expected. Do you want to do the above
suggested change or should I prepare the patch?

Anyway, thanks for working on this.


[*] Yes, we know that kobject was not designed for
    static structures. We even tried to use them but
    there was a lot of extra code with not a big benefit.

Best Regards,
Petr

  reply	other threads:[~2019-05-02  7:30 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-02  2:31 [RFC PATCH 0/5] kobject: Add and use init predicate Tobin C. Harding
2019-05-02  2:31 ` [RFC PATCH 1/5] livepatch: Fix kobject memleak Tobin C. Harding
2019-05-02  7:22   ` Greg Kroah-Hartman
2019-05-02  8:46   ` Petr Mladek
2019-05-02  2:31 ` [RFC PATCH 2/5] kobject: Remove docstring reference to kset Tobin C. Harding
2019-05-02  7:20   ` Greg Kroah-Hartman
2019-05-02  2:31 ` [RFC PATCH 3/5] kobject: Fix kernel-doc comment first line Tobin C. Harding
2019-05-02  7:20   ` Greg Kroah-Hartman
2019-05-02  7:38   ` Johan Hovold
2019-05-02  8:25     ` Tobin C. Harding
2019-05-02  8:39       ` Johan Hovold
2019-05-03  1:40         ` Tobin C. Harding
2019-05-03  1:46           ` Randy Dunlap
2019-05-03 12:23             ` Jonathan Corbet
2019-05-03  7:56           ` Johan Hovold
2019-05-03  8:05             ` Petr Mladek
2019-05-06 23:00             ` Tobin C. Harding
2019-05-07  9:38               ` Johan Hovold
2019-05-02  2:31 ` [RFC PATCH 4/5] kobject: Add kobject initialized predicate Tobin C. Harding
2019-05-02  2:31 ` [RFC PATCH 5/5] livepatch: Do not manually track kobject initialization Tobin C. Harding
2019-05-02  7:12   ` Greg Kroah-Hartman
2019-05-02  7:30     ` Petr Mladek [this message]
2019-05-02  7:42       ` Greg Kroah-Hartman
2019-05-02  8:31       ` Tobin C. Harding
2019-05-02  8:51         ` Petr Mladek
2019-05-02 11:42 ` [RFC PATCH 0/5] kobject: Add and use init predicate Miroslav Benes

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