From: Alan Stern <stern@rowland.harvard.edu>
To: Kay Sievers <kay.sievers@vrfy.org>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>,
Greg KH <greg@kroah.com>,
Kernel development list <linux-kernel@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Randy Dunlap <randy.dunlap@oracle.com>
Subject: Re: [PATCH] kobject: make sure kobj->ktype is set before kobject_init
Date: Thu, 29 Nov 2007 13:04:59 -0500 (EST) [thread overview]
Message-ID: <Pine.LNX.4.44L0.0711291259300.4712-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <1196356667.3118.16.camel@lov.site>
On Thu, 29 Nov 2007, Kay Sievers wrote:
> > > Sounds fine, maybe we should also pass the name along, so it will be
> > > obvious what happens here:
> > > int kobject_init(struct kobject *kobj, struct kobj_type *type, const char *fmt, ...)
> >
> > I don't know... Normally *_init() routines can't fail, but this could.
> > Then things like device_register() would run into trouble: The caller
> > wouldn't know whether a failure occurred before or after the
> > kobject_init() call, so it wouldn't know what sort of cleanup action
> > was needed: kfree() or device_put().
>
> But wouldn't device_register() do the kobject cleanup for you when it
> fails? Why would a caller of device_register() care about the state of
> the kobject?
Let's say device_register() calls device_init(), which calls
kobject_init(), which fails. Then there's no cleanup to do --
device_register() returns -ENOMEM or some such code and the caller has
to do the kfree().
Now let's say device_register() calls device_init(), which succeeds,
and then calls device_add(), which fails. To recover properly,
somebody then has to call device_put(). That "somebody" can't be the
original caller -- according to the previous paragraph the original
caller won't do anything but kfree(). So the "somebody" has to be
device_register() itself.
But the device_put() will call kobject_put(), which will invoke the
device's cleanup routine, which will deallocate the structure. Now the
original caller gets an error code (perhaps -ENOMEM again) but must
_not_ call kfree().
So what should the original caller do when an error occurs?
Alan Stern
next prev parent reply other threads:[~2007-11-29 18:05 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-27 23:02 [RFC] New kobject/kset/ktype documentation and example code Greg KH
2007-11-27 23:03 ` [RFC] sample kobject implementation Greg KH
2007-11-27 23:04 ` [RFC] Sample kset/ktype/kobject implementation Greg KH
2007-11-28 16:35 ` Cornelia Huck
2007-11-29 6:11 ` Greg KH
2007-11-29 9:39 ` Cornelia Huck
2007-11-29 20:39 ` Greg KH
2007-11-29 22:11 ` Alan Stern
2007-11-30 5:07 ` Dave Young
2007-11-30 5:57 ` Dave Young
2007-11-30 14:51 ` Alan Stern
2007-11-30 6:41 ` Greg KH
2007-11-27 23:10 ` [RFC] New kobject/kset/ktype documentation and example code Kyle McMartin
2007-11-27 23:29 ` Greg KH
2007-11-27 23:21 ` Frans Pop
2007-11-28 3:50 ` Jonathan Corbet
2007-11-29 5:46 ` Greg KH
2007-11-28 9:01 ` Cornelia Huck
2007-11-28 12:35 ` Kay Sievers
2007-11-28 15:52 ` Cornelia Huck
2007-11-28 16:03 ` Kay Sievers
2007-11-28 16:09 ` Cornelia Huck
2007-11-28 17:06 ` Greg KH
2007-11-28 19:18 ` Alan Stern
2007-11-29 10:12 ` Cornelia Huck
2007-11-29 15:47 ` Alan Stern
2007-11-29 16:28 ` Cornelia Huck
2007-11-29 16:55 ` Alan Stern
2007-11-29 17:52 ` Cornelia Huck
2007-11-29 5:59 ` Greg KH
2007-11-28 11:45 ` Cornelia Huck
2007-11-28 12:23 ` Kay Sievers
2007-11-28 15:48 ` Cornelia Huck
2007-11-28 15:57 ` Kay Sievers
2007-11-28 16:12 ` Cornelia Huck
2007-11-28 16:36 ` Kay Sievers
2007-11-28 16:51 ` Cornelia Huck
2007-11-28 17:00 ` Kay Sievers
2007-11-29 6:08 ` Greg KH
2007-11-29 7:50 ` Kay Sievers
2007-11-29 9:35 ` Cornelia Huck
2007-11-29 10:53 ` Kay Sievers
2007-11-29 6:02 ` Greg KH
2007-11-29 6:04 ` Greg KH
2007-11-29 9:41 ` Cornelia Huck
2007-11-28 19:03 ` Alan Stern
2007-11-28 19:28 ` Kay Sievers
2007-11-28 19:36 ` Alan Stern
2007-11-28 19:46 ` Kay Sievers
2007-11-28 20:42 ` [PATCH] kobject: make sure kobj->ktype is set before kobject_init Alan Stern
2007-11-28 20:52 ` Kay Sievers
2007-11-28 21:45 ` Greg KH
2007-11-28 22:00 ` Alan Stern
2007-11-28 22:38 ` Greg KH
2007-11-29 10:05 ` Cornelia Huck
2007-11-29 10:59 ` Kay Sievers
2007-11-29 11:48 ` Cornelia Huck
2007-11-29 15:54 ` Alan Stern
2007-11-29 16:04 ` Kay Sievers
2007-11-29 16:21 ` Cornelia Huck
2007-11-29 21:53 ` kobject_init rewrite Greg KH
2007-11-29 21:54 ` Greg KH
2007-11-30 9:31 ` Cornelia Huck
2007-11-29 22:16 ` Alan Stern
2007-11-29 22:24 ` Greg KH
2007-11-29 17:06 ` [PATCH] kobject: make sure kobj->ktype is set before kobject_init Alan Stern
2007-11-29 17:17 ` Kay Sievers
2007-11-29 18:04 ` Alan Stern [this message]
2007-11-29 18:33 ` Kay Sievers
2007-11-29 19:05 ` Alan Stern
2007-11-29 19:51 ` Kay Sievers
2007-11-29 20:09 ` Alan Stern
2007-11-29 20:19 ` Kay Sievers
2007-11-29 20:26 ` Kay Sievers
2007-11-30 9:30 ` Cornelia Huck
2007-11-29 6:18 ` [RFC] New kobject/kset/ktype documentation and example code Greg KH
2007-11-29 15:42 ` Alan Stern
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