linux-kernel - Re: [PATCH 04/24] sysfs: Normalize removing sysfs directories.

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Date:	Sat, 30 May 2009 15:59:55 +0200
From:	Kay Sievers <kay.sievers@...y.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	linux-kernel@...r.kernel.org,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-fsdevel@...r.kernel.org, Greg KH <greg@...ah.com>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 04/24] sysfs: Normalize removing sysfs directories.

On Sat, May 30, 2009 at 15:07, Eric W. Biederman <ebiederm@...ssion.com> wrote:

> My take is simply that a correct user has to wait until no one else
> can find the kobject before calling kobject_del.  At which point
> races are impossible, and it doesn't matter if sysfs_mutex is held
> across the entire operation.

We have circular references between kobjects in some "advanced" users.
We can not break the circle without calling _del() on one of the
objects involved, but at that time all of the objects are still
referenced by another object. Only a _del() will break the circle, and
result in a release of the objects involved. Not sure how that would
behave with this change?

Thanks,
Kay
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