linux-kernel - Re: [PATCH 10/11] avoid kobject name conflict with different namespaces

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Date:	Fri, 09 May 2008 11:16:10 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Cornelia Huck <cornelia.huck@...ibm.com>
Cc:	ebiederm@...ssion.com (Eric W. Biederman),
	Greg KH <gregkh@...e.de>,
	Benjamin Thery <benjamin.thery@...l.net>,
	linux-kernel@...r.kernel.org, Tejun Heo <htejun@...il.com>,
	Al Viro <viro@....linux.org.uk>,
	Daniel Lezcano <dlezcano@...ibm.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Pavel Emelyanov <xemul@...nvz.org>, netdev@...r.kernel.org
Subject: Re: [PATCH 10/11] avoid kobject name conflict with different namespaces

Cornelia Huck <cornelia.huck@...ibm.com> writes:

> On Thu, 08 May 2008 12:28:19 -0700,
> ebiederm@...ssion.com (Eric W. Biederman) wrote:
>
>> Do you remember if we have ever sorted out the race between _move
>> and module unload/directory teardown at the sysfs level?
>
> Unfortunately I can't remember anything about this, do you have a
> pointer to the original discussion?

Ok the conversation was:
"[Bluez-devel] Oops involving RFCOMM and sysfs"
http://lkml.org/lkml/2007/12/28/87

Following the thread through it appears the bug was fixed
and it wasn't the race Al Viro was concerned about.
http://lkml.org/lkml/2008/1/9/59

And it looks like all of the symptoms have been corrected.
Yeah!

Which implies to me that kobject_move has the same locking
restrictions that kobject_rename has.  I.e. the upper level
better do what it takes to make the operation safe.

Which says that at least for now not worrying about the locking
between sysfs_move_dir/sysfs_rename_dir and sysfs_remove_dir is ok.
As we require the upper levels not to do that.

Which says that we may be able to figure out how to merge
sysfs_move_dir and sysfs_rename_dir.  It is still a nasty business
though.

Eric

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