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Date: Mon, 28 Apr 2008 19:27:59 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: Linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: umount(/proc) after CLONE_NEWNS in 2.6.25?
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On Mon, Apr 28, 2008 at 09:30:13PM +0400, Michael Tokarev wrote:
> [pid 6308] clone(child_stack=0xbfc9de94, flags=CLONE_NEWNS|SIGCHLD) = 6309
> [pid  6309] execve("/usr/sbin/umount", ["umount", "-n", "/proc"])
> ...
> [pid  6309] oldumount("/proc")          = -1 EBUSY (Device or resource busy)
> umount: /proc: device is busy
>
> Yes, various NAMESPACEs are enabled (i'm trying to experiment with
> those).
>
> Is it intentional?

It's very odd.  Could you bisect that down to offending changeset or
at least narrow the things down to -rc<something>?  I'm going down right
now, so won't be able to look into that until tonight...