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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: npiggin@kernel.dk, linux-fsdevel@vger.kernel.org
Subject: Re: [2.6.38] Deadlock between rename_lock and vfsmount_lock.
Date: Fri, 18 Mar 2011 11:06:03 +0000	[thread overview]
Message-ID: <20110318110603.GG22723@ZenIV.linux.org.uk> (raw)
In-Reply-To: <201103181959.CHC73937.SQOLJtVHOMFFOF@I-love.SAKURA.ne.jp>

On Fri, Mar 18, 2011 at 07:59:08PM +0900, Tetsuo Handa wrote:
> I established steps to reproduce.
> 
> On a 2.6.38 kernel built with CONFIG_SMP=y running on an SMP machine, run
> 
>   while :; do newns /sbin/pivot_root /proc/ /proc/sys/; done
> 
> on one terminal and run
> 
>   while :; do /bin/ls -l /proc/*/exe; done
> 
> on another terminal. (The "newns" is a program that unshares the mnt namespace
> before execve() using CLONE_NEWNS.)
> 
> Below patch releases/reacquires vfsmount_lock when rescheduling is required.
> ---
>  fs/dcache.c             |   15 ++++++++++++++-
>  fs/namespace.c          |    6 ++++++
>  include/linux/sched.h   |    2 ++
>  include/linux/seqlock.h |    4 ++++
>  4 files changed, 26 insertions(+), 1 deletion(-)

That's incredibly ugly.  I agree that the deadlock exists and needs to be
dealt with, but not that way.  _Strongly_ NAKed.  I'll see what I can come
up with, but that variant is not an option.

  reply	other threads:[~2011-03-18 11:06 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-03-16  8:54 [2.6.38] Possible deadlock at pivot_root? Tetsuo Handa
2011-03-17  5:01 ` [2.6.38] Deadlock between rename_lock and vfsmount_lock Tetsuo Handa
2011-03-18 10:59   ` Tetsuo Handa
2011-03-18 11:06     ` Al Viro [this message]
2011-03-18 11:54       ` Tetsuo Handa
2011-03-18 12:07       ` Al Viro
2011-03-18 12:13         ` Al Viro
2011-03-18 12:52         ` Al Viro
2011-03-18 13:18           ` Al Viro
2011-03-19  2:39             ` Tetsuo Handa
2011-03-23 23:00               ` Greg KH
2011-03-24  0:04                 ` Tetsuo Handa
2011-03-24  0:10                   ` Greg KH

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