Date: Mon, 21 Jul 2008 19:34:26 +0200
From: Cornelia Huck <cornelia.huck@de.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Jens Axboe <jens.axboe@oracle.com>, Greg K-H <greg@kroah.com>
Subject: Re: [PATCH] block: fix block_class iteration locking
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On Mon, 14 Jul 2008 20:50:57 +0900,
Tejun Heo <tj@kernel.org> wrote:

> > With your patch, you protect against adding/removing devices to/from
> > the class between _start and _stop. This wasn't done previously, and
> > won't be done with Greg's patches (which leaves in the
> > locking/unlocking of block_class_lock). Not sure if I'm missing
> > something here...
> 
> That's mostly the point of this patch.  It wasn't protected properly
> before.  It would be best if there's a safe iterator (maybe use klist?).

Hm, I don't see how a klist would help here since it still allows to
add/remove devices during walking the file.

What we need is more like a "lock/unlock the device list" operation and
a lockless iterator - that would give the same semantics as your patch.
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