From: Keith Owens <kaos@ocs.com.au>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: Notifier chains are unsafe
Date: Wed, 26 Oct 2005 16:11:46 +1000 [thread overview]
Message-ID: <7908.1130307106@kao2.melbourne.sgi.com> (raw)
In-Reply-To: Your message of "Mon, 24 Oct 2005 16:48:58 -0400." <Pine.LNX.4.44L0.0510241634410.4448-100000@iolanthe.rowland.org>
On Mon, 24 Oct 2005 16:48:58 -0400 (EDT),
Alan Stern <stern@rowland.harvard.edu> wrote:
>Has anyone been bothered by the fact that notifier chains are not safe
>with regard to registration and unregistration while the chain is in use?
>The notifier_chain_register and notifier_chain_unregister routines have
>writelock protections, but the corresponding readlock is never taken!
>
>It shouldn't be hard to make this work safely, even allowing such things
>as notifier routines unregistering themselves as they run. The patch
>below contains an example implementation, showing one way to do it.
>
>But doing this correctly requires knowing how notifier chains are used.
>
> Are they always called in process context, with interrupts enabled?
>
> Or do some get called in interrupt context?
Register and unregister should only be called from contexts that can
sleep, although that may not be documented. notifier_call_chain() can
be called in any context, it must not take any locks.
prev parent reply other threads:[~2005-10-26 6:13 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-24 20:48 Notifier chains are unsafe Alan Stern
2005-10-25 16:59 ` Joe Seigh
2005-10-25 23:30 ` Chandra Seetharaman
2005-10-26 18:46 ` Alan Stern
2005-10-26 19:05 ` Andreas Kleen
2005-10-26 20:40 ` Alan Stern
2005-10-26 21:44 ` Andi Kleen
2005-10-26 23:20 ` Chandra Seetharaman
2005-10-27 1:17 ` Joe Seigh
2005-10-28 1:36 ` Chandra Seetharaman
2005-10-27 14:13 ` Alan Stern
2005-10-26 22:40 ` Chandra Seetharaman
2005-10-27 15:28 ` Alan Stern
2005-10-27 20:43 ` Chandra Seetharaman
2005-10-27 21:21 ` Alan Stern
2005-10-27 23:02 ` Chandra Seetharaman
2005-10-28 0:48 ` Keith Owens
2005-10-28 1:34 ` Chandra Seetharaman
2005-10-28 14:23 ` Alan Stern
2005-10-28 22:15 ` Chandra Seetharaman
2005-10-29 14:51 ` Alan Stern
2005-10-31 22:22 ` Chandra Seetharaman
2005-11-01 15:24 ` Alan Stern
2005-11-01 20:20 ` Chandra Seetharaman
2005-11-01 21:20 ` Alan Stern
2005-11-02 9:50 ` Keith Owens
2005-11-02 16:03 ` Alan Stern
[not found] ` <mailman.1130460600.30060.linux-kernel2news@redhat.com>
2005-10-28 4:35 ` Pete Zaitcev
2005-10-25 23:43 ` Andi Kleen
2005-10-26 0:01 ` Chandra Seetharaman
2005-10-26 17:11 ` Andreas Kleen
2005-10-27 2:46 ` Herbert Xu
2005-10-29 12:25 ` Joe Seigh
2005-10-26 6:11 ` Keith Owens [this message]
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