From: Chandra Seetharaman <sekharan@us.ibm.com>
To: Andi Kleen <ak@suse.de>
Cc: Alan Stern <stern@rowland.harvard.edu>, linux-kernel@vger.kernel.org
Subject: Re: Notifier chains are unsafe
Date: Tue, 25 Oct 2005 17:01:51 -0700 [thread overview]
Message-ID: <1130284911.3586.152.camel@linuxchandra> (raw)
In-Reply-To: <p733bmp40yz.fsf@verdi.suse.de>
On Wed, 2005-10-26 at 01:43 +0200, Andi Kleen wrote:
> Alan Stern <stern@rowland.harvard.edu> writes:
>
> > 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!
>
> If you add locks to the reader make sure it is only taken
> if the list is non empty. Otherwise you will add unacceptable
> overhead to some fast paths.
>
> Better would be likely to use RCU.
RCU will be a problem if the registered notifiers need to block.
>
> -Andi
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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>
>
--
----------------------------------------------------------------------
Chandra Seetharaman | Be careful what you choose....
- sekharan@us.ibm.com | .......you may get it.
----------------------------------------------------------------------
next prev parent reply other threads:[~2005-10-26 0:01 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 [this message]
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
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