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SubjectRe: Notifier chains are unsafe
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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
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Chandra Seetharaman | Be careful what you choose....
- sekharan@us.ibm.com | .......you may get it.
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