Re: Notifier chains are unsafe

[Andi Kleen]

Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> 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.

-Andi
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