Re: Notifier chains are unsafe

[Andreas Kleen]

>
> On 26 Oct 2005, Andi Kleen wrote:
>
> > 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.
>
> I don't understand this comment. What point is there in avoiding a
> lock
> when the list is empty?
Â
It doesn't add locking overhead forÂa common case.
Â
> Did you mean that a lock should be taken only if
> the list _is_ empty?

No.

> > Better would be likely to use RCU.
>
> Note that the RCU documentation says RCU critical sections are not
> allowed
> to sleep.
Â
In this case it would be ok.

Â
-Andi

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