Review request for 6693490

[Xueming Shen]

looks good, approved.

Alan Bateman wrote:
>
> 6693490: (se) select throws "File exists" IOException under load (lnx)
>
> Sherman, we've chatted about this issue so you will probably want to 
> review. It's a race between registration (or re-registration) and 
> close. Registrations are queued so that they come into effect at the 
> next select (as required by the spec) but if the channel is pre-closed 
> just before it is added to epoll then it possible that the socketpair, 
> used in the closing mechanism, gets registered with epoll.  Once that 
> happens it creates the conditions to cause a Selector spin, and where 
> the file descriptor is recycled for a new SelectableChannel, then 
> registration will fail with IOException "file exists". The fix is to 
> remove from epoll before the channel is killed and to skip pending 
> updates for closed channels (as these can result in re-registration). 
> To avoid any side effects with cancellation the deregister also purges 
> pending updates for the channel. Thanks to Serge Baranov, Robert 
> Larsen, Peter van Rensburg, Richard Ridgway, Greg Wilkins and others 
> for testing this fix, or preliminary versions of.
>
> The webrev is here:
>  http://cr.openjdk.java.net/~alanb/6693490/webrev.00
>
> Thanks,
> -Alan.