Arduino Multithreading Broken w/r/t Upload

What steps will reproduce the problem?
1. Upload a sketch to a programmer that isn't responding
2. Watch Arduino IDE spin its wheels indefinitely complaining that it can't 
upload the sketch b/c programmer isn't responding, or timed-out, or device 
isn't configured...it doesn't really matter
3.  Cannot cancel the attempted upload.  Have to wrestle with disconnecting, 
resetting, and re-trying until it works.

What is the expected output? What do you see instead?
It looks like the multithreading architecture in the _entire IDE_ is broken, 
but this bug report is more specific than that.  The thread that handles 
uploads should be interruptable and a cancel button should exist on the UI.

What version of the Arduino software are you using? On what operating
system?  Which Arduino board are you using?
Latest released 9/1/2012.  Arduino MEGA.

Please provide any additional information below.
Does the multithreading architecture in this app work such that each editor 
window knows which threads it owns and spawned?  If not, has the product really 
made it out of beta?

Original issue reported on code.google.com by fbeach...@gmail.com on 1 Sep 2012 at 7:17

Merged into: #585

dj0tt / arduino

Arduino Multithreading Broken w/r/t Upload #1026