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Scenario: I'm copying a couple of large files from a DVD onto my desktop (Windows 7 Pro, in case that matters). After a while I realize that it is going to take too long time, and I press "cancel". The copy dialog changes and says "Canceling...", and then nothing happens for a long time -- several minutes, long enough for my patience to run out.

Why does it take time at all to "cancel" a copy-operation? What is the OS doing or waiting for?

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It's un-copying. On NTFS that involves some work. – Daniel R Hicks Oct 13 '12 at 12:06
Why? What does it do? – JesperE Oct 13 '12 at 12:20
@artistoex - "Post the source code"? This isn't Stack Overflow, why should there be any source code in this question? – ChrisF Oct 13 '12 at 13:54
@artistoex: This isn't code-related. It's with the Windows OS. I've observed this on Windows Vista & 7. Just a question though... Do you use Windows anyway? – Alex Essilfie Oct 13 '12 at 15:47
@artistoex: Why would you need the source code when you can read the assembly? And since when is it problematic to draw conclusions from observing behavior? – Oliver Salzburg Oct 13 '12 at 17:30

Most people would give an uneducated explanation to this, which is why I'm not going to explain this.

You should see this for yourself, Process Monitor allows you to see in detail what I/O is happening! This allows you to confirm whether it's doing something like "uncopying", whether the virus scanner is part of the lengthy cancellation and so on; try filtering down to the source and destination path such that you don't get a lot of irrelevant information.

I can't / won't copy any results at the moment; so, it is left as an exercise to the interested reader...

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But how will you distinguish copy from uncopy? That's my bet: The OS it is still copying. The UI cannot cancel the copy action all by it self. It has to wait for the OS to invoke the callback routine. Meanwhile it just shows 'Deleting...' – artistoex Oct 16 '12 at 12:32
@artistoex: These are different I/O operations and are thus easily distinguishable. – Tom Wijsman Oct 16 '12 at 13:07
really? What kind of I/O operations are they? – artistoex Oct 16 '12 at 15:50
@TomWijsman -- Maybe you could look for us, since you know what to look for. – Daniel R Hicks Oct 17 '12 at 11:56
@DanielRHicks: Seems like you're not interested at all, since you won't take a look for yourself. Process Monitor does not work on Gentoo Linux as far as I know; but well, I already know this out of experience but yet you are the one that's non-believing and actually trying out the application is much better than attempting to believe any random statement made on the subject even if it were a copy and paste from the application in question. Don't be lazy and give it a go yourself... Stack Exchange is about learning, if I need to do your homework then you'll not learn a thing. ;) – Tom Wijsman Oct 17 '12 at 15:24

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