KIO: Mass Copy of Files from Different Sources to Different Destinations

[Dawit A.]

On Tuesday 08 September 2009 08:42:27 David Faure wrote:
> On Thursday 27 August 2009, Dawit A. wrote:
> > On Tuesday 25 August 2009 10:10:46 Dawit A. wrote:
> > > After going back and refamiliarizing myself with the scheduler code, I
> > > have no objection in principle to the patch.
> 
> And after more testing, I object to my own patch, now :-)

Now that is funny... 

> It can lead to deadlocks when a high-level job needs multiple subjobs;
> for instance KIO::file_copy() needs a Get and a Put job, and if only one
> of these gets scheduled and not the other one, it will take a "slot" in
> the scheduler for an indefinite amount of time; if another file_copy does
>  the same, those two jobs could just wait forever on each other.

Hmm... the question I have is why would the end that got scheduled stay in 
queue for an indefinite amount of time ? In other words why would this be a 
deadlock case ? Would the scheduled job not be serviced as soon as an ioslave 
becomes available ? Can you give an example of how to trigger this dead lock ? 
I suppose I can simply start copying files from remote locations (sftp/ftp) 
until the max instances limit is reached, no ?