I've had this occur many times before when cloning data on drives, but have just worked out what actually triggers the bug;

if a folder tree being copied by explorer contains a shortcut created by another system, that would not be valid on the current 8.1 system, upon explorer hitting said shortcut either the underlying COM Surrogate (dllhost) or the explorer process itself will get caught in an infinite task thread loop. While everything still responds correctly, the copy window will be permanently stuck on attempting to copy the shortcut file, you cant pause, cancel or close the window and must terminate the COM Surrogate instance for it to bail.

Code-wise I'd say it's attempting to read the shortcut as a folder, and as such then gets caught in retrying. Also note that either of the process instances will consume an entire logical CPU thread due to being stuck without a timed sleep.

- windows 8.1 pro x64 in use at times of bug occurring, managing data on drives from vista (32bit), 7 (64bit) and 8/8.1 (64bit pro) systems.

• Edited by Paul17041993 Monday, June 22, 2015 3:02 AM

The shortcut is an existing file created at some point by another system on it's own drive, said drive then being pulled out and a data copy being performed. Permissions are fine, already checked that.

Simply put there's a stage in the code that isn't responding correctly to an error state on a file copy, instead of giving the user an error and option to skip the file, the thread just loops itself.
Alternatively the code tries to access the shortcut like it were a directory, and getting in a retry loop with the same problem.

• Edited by Paul17041993 Wednesday, June 24, 2015 8:05 AM

Hi Paul,

Is there any error message or warning recorded in the Event Viewer(Event Viewer\Windows Logs\Application,System)?
Have you tried to use Process monitor to trace the copying process?

Here is a link for reference:
Using Microsoft Process Monitor to trace file-, rights- or registry related problems
http://www.exactsoftware.com/docs/docview.aspx?documentid=%7Ba252cb95-41c2-4c25-9d14-94ba74a3e9b2%7D&NoHeader=1&NoSubject=1

If it is possible, please share us the exact detailed steps to reproduce the issue. We will try to reproduce and troubleshoot it.

Best regards

Neither Explorer or DLLHost log anything on file copy/access errors, and as such there's nothing at all of any use in the event logs, it's not possible for a thread loop to be logged anyway unless it specifically has a monitor thread watching what the task thread is doing.

Though at one time I did perform a process dump of DLLHost (COM) at the time it was looped but forgot about uploading it until now;
http://1drv.ms/1S7NK8N

alternate full link;
https://onedrive.live.com/redir?resid=918DC61A06CB8DF9!310&authkey=!ALaO4gk_geIn5Fg&ithint=file%2cDMP

• Edited by Paul17041993 1 hour 59 minutes ago