I recently started using Eclipse on my Mac instead of my old WinXP Machine. I moved my workspace to a shared drive (smb://), but could not open my existing workspace. I received the error: “Workspace in use or cannot be created, choose a different one”.
There was no instance of eclipse accessing that workspace, but I found a .lock file workspace/.metadata/.lock. After manually removing the .lock file, I would restart Eclipse but it would still complain and re-write the .lock file back to the folder.
A local workspace worked just fine, so the problem is exclusive to using a workspace from a mounted filesystem. A quick search for NFS eclipse workspace turned up a way to alter the way file locking is done.
I edited the eclipse.ini file in Eclipse.app/Contents/MacOS, and added the following:
Once I added that startup option, eclipse was able to use the mounted workspace.