My machine crashed with KDevelop running, and after rebooting it won't start, saying:
Failed to lock the session, probably it is already active in another running instance
However I definitely do not have it running anywhere.
How can I clear up whatever kind of lock it created and failed to clean up after itself?
You can manually remove any KDevelop lock files via:
The accepted answer did nothing for me, however I didn't reboot my PC to try to fix the problem.
What worked for me was this:
After killing all instances of kdevelop, I could start it again, and pick a session.