A couple of months back I started randomly experiencing thread locks when I started up Intellij which was resulting my IDE being totally unresponsive after loading.

 SEVERE - #c.i.o.a.WriteAction - Must not start write action from within read action in the other thread - 
    deadlock is coming java.lang.Throwable: Must not start write action from within read action in 
    the other thread - deadlock is coming at 
    com.intellij.openapi.diagnostic.Logger.error(Logger.java:376) 

The cause seemed the be this ominous warning, deadlock is coming! It was not kidding either. No response from the IDE, it rendered the UI and locked up.

After removing the snap install and a good deal of manual re-installing, I finally decided to seek out the configuration files and started altering things. But, none of this turned out to be enough to put an end to the thread locks.

After a bit of spelunking through Intellij support info I found the details of the config file locations along with info on how to manually delete the full install including all support files etc. Not wanting to have to reconfigure my personal preferences, I started the likely culprit, the cache! Caching in the IDE has a history of trouble, to the point they have introduced a wonderful, multi-step cache clean up tool to run, of course you need the UI to respond!

Sure enough, deleting the entirety of ~/.cache/JetBrains/<product><version> solved the problem! I literally did an rm -rf ~/.cache/JetBrains/<product><version> and restarted! And back to work!

Here's the list of install locations on Linux for when this needs to be cleaned up again. (Other OS locations are in the link mentioned above)

    ~/.config/JetBrains/<product><version>
    ~/.cache/JetBrains/<product><version>
    ~/.local/share/JetBrains/<product><version>

Just substitue in the latest version you have. Also, in theory you can delete all the old version and clear up some space as wel!

Extra NOTE: Also on Linux the default install location for a manual install is /opt/idea-IC-* the asterisk is for the release version.

Other useful links: Install Intellij

Photo/3D model Credit: CC Image by h2odragon on Printables I will be printing my own copy of this soon!