Runaway process in Activity Monitor

QMy MacBook Pro 12-inch has occasionally run its fans full blast. When I checked in Activity Monitor, distnoted was using almost 100% of CPU. Why is that, and how to prevent it?

Adistnoted is a well-known culprit for doing this, and is part of macOS, not malicious. If it runs away like this, restart your Mac when you can.

If this happens repeatedly, install any outstanding macOS updates, then start it up in Safe mode by holding ß throughout startup. Leave it a minute to rebuild its caches, then restart in normal mode.

If this is triggered by a specific app, it’s hard to trace. It can occur when there are incorrect permissions set in your Home folder. Fixing that is more daunting, and requires Recovery mode. Details are at bit.ly/ mac354rprprm.

Identify the culprit in Activity Monitor, by sorting its list by % CPU. Here four copies of distnoted are behaving themselves.

Persistent problems may need you to follow Apple’s procedure to reset permissions, which is done in Recovery mode.