David Fowler ran into an issue with the Query Store process experiencing waits due to spinlocks:
We were enjoying a nice peaceful afternoon when we hear panicked shouting that a SQL Server had become unresponsive and the customers were unable to do anything.
We moseyed on down to the server in question to take a look at it. One thing stood out immediately, CPU was pegged out at 100% but SQL itself didn’t actually seem to be doing anything, transactions\second was on the floor. Unfortunately this happened a while back and I didn’t think to capture any graphs or metrics at the time so you’re just going to have to take my word for this.
The issue David ran into was subsequently fixed, making this a cautionary tale to keep those SQL Server instances patched.