The flow control and ticketing systems in theory sit above the locking hierarchy, but there are some exceptions to this rule, most notably multi-statement transactions.

This inversion of the locking order has been source of bugs in the past, such as SERVER-76834.

I am filing this ticket to request that we document somewhere the rules based on which we are certain that there are no deadlocks due to this inversion and possibly to add testing and/or invariants.
The testing that I am imagining is for example having a successful (albeit slow) concurrency run with a max ticket number of 1.