In theory, waiters can be lost in Mutex

[djspiewak]

If a waiter is notified at the exact moment that it is canceled, it's possible for that wake-up to be lost, which can leave the overall mutex in an inconsistent state.

[armanbilge]

I'm not sure if this is all theory, we still have the unexplained non-deterministic Skunk hanging.

[djspiewak]

The Skunk hanging isn't consistent with a failure in Mutex of this nature. The heap dump you gave me from the Skunk failure is internally inconsistent w.r.t. WSTP state. A Mutex failure in this fashion would have resulted in an entirely normal WSTP in a quiescent state, which isn't what we see.

[armanbilge]

The heap dump I gave you wasn't from Skunk at all :) that was experimental polling system stuff hanging in FS2.

I narrowed down the Skunk issues to Mutex in typelevel/skunk#852 (comment).

[durban]

Definitely not theory, see #3555 at an attempt to fix.