lili93's session (#ardour) triggered this w/jackd 512fpp:
Drag/Drop copy a latent plugin from one track to another while rolling.
The GUI-thread as well as the auto-connect thread concurrently call
jack_recompute_total_latencies(). The auto-connect thread holds
a process lock while doing so. The GUI does not use any mutexes.
This randomly deadlocks in libjack.
backtrace: https://pastebin.com/6m3KGhWS