epoch callback panic

From: Peter Holm <pho_at_FreeBSD.org>
Date: Fri, 01 Apr 2022 17:07:45 UTC 
markj@ asked me to post this one:

panic: rw lock 0xfffff801bccb1410 not unlocked
cpuid = 4
time = 1648770125
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00e48a3d10
vpanic() at vpanic+0x17f/frame 0xfffffe00e48a3d60
panic() at panic+0x43/frame 0xfffffe00e48a3dc0
_rw_destroy() at _rw_destroy+0x35/frame 0xfffffe00e48a3dd0
in_lltable_destroy_lle_unlocked() at in_lltable_destroy_lle_unlocked+0x1a/frame 0xfffffe00e48a3df0
epoch_call_task() at epoch_call_task+0x13a/frame 0xfffffe00e48a3e40
gtaskqueue_run_locked() at gtaskqueue_run_locked+0xa7/frame 0xfffffe00e48a3ec0
gtaskqueue_thread_loop() at gtaskqueue_thread_loop+0xc2/frame 0xfffffe00e48a3ef0
fork_exit() at fork_exit+0x80/frame 0xfffffe00e48a3f30
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00e48a3f30
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---

Details @ https://people.freebsd.org/~pho/stress/log/log0275.txt

- Peter