There is a deadlock when destroying VLANs after the epoch changes were made.

Thread 1:

epoch_block_handler_preempt() at epoch_block_handler_preempt+0x90/frame 0xfffffe00261b3970
ck_epoch_synchronize_wait() at ck_epoch_synchronize_wait+0x9d/frame 0xfffffe00261b39c0
epoch_wait_preempt() at epoch_wait_preempt+0x170/frame 0xfffffe00261b3a20
vlan_setmulti() at vlan_setmulti+0xb4/frame 0xfffffe00261b3a70
vlan_ioctl() at vlan_ioctl+0x83/frame 0xfffffe00261b3ad0
in6m_release_task() at in6m_release_task+0x32e/frame 0xfffffe00261b3b30
gtaskqueue_run_locked() at gtaskqueue_run_locked+0xf9/frame 0xfffffe00261b3b80
gtaskqueue_thread_loop() at gtaskqueue_thread_loop+0x88/frame 0xfffffe00261b3bb0
fork_exit() at fork_exit+0x84/frame 0xfffffe00261b3bf0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00261b3bf0

Thread 2:

sleepq_switch() at sleepq_switch+0x10d/frame 0xfffffe002bffd3f0
sleepq_wait() at sleepq_wait+0x43/frame 0xfffffe002bffd420
_sx_xlock_hard() at _sx_xlock_hard+0x4a6/frame 0xfffffe002bffd4c0
_sx_xlock() at _sx_xlock+0xc1/frame 0xfffffe002bffd500
in6_leavegroup() at in6_leavegroup+0x27/frame 0xfffffe002bffd520
in6_purgeaddr() at in6_purgeaddr+0xc2/frame 0xfffffe002bffd6a0
if_purgeaddrs() at if_purgeaddrs+0x11e/frame 0xfffffe002bffd750
if_detach_internal() at if_detach_internal+0x709/frame 0xfffffe002bffd7d0
if_detach() at if_detach+0x3d/frame 0xfffffe002bffd7f0
vlan_clone_destroy() at vlan_clone_destroy+0x21/frame 0xfffffe002bffd820
if_clone_destroyif() at if_clone_destroyif+0x175/frame 0xfffffe002bffd870
if_clone_destroy() at if_clone_destroy+0x205/frame 0xfffffe002bffd8c0
ifioctl() at ifioctl+0x582/frame 0xfffffe002bffd990
kern_ioctl() at kern_ioctl+0x2ba/frame 0xfffffe002bffd9f0
sys_ioctl() at sys_ioctl+0x15e/frame 0xfffffe002bffdac0
amd64_syscall() at amd64_syscall+0x28c/frame 0xfffffe002bffdbf0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe002bffdbf0
syscall (54, FreeBSD ELF64, sys_ioctl), rip = 0x80047b92a, rsp = 0x7fffffffe318, rbp = 0x7fffffffe330 ---