Panic after update from r347896 to r347950: panic: insanity vmem 0xffffffff81d7c840

This was fairly late in the transition from single- to multi-user mode:
the NICs had been probed; em0 was determined (correctly) to have no
link, but the wireless NIC (wlan0) hadn't associated to the AP yet.

I have placed copies of the dump and a couple of screenshots in
http://www.catwhisker.org/~david/FreeBSD/head/r347950/

Just before the panic message, there's:

.....overwrapped tags
	0xffffffff81d7cc70: 0 0, 5(cursor)
	0xfffff800040086c8: fffffe0c1052c000 8000000, 3(free)

and then we get to:
panic: insanity vmem 0xffffffff81d7c840


Unread portion of the kernel message buffer:

__curthread () at /usr/src/sys/amd64/include/pcpu.h:246
246             __asm("movq %%gs:%P1,%0" : "=r" (td) : "n" (OFFSETOF_CURTHREAD));
(kgdb) #0  __curthread () at /usr/src/sys/amd64/include/pcpu.h:246
#1  doadump (textdump=0) at /usr/src/sys/kern/kern_shutdown.c:383
#2  0xffffffff8049884b in db_dump (dummy=<optimized out>, 
    dummy2=<optimized out>, dummy3=<unavailable>, dummy4=<unavailable>)
    at /usr/src/sys/ddb/db_command.c:574
#3  0xffffffff80498619 in db_command (last_cmdp=<optimized out>, 
    cmd_table=<optimized out>, dopager=1) at /usr/src/sys/ddb/db_command.c:481
#4  0xffffffff80498394 in db_command_loop ()
    at /usr/src/sys/ddb/db_command.c:534
#5  0xffffffff8049b53f in db_trap (type=<optimized out>, code=<optimized out>)
    at /usr/src/sys/ddb/db_main.c:252
#6  0xffffffff80bc9acc in kdb_trap (type=3, code=0, tf=<optimized out>)
    at /usr/src/sys/kern/subr_kdb.c:692
#7  0xffffffff80fde7d1 in trap (frame=0xfffffe0c185ab810)
    at /usr/src/sys/amd64/amd64/trap.c:619
#8  <signal handler called>
#9  kdb_enter (why=0xffffffff81252ef5 "panic", msg=<optimized out>)
    at /usr/src/sys/kern/subr_kdb.c:479
#10 0xffffffff80b80c5a in vpanic (fmt=<optimized out>, ap=<optimized out>)
    at /usr/src/sys/kern/kern_shutdown.c:885
#11 0xffffffff80b809d3 in panic (
    fmt=0xffffffff81c75d38 <cnputs_mtx> "\226\216!\201\377\377\377\377")
    at /usr/src/sys/kern/kern_shutdown.c:823
#12 0xffffffff80be7fd3 in vmem_check (
    vm=0xffffffff81d7c840 <transient_arena_storage>)
    at /usr/src/sys/kern/subr_vmem.c:1766
#13 vmem_periodic (unused=<optimized out>, pending=<optimized out>)
    at /usr/src/sys/kern/subr_vmem.c:768
#14 0xffffffff80bdcd8c in taskqueue_run_locked (queue=0xfffff80009e33500)
    at /usr/src/sys/kern/subr_taskqueue.c:467
#15 0xffffffff80bddd08 in taskqueue_thread_loop (arg=<optimized out>)
    at /usr/src/sys/kern/subr_taskqueue.c:773
#16 0xffffffff80b40044 in fork_exit (
    callout=0xffffffff80bddc80 <taskqueue_thread_loop>, 
    arg=0xffffffff81e95000 <taskqueue_thread>, frame=0xfffffe0c185abac0)
    at /usr/src/sys/kern/kern_fork.c:1058
#17 <signal handler called>
(kgdb) 


[that last copy/pasted from core.txt.1].

I noticed nothing peculiar while (briefly) running r347896 (built
yesterday evening & smoke-tested: booted to multi-user mode; wlan0
associated to the expected AP at the time; X11 (xdm) came up, and
I was able to login, ssh to home -- the usual stuff).

The above link should be functional (but slow -- residential ADSL);
it has:

albert(11.3-P)[8] ls -lT
total 42849
-rw-r--r--  1 david  wheel    301534 May 18 05:18:26 2019 console_0.jpg
-rw-r--r--  1 david  wheel    311923 May 18 05:18:26 2019 console_1.jpg
-rw-r--r--  1 david  staff    156926 May 18 05:07:13 2019 core.txt.1
-rw-r--r--  1 david  staff     37080 May 18 05:07:13 2019 core.txt.1.gz
-rw-r--r--  1 david  staff  56590336 May 18 05:23:15 2019 vmcore.1.gz
albert(11.3-P)[9] 

Peace,
david
-- 
David H. Wolfskill				david_at_catwhisker.org
One wonders just who benefits from Trump's trade war with China.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.