panic in AcpiOsGetTimer during boot.

Hi,

I get the KASSERT panic in AcpiOsGetTimer() while booting a recent (2 day old)
kernel. When I delete the KASSERT(), the kernel boots and seems to work ok.
(This is the AcpiOsGetTimer() in sys/dev/acpica/Osd/OsdSchedule.c. There also
 seems to be one of these functions under contrib.)

Here is my dmesg after boot, if it helps indicate why this is called when "cold"
is still set. (I've marked where the dmesg ends when it Panics if the KASSERT()
is enabled.)

dmesg after booting:
Copyright (c) 1992-2017 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
	The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 12.0-CURRENT #1: Sun Oct  1 09:48:42 EDT 2017
    root_at_nfsv4-newerlap.rick.home:/sub1/sys.headsep30/amd64/compile/GENERIC amd64
FreeBSD clang version 3.7.0 (tags/RELEASE_370/final 246257) 20150906
WARNING: WITNESS option enabled, expect reduced performance.
VT(vga): resolution 640x480
CPU: Intel(R) Core(TM) i7-3610QM CPU _at_ 2.30GHz (2294.84-MHz K8-class CPU)
  Origin="GenuineIntel"  Id=0x306a9  Family=0x6  Model=0x3a  Stepping=9
  Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
  Features2=0x7fbae3bf<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM,PCID,SSE4.1,SSE4.2,x2APIC,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
  AMD Features=0x28100800<SYSCALL,NX,RDTSCP,LM>
  AMD Features2=0x1<LAHF>
  Structured Extended Features=0x281<FSGSBASE,SMEP,ERMS>
  XSAVE Features=0x1<XSAVEOPT>
  VT-x: PAT,HLT,MTF,PAUSE,EPT,UG,VPID
  TSC: P-state invariant, performance statistics
real memory  = 17179869184 (16384 MB)
avail memory = 16518905856 (15753 MB)
Event timer "LAPIC" quality 600
ACPI APIC Table: <_ASUS_ Notebook>
FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs
FreeBSD/SMP: 1 package(s) x 4 core(s) x 2 hardware threads
random: unblocking device.
arc4random: no preloaded entropy cache
ioapic0 <Version 2.0> irqs 0-23 on motherboard
SMP: AP CPU #1 Launched!
SMP: AP CPU #3 Launched!
SMP: AP CPU #7 Launched!
SMP: AP CPU #6 Launched!
SMP: AP CPU #4 Launched!
**** dmesg ends here when in KASSERT() panics.
SMP: AP CPU #5 Launched!
SMP: AP CPU #2 Launched!
Timecounter "TSC-low" frequency 1147419696 Hz quality 1000
random: entropy device external interface
netmap: loaded module
[ath_hal] loaded
module_register_init: MOD_LOAD (vesa, 0xffffffff80f779d0, 0) error 19
random: registering fast source Intel Secure Key RNG
random: fast provider: "Intel Secure Key RNG"
kbd1 at kbdmux0
nexus0
vtvga0: <VT VGA driver> on motherboard
cryptosoft0: <software crypto> on motherboard
acpi0: <_ASUS_ Notebook> on motherboard
acpi_ec0: <Embedded Controller: GPE 0x19, ECDT> port 0x62,0x66 on acpi0
acpi0: Power Button (fixed)
cpu0: <ACPI CPU> on acpi0
cpu1: <ACPI CPU> on acpi0
cpu2: <ACPI CPU> on acpi0
cpu3: <ACPI CPU> on acpi0
cpu4: <ACPI CPU> on acpi0
cpu5: <ACPI CPU> on acpi0
cpu6: <ACPI CPU> on acpi0
cpu7: <ACPI CPU> on acpi0
hpet0: <High Precision Event Timer> iomem 0xfed00000-0xfed003ff on acpi0
Timecounter "HPET" frequency 14318180 Hz quality 950
Event timer "HPET" frequency 14318180 Hz quality 550
atrtc0: <AT realtime clock> port 0x70-0x77 irq 8 on acpi0
atrtc0: Warning: Couldn't map I/O.
atrtc0: registered as a time-of-day clock, resolution 1.000000s
Event timer "RTC" frequency 32768 Hz quality 0
attimer0: <AT timer> port 0x40-0x43,0x50-0x53 irq 0 on acpi0
Timecounter "i8254" frequency 1193182 Hz quality 0
Event timer "i8254" frequency 1193182 Hz quality 100
Timecounter "ACPI-fast" frequency 3579545 Hz quality 900
acpi_timer0: <24-bit timer at 3.579545MHz> port 0x408-0x40b on acpi0
pcib0: <ACPI Host-PCI bridge> port 0xcf8-0xcff on acpi0
pci0: <ACPI PCI bus> on pcib0
pcib1: <ACPI PCI-PCI bridge> irq 16 at device 1.0 on pci0
pci1: <ACPI PCI bus> on pcib1
vgapci0: <VGA-compatible display> port 0xe000-0xe07f mem 0xf6000000-0xf6ffffff,0xf0000000-0xf3ffffff,0xf4000000-0xf5ffffff irq 16 at device 0.0 on pci1
vgapci0: Boot video device
hdac0: <NVIDIA GF110 HDA Controller> mem 0xf7080000-0xf7083fff irq 17 at device 0.1 on pci1
xhci0: <Intel Panther Point USB 3.0 controller> mem 0xf7300000-0xf730ffff irq 16 at device 20.0 on pci0
xhci0: 32 bytes context size, 64-bit DMA
usbus0: waiting for BIOS to give up control
xhci0: Port routing mask set to 0xffffffff
usbus0 on xhci0
usbus0: 5.0Gbps Super Speed USB v3.0
pci0: <simple comms> at device 22.0 (no driver attached)
ehci0: <Intel Panther Point USB 2.0 controller> mem 0xf7318000-0xf73183ff irq 16 at device 26.0 on pci0
usbus1: EHCI version 1.0
usbus1 on ehci0
usbus1: 480Mbps High Speed USB v2.0
hdac1: <Intel Panther Point HDA Controller> mem 0xf7310000-0xf7313fff irq 22 at device 27.0 on pci0
pcib2: <ACPI PCI-PCI bridge> irq 16 at device 28.0 on pci0
pci2: <ACPI PCI bus> on pcib2
pcib3: <ACPI PCI-PCI bridge> irq 17 at device 28.1 on pci0
pci3: <ACPI PCI bus> on pcib3
iwn0: <Intel Centrino Advanced-N 6200> mem 0xf7200000-0xf7201fff irq 17 at device 0.0 on pci3
arc4random: no preloaded entropy cache
arc4random: no preloaded entropy cache
arc4random: no preloaded entropy cache
arc4random: no preloaded entropy cache
arc4random: no preloaded entropy cache
arc4random: no preloaded entropy cache
arc4random: no preloaded entropy cache
pcib4: <ACPI PCI-PCI bridge> irq 19 at device 28.3 on pci0
pci4: <ACPI PCI bus> on pcib4
alc0: <Atheros AR8151 v2.0 PCIe Gigabit Ethernet> port 0xd000-0xd07f mem 0xf7100000-0xf713ffff irq 19 at device 0.0 on pci4
alc0: 11776 Tx FIFO, 12032 Rx FIFO
alc0: Using 1 MSI message(s).
miibus0: <MII bus> on alc0
atphy0: <Atheros F1 10/100/1000 PHY> PHY 0 on miibus0
atphy0:  none, 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseT-FDX, 1000baseT-FDX-master, auto, auto-flow
alc0: Using defaults for TSO: 65518/35/2048
alc0: Ethernet address: 10:bf:48:23:08:56
ehci1: <Intel Panther Point USB 2.0 controller> mem 0xf7317000-0xf73173ff irq 23 at device 29.0 on pci0
usbus2: EHCI version 1.0
usbus2 on ehci1
usbus2: 480Mbps High Speed USB v2.0
isab0: <PCI-ISA bridge> at device 31.0 on pci0
isa0: <ISA bus> on isab0
ahci0: <Intel Panther Point AHCI SATA controller> port 0xf070-0xf077,0xf060-0xf063,0xf050-0xf057,0xf040-0xf043,0xf020-0xf03f mem 0xf7316000-0xf73167ff irq 19 at device 31.2 on pci0
ahci0: AHCI v1.30 with 6 6Gbps ports, Port Multiplier not supported
ahcich0: <AHCI channel> at channel 0 on ahci0
ahcich2: <AHCI channel> at channel 2 on ahci0
ahciem0: <AHCI enclosure management bridge> on ahci0
acpi_lid0: <Control Method Lid Switch> on acpi0
acpi_button0: <Sleep Button> on acpi0
acpi_tz0: <Thermal Zone> on acpi0
acpi_acad0: <AC Adapter> on acpi0
battery0: <ACPI Control Method Battery> on acpi0
atkbdc0: <Keyboard controller (i8042)> port 0x60,0x64 irq 1 on acpi0
atkbd0: <AT Keyboard> irq 1 on atkbdc0
kbd0 at atkbd0
atkbd0: [GIANT-LOCKED]
psm0: <PS/2 Mouse> irq 12 on atkbdc0
psm0: [GIANT-LOCKED]
psm0: model Generic PS/2 mouse, device ID 0
est0: <Enhanced SpeedStep Frequency Control> on cpu0