acpi_hpet0 gets found twice during boot: first attach fails, second succeeds

[Bruce Cran]

I noticed while scanning through my dmesg that acpi_hpet0 gets found 
twice during bootup: the first time it fails to attach because it never 
increments, but the second time around it works and is chosen as the 
primary timecounter:

acpi0: <HPQOEM SLIC-MPC> on motherboard
acpi0: [ITHREAD]
acpi0: Power Button (fixed)
Timecounter "ACPI-safe" frequency 3579545 Hz quality 850
acpi_timer0: <32-bit timer at 3.579545MHz> port 0x408-0x40b on acpi0
acpi_ec0: <Embedded Controller: GPE 0x3> port 0x62,0x66 on acpi0
acpi_hpet0: <High Precision Event Timer> iomem 0xfed00000-0xfed003ff on 
acpi0
acpi_hpet0: HPET never increments, disabling
device_attach: acpi_hpet0 attach returned 6
acpi_button0: <Power Button> on acpi0

Then a bit later:

battery0: <ACPI Control Method Battery> on acpi0
cpu0: <ACPI CPU> on acpi0
acpi_throttle0: <ACPI CPU Throttling> on cpu0
cpu1: <ACPI CPU> on acpi0
acpi_hpet0: <High Precision Event Timer> iomem 0xfed00000-0xfed003ff on 
acpi0
Timecounter "HPET" frequency 14318180 Hz quality 900

Is this expected?

-- 
Bruce Cran <cid:part1.07030001.01090502 at cran.org.uk>
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FreeBSD 8.0-CURRENT #2: Tue Dec 16 21:48:59 PST 2008
    brucec at tau.draftnet:/usr/obj/usr/src/sys/GENERIC
WARNING: WITNESS option enabled, expect reduced performance.
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: AMD Turion(tm) X2 Dual-Core Mobile RM-70 (1999.19-MHz K8-class CPU)
  Origin = "AuthenticAMD"  Id = 0x200f31  Stepping = 1
  Features=0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2,HTT>
  Features2=0x2001<SSE3,CX16>
  AMD Features=0xea500800<SYSCALL,NX,MMX+,FFXSR,RDTSCP,LM,3DNow!+,3DNow!>
  AMD Features2=0x131f<LAHF,CMP,SVM,ExtAPIC,CR8,Prefetch,OSVW,SKINIT>
  TSC: P-state invariant
  Cores per package: 2
usable memory = 4009422848 (3823 MB)
avail memory  = 3840131072 (3662 MB)
ACPI APIC Table: <HPQOEM SLIC-MPC>
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1
ioapic0: Changing APIC ID to 4
ioapic0 <Version 2.1> irqs 0-23 on motherboard
kbd1 at kbdmux0
acpi0: <HPQOEM SLIC-MPC> on motherboard
acpi0: [ITHREAD]
acpi0: Power Button (fixed)
Timecounter "ACPI-safe" frequency 3579545 Hz quality 850
acpi_timer0: <32-bit timer at 3.579545MHz> port 0x408-0x40b on acpi0
acpi_ec0: <Embedded Controller: GPE 0x3> port 0x62,0x66 on acpi0
acpi_hpet0: <High Precision Event Timer> iomem 0xfed00000-0xfed003ff on acpi0
acpi_hpet0: HPET never increments, disabling
device_attach: acpi_hpet0 attach returned 6
acpi_button0: <Power Button> on acpi0
pcib0: <ACPI Host-PCI bridge> port 0xcf8-0xcff on acpi0
pci0: <ACPI PCI bus> on pcib0
pcib1: <ACPI PCI-PCI bridge> at device 1.0 on pci0
pci1: <ACPI PCI bus> on pcib1
vgapci0: <VGA-compatible display> port 0x7000-0x70ff mem 0xc0000000-0xcfffffff,0xd2400000-0xd240ffff,0xd2300000-0xd23fffff irq 18 at device 5.0 on pci1
pci1: <multimedia, HDA> at device 5.1 (no driver attached)
pcib2: <ACPI PCI-PCI bridge> at device 4.0 on pci0
pci2: <ACPI PCI bus> on pcib2
pcib3: <ACPI PCI-PCI bridge> at device 5.0 on pci0
pci8: <ACPI PCI bus> on pcib3
pci8: <base peripheral> at device 0.0 (no driver attached)
pci8: <base peripheral, SD host controller> at device 0.2 (no driver attached)
pci8: <base peripheral> at device 0.3 (no driver attached)
pci8: <base peripheral> at device 0.4 (no driver attached)
pcib4: <ACPI PCI-PCI bridge> at device 6.0 on pci0
pci9: <ACPI PCI bus> on pcib4
ath0: <Atheros 5424/2424> mem 0xd1100000-0xd110ffff irq 18 at device 0.0 on pci9
ath0: [ITHREAD]
ath0: WARNING: using obsoleted if_watchdog interface
ath0: mac 14.2 phy 7.0 radio 10.2
pcib5: <ACPI PCI-PCI bridge> at device 7.0 on pci0
pci10: <ACPI PCI bus> on pcib5
re0: <RealTek 8101E/8102E/8102EL PCIe 10/100baseTX> port 0x2000-0x20ff mem 0xd1010000-0xd1010fff,0xd1000000-0xd100ffff irq 19 at device 0.0 on pci10
re0: Chip rev. 0x24800000
re0: MAC rev. 0x00200000
miibus0: <MII bus> on re0
rlphy0: <RTL8201L 10/100 media interface> PHY 1 on miibus0
rlphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
re0: Ethernet address: 00:1e:ec:f5:fd:4f
re0: [FILTER]
atapci0: <ATI AHCI controller> port 0x8038-0x803f,0x804c-0x804f,0x8030-0x8037,0x8048-0x804b,0x8010-0x801f mem 0xd2508000-0xd25083ff irq 22 at device 17.0 on pci0
atapci0: [ITHREAD]
atapci0: AHCI Version 01.10 controller with 6 ports PM supported
ata2: <ATA channel 0> on atapci0
ata2: [ITHREAD]
ata3: <ATA channel 1> on atapci0
ata3: [ITHREAD]
ata4: <ATA channel 2> on atapci0
ata4: [ITHREAD]
ata5: <ATA channel 3> on atapci0
ata5: [ITHREAD]
ata6: <ATA channel 4> on atapci0
ata6: [ITHREAD]
ata7: <ATA channel 5> on atapci0
ata7: [ITHREAD]
ohci0: <OHCI (generic) USB controller> mem 0xd2507000-0xd2507fff irq 16 at device 18.0 on pci0
ohci0: [GIANT-LOCKED]
ohci0: [ITHREAD]
usb0: OHCI version 1.0, legacy support
usb0: <OHCI (generic) USB controller> on ohci0
usb0: USB revision 1.0
uhub0: <ATI OHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb0
uhub0: 3 ports with 3 removable, self powered
ohci1: <OHCI (generic) USB controller> mem 0xd2506000-0xd2506fff irq 16 at device 18.1 on pci0
ohci1: [GIANT-LOCKED]
ohci1: [ITHREAD]
usb1: OHCI version 1.0, legacy support
usb1: <OHCI (generic) USB controller> on ohci1
usb1: USB revision 1.0
uhub1: <ATI OHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb1
uhub1: 3 ports with 3 removable, self powered
ehci0: <EHCI (generic) USB 2.0 controller> mem 0xd2508500-0xd25085ff irq 17 at device 18.2 on pci0
ehci0: [GIANT-LOCKED]
ehci0: [ITHREAD]
usb2: EHCI version 1.0
usb2: companion controllers, 3 ports each: usb0 usb1
usb2: <EHCI (generic) USB 2.0 controller> on ehci0
usb2: USB revision 2.0
uhub2: <ATI EHCI root hub, class 9/0, rev 2.00/1.00, addr 1> on usb2
uhub2: 6 ports with 6 removable, self powered
umass0: <PEAK III Flash Drive, class 0/0, rev 2.00/1.00, addr 2> on uhub2
ugen0: <SuYin HP Webcam, class 239/2, rev 2.00/1.00, addr 3> on uhub2
ohci2: <OHCI (generic) USB controller> mem 0xd2505000-0xd2505fff irq 18 at device 19.0 on pci0
ohci2: [GIANT-LOCKED]
ohci2: [ITHREAD]
usb3: OHCI version 1.0, legacy support
usb3: <OHCI (generic) USB controller> on ohci2
usb3: USB revision 1.0
uhub3: <ATI OHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb3
uhub3: 3 ports with 3 removable, self powered
ohci3: <OHCI (generic) USB controller> mem 0xd2504000-0xd2504fff irq 18 at device 19.1 on pci0
ohci3: [GIANT-LOCKED]
ohci3: [ITHREAD]
usb4: OHCI version 1.0, legacy support
usb4: <OHCI (generic) USB controller> on ohci3
usb4: USB revision 1.0
uhub4: <ATI OHCI root hub, class 9/0, rev 1.00/1.00, addr 1> on usb4
uhub4: 3 ports with 3 removable, self powered
ehci1: <EHCI (generic) USB 2.0 controller> mem 0xd2508400-0xd25084ff irq 19 at device 19.2 on pci0
ehci1: [GIANT-LOCKED]
ehci1: [ITHREAD]
usb5: EHCI version 1.0
usb5: companion controllers, 3 ports each: usb3 usb4
usb5: <EHCI (generic) USB 2.0 controller> on ehci1
usb5: USB revision 2.0
uhub5: <ATI EHCI root hub, class 9/0, rev 2.00/1.00, addr 1> on usb5
uhub5: 6 ports with 6 removable, self powered
pci0: <serial bus, SMBus> at device 20.0 (no driver attached)
atapci1: <ATI IXP700 UDMA133 controller> port 0x1f0-0x1f7,0x3f6,0x170-0x177,0x376,0x8000-0x800f irq 16 at device 20.1 on pci0
ata0: <ATA channel 0> on atapci1
ata0: [ITHREAD]
pci0: <multimedia, HDA> at device 20.2 (no driver attached)
isab0: <PCI-ISA bridge> at device 20.3 on pci0
isa0: <ISA bus> on isab0
pcib6: <ACPI PCI-PCI bridge> at device 20.4 on pci0
pci128: <ACPI PCI bus> on pcib6
acpi_acad0: <AC Adapter> on acpi0
acpi_lid0: <Control Method Lid Switch> on acpi0
acpi_tz0: <Thermal Zone> on acpi0
acpi_tz0: _HOT value is absurd, ignored (226.8C)
atrtc0: <AT realtime clock> port 0x70-0x71 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]
atkbd0: [ITHREAD]
psm0: <PS/2 Mouse> irq 12 on atkbdc0
psm0: [GIANT-LOCKED]
psm0: [ITHREAD]
psm0: model Generic PS/2 mouse, device ID 0
battery0: <ACPI Control Method Battery> on acpi0
cpu0: <ACPI CPU> on acpi0
acpi_throttle0: <ACPI CPU Throttling> on cpu0
cpu1: <ACPI CPU> on acpi0
acpi_hpet0: <High Precision Event Timer> iomem 0xfed00000-0xfed003ff on acpi0
Timecounter "HPET" frequency 14318180 Hz quality 900
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <16 virtual consoles, flags=0x300>
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
ppc0: cannot reserve I/O port range
Timecounters tick every 1.000 msec
ad4: 238475MB <Hitachi HTS543225L9A300 FBEOC44C> at ata2-master SATA300
acd0: DVDR <HL-DT-ST DVDRAM GSA-T50L/SC04> at ata5-master SATA150
GEOM_LABEL: Label for provider ad4s2 is ntfs/HP_RECOVERY.
SMP: AP CPU #1 Launched!
WARNING: WITNESS option enabled, expect reduced performance.
da0 at umass-sim0 bus 0 target 0 lun 0
da0: <PEAK III Flash Drive 0.00> Removable Direct Access SCSI-2 device 
da0: 40.000MB/s transfers
da0: 1967MB (4030463 512 byte sectors: 255H 63S/T 250C)
Trying to mount root from ufs:/dev/ad4s3a
lock order reversal:
 1st 0xffffff00014b5070 user map (user map) @ /usr/src/sys/vm/vm_map.c:3115
 2nd 0xffffff0004cfc270 ufs (ufs) @ /usr/src/sys/kern/vfs_subr.c:2079
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x81e
__lockmgr_args() at __lockmgr_args+0xca8
ffs_lock() at ffs_lock+0x8c
VOP_LOCK1_APV() at VOP_LOCK1_APV+0x9b
_vn_lock() at _vn_lock+0x47
vget() at vget+0x8b
vnode_pager_lock() at vnode_pager_lock+0x1d0
vm_fault() at vm_fault+0x1e2
trap_pfault() at trap_pfault+0x128
trap() at trap+0x51c
calltrap() at calltrap+0x8
--- trap 0xc, rip = 0x40014f, rsp = 0x7fffffffee70, rbp = 0x7fffffffee90 ---