[Bug 447852] Re: WARNING: at /build/buildd/linux-2.6.31/arch/x86/kernel/apic/apic.c:247 native_apic_write_dummy+0x33/0x40()

[TJ]

Experienced the same here and traced it to the kernel incorrectly
thinking that lapic is disabled by the BIOS when there is no such option
(in BIOS). The upstream bug-report suggests that commit 48b1fddbb100a
may be responsible.

I've found the workaround is to add "lapic" (use Local Advanced
Programmable Interrupt Controller) to the kernel boot options. That
requires you to edit "/etc/default/grub" (with superuser privileges) and
add the option to GRUB_CMDLINE_LINUX:

GRUB_CMDLINE_LINUX="lapic"

Then update the grub configuration:

$ sudo update-grub

Reboot and the lapic should be used. Check dmesg to be sure:

$ grep -i apic /var/log/dmesg
[    0.000000] Using APIC driver default
[    0.000000] Local APIC disabled by BIOS -- reenabling.
[    0.000000] Found and enabled local APIC!
[    0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-2.6.31-14-generic root=UUID=4930abd5-48d4-4bf5-996e-ea96df9a2d95 ro lapic quiet splash
-----

$ uname -a
Linux mythbuntu 2.6.31-14-generic #48-Ubuntu SMP Fri Oct 16 14:04:26 UTC 2009 i686 GNU/Linux

----- cpuinfo -----
$ cat /proc/cpuinfo
processor	: 0
vendor_id	: AuthenticAMD
cpu family	: 6
model		: 6
model name	: AMD Athlon(TM) XP1800+
stepping	: 2
cpu MHz		: 1544.739
cache size	: 256 KB
fdiv_bug	: no
hlt_bug		: no
f00f_bug	: no
coma_bug	: no
fpu		: yes
fpu_exception	: yes
cpuid level	: 1
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow up
bogomips	: 3089.47
clflush size	: 32
power management: ts
-----

----- dmesg  with default boot configuration -----
[    0.000000] Local APIC disabled by BIOS -- you can enable it with "lapic"
[    0.000000] APIC: disable apic facility
...
[    0.002171] CPU: L1 I Cache: 64K (64 bytes/line), D cache 64K (64 bytes/line)
[    0.002175] CPU: L2 Cache: 256K (64 bytes/line)
[    0.002183] mce: CPU supports 4 MCE banks
[    0.002212] Performance Counters: AMD PMU driver.
[    0.002219] ------------[ cut here ]------------
[    0.002239] WARNING: at /build/buildd/linux-2.6.31/arch/x86/kernel/apic/apic.c:247 native_apic_write_dummy+0x33/0x40()
[    0.002244] Hardware name: System Name
[    0.002246] Modules linked in:
[    0.002253] Pid: 0, comm: swapper Not tainted 2.6.31-14-generic #48-Ubuntu
[    0.002257] Call Trace:
[    0.002273]  [<c014518d>] warn_slowpath_common+0x6d/0xa0
[    0.002279]  [<c011d7e3>] ? native_apic_write_dummy+0x33/0x40
[    0.002285]  [<c011d7e3>] ? native_apic_write_dummy+0x33/0x40
[    0.002291]  [<c01451d5>] warn_slowpath_null+0x15/0x20
[    0.002297]  [<c011d7e3>] native_apic_write_dummy+0x33/0x40
[    0.002305]  [<c010dcec>] perf_counters_lapic_init+0x2c/0x30
[    0.002315]  [<c0795aff>] init_hw_perf_counters+0x159/0x21c
[    0.002321]  [<c0795746>] identify_boot_cpu+0x21/0x23
[    0.002326]  [<c07958c8>] check_bugs+0xb/0xe9
[    0.002337]  [<c078e8c3>] start_kernel+0x2dc/0x2ec
[    0.002342]  [<c078e406>] ? unknown_bootoption+0x0/0x1ab
[    0.002348]  [<c078e07c>] i386_start_kernel+0x7c/0x83
[    0.002364] ---[ end trace a7919e7f17c0a725 ]---
...
[    0.031243] weird, boot CPU (#0) not listed by the BIOS.
[    0.031246] SMP motherboard not detected.
[    0.031251] Local APIC not detected. Using dummy APIC emulation.


** Changed in: linux (Ubuntu)
       Status: Invalid => Confirmed

-- 
WARNING: at /build/buildd/linux-2.6.31/arch/x86/kernel/apic/apic.c:247 native_apic_write_dummy+0x33/0x40()
https://bugs.launchpad.net/bugs/447852
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