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SubjectRe: MIPS panic in 2.6.39 (bisected to 7eaceaccab5f)
On 05/24/2011 09:39 AM, Ralf Baechle wrote:
> On Tue, May 24, 2011 at 01:55:47AM -0500, Rob Landley wrote:
>
>> You can reproduce this under qemu by grabbing:
>>
>> http://landley.net/aboriginal/downloads/binaries/system-image-mips.tar.bz2
>>
>> If you extract that tarball and ./run-emulator.sh it should boot
>> to a mips shell prompt. Now build your own vmlinux to replace the
>> kernel in there with (using the attached .config), and try again,
>> you should get a panic message something like:
>>
>> PID hash table entries: 512 (order: -1, 2048 bytes)
>> Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
>> Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
>> Primary instruction cache 2kB, VIPT, 2-way, linesize 16 bytes.
>> Primary data cache 2kB, 2-way, VIPT, no aliases, linesize 16 bytes
>> Writing ErrCtl register=00000000
>> Readback ErrCtl register=00000000
>> Memory: 125836k/127004k available (2172k kernel code, 1168k reserved, 507k data, 156k init, 0k highmem)
>> SLUB: Genslabs=9, HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
>> NR_IRQS:256
>> CPU 0 Unable to handle kernel paging request at virtual address 00000080, epc == 803a09b0, ra == 803a0990
>> Oops[#1]:
>> Cpu 0
>> $ 0 : 00000000 00000050 1bdc0001 00000000
>> $ 4 : 00000018 00000000 00000001 00000000
>> $ 8 : fffffff8 00000001 00000000 fffffffc
>> $12 : fffffffc 00000000 00000008 fffffffc
>> $16 : 803bce58 803bef35 803c0000 803c0000
>> $20 : 80380000 00000000 00000000 00000000
>> $24 : 00000000 00000000
>> $28 : 80382000 80383ec8 00000000 803a0990
>> Hi : 00000000
>> Lo : 00000000
>> epc : 803a09b0 arch_init_irq+0x38/0x15c
>> Not tainted
>> ra : 803a0990 arch_init_irq+0x18/0x15c
>> Status: 10000002 KERNEL EXL
>> Cause : 0080000c
>> BadVA : 00000080
>> PrId : 00019300 (MIPS 24Kc)
>> Process swapper (pid: 0, threadinfo=80382000, task=803855c0, tls=00000000)
>> Stack : 803a17d4 87804000 803bce58 803bef35 803c0000 803c0000 8039fac4 8039fac4
>> 00000000 803bce58 80380f04 0000004a 8039f454 00000000 803beee0 00000000
>> 00000000 00000000 00000000 00000000 00000000 80315f00 00000000 00000000
>> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>> ...
>> Call Trace:
>> [<803a09b0>] arch_init_irq+0x38/0x15c
>> [<8039fac4>] start_kernel+0x1f0/0x33c
>> [<80315f00>] kernel_entry+0x0/0x94
>>
>>
>> Code: 8c437048 3c021bdc 34420001 <ac620080> 24030001 3c02803c 080e827d ac437040 8c43701c
>>
>>
>> I bisected it the problem to commit
>> 7eaceaccab5f40bbfda044629a6298616aeaed50, but have no idea what
>> the actual bug is. (Other than "a null pointer dereference from
>> arch_init_irq", I just dunno _why_.)
>
> That commit just does not seem to be the answer.

It's possible my script misbisected it or found some other unrelated
issue, I can try bisecting again...

Yup, my earlier bisect got confused by a different bug. This specific
bug was introduced by:

af3a1f6f4813907e143f87030cde67a9971db533 is the first bad commit
commit af3a1f6f4813907e143f87030cde67a9971db533
Author: Ralf Baechle <ralf@linux-mips.org>
Date: Tue Mar 29 11:43:19 2011 +0200

MIPS: Malta: Fix GCC 4.6.0 build error

CC arch/mips/mti-malta/malta-init.o
arch/mips/mti-malta/malta-init.c: In function 'prom_init':
arch/mips/mti-malta/malta-init.c:196:6: error: variable 'result' set
but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

:040000 040000 58f11c3479ae15f2c4d0a3e7486c7aa4e1ca3e96
33ad31b666926e7090b5165b79773eee38b58229 M arch

And this time I checked out the commit, confirmed it had the problem,
did "git show | patch -p1 -R", rebuilt, and confirmed that the problem
was fixed.

Sorry Jens, my bad...

> Can you provide the kernel disassembly for the arch_init_irq() function?

803a0978 <arch_init_irq>:
803a0978: 27bdffe0 addiu sp,sp,-32
803a097c: afbf0018 sw ra,24(sp)
803a0980: 0c0e8a23 jal 803a288c <init_i8259_irqs>
803a0984: 00000000 nop
803a0988: 0c0e8a4e jal 803a2938 <mips_cpu_irq_init>
803a098c: 00000000 nop
803a0990: 3c028038 lui v0,0x8038
803a0994: 8c426ae0 lw v0,27360(v0)
803a0998: 1040000a beqz v0,803a09c4 <arch_init_irq+0x4c>
803a099c: 3c02803c lui v0,0x803c
803a09a0: 3c02803c lui v0,0x803c
803a09a4: 8c437048 lw v1,28744(v0)
803a09a8: 3c021bdc lui v0,0x1bdc
803a09ac: 34420001 ori v0,v0,0x1
803a09b0: ac620080 sw v0,128(v1)
803a09b4: 24030001 li v1,1
803a09b8: 3c02803c lui v0,0x803c
803a09bc: 080e827d j 803a09f4 <arch_init_irq+0x7c>
803a09c0: ac437040 sw v1,28736(v0)
803a09c4: 8c43701c lw v1,28700(v0)
803a09c8: 2402fffa li v0,-6
803a09cc: 1462000a bne v1,v0,803a09f8 <arch_init_irq+0x80>
803a09d0: 3c02803c lui v0,0x803c
803a09d4: 3c04bbc8 lui a0,0xbbc8
803a09d8: 34820110 ori v0,a0,0x110
803a09dc: 8c420000 lw v0,0(v0)
803a09e0: 3c03803c lui v1,0x803c
803a09e4: 7c420080 ext v0,v0,0x2,0x1
803a09e8: ac627040 sw v0,28736(v1)
803a09ec: 3c02803c lui v0,0x803c
803a09f0: ac447044 sw a0,28740(v0)
803a09f4: 3c02803c lui v0,0x803c
803a09f8: 8c43701c lw v1,28700(v0)
803a09fc: 2862fffa slti v0,v1,-6
803a0a00: 14400016 bnez v0,803a0a5c <arch_init_irq+0xe4>
803a0a04: 3c058038 lui a1,0x8038
803a0a08: 2862fffc slti v0,v1,-4
803a0a0c: 14400007 bnez v0,803a0a2c <arch_init_irq+0xb4>
803a0a10: 3c02803c lui v0,0x803c
803a0a14: 2462ffff addiu v0,v1,-1
803a0a18: 2c420002 sltiu v0,v0,2
803a0a1c: 10400010 beqz v0,803a0a60 <arch_init_irq+0xe8>
803a0a20: 24a56ae4 addiu a1,a1,27364
803a0a24: 080e8290 j 803a0a40 <arch_init_irq+0xc8>

And so on.

> Also, does the problem go away if you switch from CONFIG_MIPS_MT_SMP to
> CONFIG_MIPS_MT_DISABLED? The former is designed to run on all MIPS CPUs
> and on a non-MT enabled CPU core it should just disable MT and run happily
> anyway. I know there was work on MT support being done by Thiemo Seufer
> and I wonder if that ever made it into qemu and if so, if qemu gets MT
> right.

I switched to that config symbol and it made no difference.

Have you guys been able to reproduce the problem?

Rob


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