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Re: One bug fixed, another found?

To: Linux-MIPS <linux-mips@oss.sgi.com>
Subject: Re: One bug fixed, another found?
From: Kunihiko IMAI <kimai@laser5.co.jp>
Date: Wed, 06 Feb 2002 23:06:57 +0900
In-reply-to: <NEBBLJGMNKKEEMNLHGAICEDFCFAA.mdharm@momenco.com>
References: <NEBBLJGMNKKEEMNLHGAICEDFCFAA.mdharm@momenco.com>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Wanderlust/2.4.0 (Rio) WEMI/1.13.7 (Shimada) CLIME/1.13.6 (中ノ庄) MULE XEmacs/21.1 (patch 14) (Cuyahoga Valley) (i386-vine-linux)
Hi,

I also got the Oops in same place.

My environment is:

        o board:        Pb1000 ( Au1000 eval. board )
        o kernel:       SGI version of 2.4.17
        o root fs:      nfs root
        o userland:     RedHat 7.1 got from SGI ftp site.

When rebuilding rpm package on the MIPS board, I also got error in
same place.

Today I compiled kernel with __wake_up_common not inline function, and
got same result.  And also made kgdb version.  I found that the line

        p = curr->task;

made the memory violation.  When trap occurs, gdb says

        curr = 0xfffffffc

So here is the place of memory violation.

At Thu, 31 Jan 2002 18:09:29 -0800,
Matthew Dharm wrote:

> Unable to handle kernel paging request at virtual address fffffffc,
> epc == 8010b
> 1ec, ra == 8010b19c
> $0 : 00000000 b0045400 00000000 00000000 00000017 802d51cc 92bdc000
> 93e7d120
> $8 : 92bdc000 b0045401 00000000 00000000 00000000 00000000 00000088
> 00000000
> $16: 00000000 b0045400 00000001 b0045401 802de998 802dad88 00000001
> 92ce1160
> $24: 00000000 2acce4e0                   92bdc000 92bddd68 92bddd68
> 8010b19c
> epc  : 8010b1ec    Not tainted
> Using defaults from ksymoops -t elf32-tradbigmips -a mips:3000
> Status: b0045402
> Cause : 80008008
> Process bladeenc (pid: 660, stackpage=92bdc000)
> Stack: 92bddd68 92bddd68 92bddd68 92bddd68 802df378 00000001 00000000
> 93ff8bf0
>        802df1fc 802df36c 000001d2 92bc4060 8012c588 8012c528 00001000
> 92bc4060
>        00000000 92bc4060 81018fc0 92ce1160 00000005 92bc4120 00001a55
> 93ff8bf0
>        92ce1160 0000001f 00001000 8012c180 81018fc0 92bc4120 00001a54
> 93ff8bec
>        80122aa0 80122af8 93f036c0 00000000 80170988 80170980 00000005
> 00001a50
>        92ce1160 ...
> Call Trace: [<8012c588>] [<8012c528>] [<8012c180>] [<80122aa0>]
> [<80122af8>] [<8
> 0170988>]
>  [<80170980>] [<801233ec>] [<8012372c>] [<8012377c>] [<80126198>]
> [<80123d80>]
>  [<80123c78>] [<801680dc>] [<8010703c>] [<8013290c>] [<80113158>]
> [<80106508>]
>  [<80106508>]
> Code: 12400004  00000000  8e100000 <5614ffcc> 8e05fffc  40016000
> 32730001  3421
> 0001  38210001
> 
> >>RA;  8010b19c <__wake_up+ec/198>
> >>PC;  8010b1ec <__wake_up+13c/198>   <=====
> Trace; 8012c588 <__alloc_pages+d0/21c>
> Trace; 8012c528 <__alloc_pages+70/21c>
> Trace; 8012c180 <_alloc_pages+20/2c>
> Trace; 80122aa0 <page_cache_read+a0/11c>
> Trace; 80122af8 <page_cache_read+f8/11c>
> Trace; 80170988 <nfs_updatepage+218/314>
> Trace; 80170980 <nfs_updatepage+210/314>
> Trace; 801233ec <generic_file_readahead+174/1ec>
> Trace; 8012372c <do_generic_file_read+24c/51c>
> Trace; 8012377c <do_generic_file_read+29c/51c>
> Trace; 80126198 <generic_file_write+558/828>
> Trace; 80123d80 <generic_file_read+94/1a0>
> Trace; 80123c78 <file_read_actor+0/74>
> Trace; 801680dc <nfs_file_read+cc/ec>
> Trace; 8010703c <handle_IRQ_event+80/f4>
> Trace; 8013290c <sys_read+d8/130>
> Trace; 80113158 <sys_time+18/5c>
> Trace; 80106508 <stack_done+1c/38>
> Trace; 80106508 <stack_done+1c/38>
> Code;  8010b1e0 <__wake_up+130/198>
> 00000000 <_PC>:
> Code;  8010b1e0 <__wake_up+130/198>
>    0:   12400004  beqz    s2,14 <_PC+0x14> 8010b1f4
> <__wake_up+144/198>
> Code;  8010b1e4 <__wake_up+134/198>
>    4:   00000000  nop
> Code;  8010b1e8 <__wake_up+138/198>
>    8:   8e100000  lw      s0,0(s0)
> Code;  8010b1ec <__wake_up+13c/198>   <=====
>    c:   5614ffcc  0x5614ffcc   <=====

This is MIPS2 code.  If you use objdump to disassemble, add
-m mips:4600 option to get correct mnemonic.

And the cause register says exception occurred in delay slot, so:

> Code;  8010b1f0 <__wake_up+140/198>
>   10:   8e05fffc  lw      a1,-4(s0)

The memory violation occurs here.

Registers dump says s0 = 00000000, memory access to 0xfffffffc occurs
here.

> Code;  8010b1f4 <__wake_up+144/198>
>   14:   40016000  mfc0    at,$12
> Code;  8010b1f8 <__wake_up+148/198>
>   18:   32730001  andi    s3,s3,0x1
> Code;  8010b1fc <__wake_up+14c/198>
>   1c:   34210001  ori     at,at,0x1
> Code;  8010b200 <__wake_up+150/198>
>   20:   38210001  xori    at,at,0x1

Thanks.
_._. __._  _ . ... _  .___ ._. _____ _... ._ _._ _.._. .____  _ . ... _

                                                          Kunihiko IMAI

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