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Date:      Tue, 22 Oct 2002 09:46:54 -0400 (EDT)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Terry Lambert <tlambert2@mindspring.com>
Cc:        hackers@FreeBSD.org, Diego Wentz Antunes <devlware@terra.com.br>
Subject:   Re: Kernel Panic Problems
Message-ID:  <XFMail.20021022094654.jhb@FreeBSD.org>
In-Reply-To: <3DB46B19.EC096B5F@mindspring.com>

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On 21-Oct-2002 Terry Lambert wrote:
> Diego Wentz Antunes wrote:
>> >>     I have been experiencing  several kernel panics from differents
>> >> situations, since a ls to just boot the kernel.
>> >> I configured all the options in rc.conf to save the core dump from
>> >> memory to HD and some of the results are
>> >> here in the file panics. Above all I search at internet some information
>> >> to try to explain this recursive panics
>> >> and found that it could be some memory problem. Is there a way to make a
>> >> hard test with memory?
>> >>    I'm uncertainty if it is the memory because the PC stayed turned on
>> >> for 6 days without any problem!
>> >>    Any comments will be welcome!
> 
> Panic #1:
> ---
>#0  dumpsys () at ../../kern/kern_shutdown.c:487
> 487             if (dumping++) {
> (kgdb) where
>#0  dumpsys () at ../../kern/kern_shutdown.c:487
>#1  0xc0164d4b in boot (howto=256) at ../../kern/kern_shutdown.c:316
>#2  0xc0165189 in panic (fmt=0xc02ae96c "%s") at ../../kern/kern_shutdown.c:595
>#3  0xc02623ab in trap_fatal (frame=0xc3e8be4c, eva=0) at
> ../../i386/i386/trap.c:966
>#4  0xc0262059 in trap_pfault (frame=0xc3e8be4c, usermode=0, eva=0) at
> ../../i386/i386/trap.c:859
>#5  0xc0261bff in trap (frame={tf_fs = 16, tf_es = 16, tf_ds = 16, tf_edi =
> 671703040, tf_esi = 0, 
>         tf_ebp = 0, tf_isp = -1008157064, tf_ebx = -1008183320, tf_edx =
> -1087061161, tf_ecx = -1008183320, 
>         tf_eax = 0, tf_trapno = 12, tf_err = 0, tf_eip = 0, tf_cs = 8, tf_eflags
> = 66118, 
>         tf_esp = -1071632535, tf_ss = 8}) at ../../i386/i386/trap.c:458
> (kgdb) quit
> ---
> 
> Is this a full backtrace?  I don't see any way that the stack
> could have started with "trap_pfault"... it had to be running
> something to cause a page fault.

It's a fault from userland perhaps.

> Panic #2:
> ---
> ...
>#8  0xc0261bff in trap (frame={tf_fs = 16, tf_es = 16, tf_ds = 16, tf_edi =
> -1064400440, tf_esi = -1007800320, 
>       tf_ebp = -1007805296, tf_isp = -1007805336, tf_ebx = 47288, tf_edx =
> -1690778642, tf_ecx = 821789308, 
>       tf_eax = -56600120, tf_trapno = 12, tf_err = 0, tf_eip = -1071249494,
> tf_cs = 8, tf_eflags = 66070, 
>       tf_esp = -1064405504, tf_ss = 2606062}) at ../../i386/i386/trap.c:458
>#9  0xc02607aa in generic_bcopy ()
>#10 0xc0247c30 in scstart (tp=0xc0879b00) at ../../dev/syscons/syscons.c:1285
>#11 0xc017c1e4 in ttstart (tp=0xc0879b00) at ../../kern/tty.c:1401
>#12 0xc017ccb9 in ttwrite (tp=0xc0879b00, uio=0xc3ee1ed4, flag=8323073) at
> ../../kern/tty.c:1957
> ...
> ---
> 
> This one stops being possible at #9; specifically, there is no
> version of syscons.c that, in scstart, calls generic_bcopy()
> directly.  The only functions it calls directly are q_to_b(),
> which is a copy, but the function which does it is not static,
> and has a global definition, and therefore should show up in
> the stack trace.  Similarly, the sc_puts() is also called.
> 
> None of this really matches 4.4, 4.6, or -current syscons.c,
> so more information is needed, but it's unlikely that syscons
> has changed and changed back, so significantly.  You need to
> look at the code at dev/syscons/syscons.c:1285 in your own
> source tree, which seems to differ significantly from the source
> tree the rest of us are using.

generic_bcopy() is an asm function which may not have a full frame.
Thus, when gdb walks back over the stacktrace, it may skip the frame
that called generic_bcopy() and go to the previous frame.  ddb sometimes
does a better job with backtraces for some reason.

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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