/var/log/messages doesn't have crash info when kernel gets panic/oops/crash

[Dharmosoth Seetharam]

Hi,

I have experimented few things and results are below.

Case 1) echo 0 > /proc/sys/kernel/panic_on_oops
        When BUG/oops occurred it is able to log the diagnostics to /var/log/messages
        and then continue(not switching to dump-saving kernel).

        What I am looking is - I want both the things to be happen.
        that is - it should log the appropriate messages in /var/log/messsages and
        should be able to take kernel dump.

case 2) In general, When panic has occurred we won't log any type of messages in
        /var/log/messages ... am I right ?
        If KEXEC is enabled and dump-saving kernel is loaded then 
        will switch to it and save the kernel dump.

        I have added the dump_stack() function call in the panic() function 
        before calling crash_kexec with few seconds of delay. It is behaving 
        like randomly (ie. some time stack traces are logged in /var/log/messages and 
        not for rest of the time)

        What I am looking is - I want to log the  appropriate messages in /var/log/messages
        and then switch to dump-saving kernel.

case 3) In general, When die/nmi_die called we used to log the appropriate messages in /var/log/message
        and then saving kernel dump will be depends on KEXEC enable and loading dump-saving kernel.
        --- am I right ?
        
        I have added the delay in die() function with few seconds before calling crash_kexec()
        But I never seen messages logged in /var/log/messages, I can see those on serial console.

        Here also my intention is want both, ie. log the appropriate messages in /var/log/messages
        and then take the action as per KEXEC enabled.



Please advice me, What we can do to achieve those things.

Thanks for helping me here.


regards,
Seetharam





> -----Original Message-----
> From: nhorman at redhat.com
> Sent: Sat, 13 Jun 2009 14:07:36 -0400
> To: dseetharam at inbox.com
> Subject: Re: /var/log/messages doesn't have crash info when kernel gets
> panic/oops/crash
> 
> On Fri, Jun 12, 2009 at 11:01:35PM -0800, Dharmosoth Seetharam wrote:
>> 
>> Hi Neil,
>> 
>> Thanks for your quick reply.
>> 
>> What you have suggested is nice when we got/save crash dump (i.e vmcore)
>> What if we failed to save/capture vmcore info or vmcore is corrupted
>> etc. then we dont get any information
>> regarding the panic/crash/oops at anywhere?
>> 
> If the vmcore is corrupted to the point where makedumpfile can't extract
> the
> dmesg log, then its certain that syslog wouldn't have been able to write
> anything to /var/log/messages either.  As a last resort you can try run
> strings
> on the corrupted vmcore and see if the dmesg log is still in there
> somewhere.
> 
> If you forgot to capture the vmcore, theres not much more help I can give
> you,
> Im afraid.  You'll just have to make sure you capture it next time.  If
> you only
> need the backtrace, and don't want the rest of the vmcore, you can make
> kdump
> just run makedumpfile --dump-dmesg /proc/vmcore /var/log/oops.txt
> 
> Neil
> 


>> 
>> 
>> 
>> Thanks and Regards
>> 
>>  Seetharam
>> 
>> 
>>> -----Original Message-----
>>> From: nhorman at redhat.com
>>> Sent: Fri, 12 Jun 2009 16:05:13 -0400
>>> To: dseetharam at inbox.com
>>> Subject: Re: /var/log/messages doesn't have crash info when kernel gets
>>> panic/oops/crash
>>> 
>>> On Fri, Jun 12, 2009 at 01:25:49AM -0800, Dharmosoth Seetharam wrote:
>>>> Hi,
>>>> 
>>>> I have encounter a problem called /var/log/messages does not contain
>>>> any
>>>> information
>>>> on kernel crash dump.
>>>> 
>>>> Prior to enabling KEXEC we saw stack traces and bug info etc in
>>>> /var/log/messages.
>>>> After enabling KEXEC feature those info was missed.
>>>> 
>>>> How can we get those missed info in /var/log/messages even when KEXEC
>>>> feature is enabled.
>>>> 
>>>> Any help will appreciate.
>>>> 
>>> run crash on the resultant vmcore file that kexec can produce/save and
>>> get the
>>> dmesg log out of it.
>>> alternatively you can use makedumpfile with the --dump-dmesg log
>>> 
>>> Neil
>>> 
>>>> 
>>>> Thanks and Regards
>>>> Seetharam
>>>> 
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