Need some help to debug a freeze on 2.6.11

Need some help to debug a freeze on 2.6.11

[Ehud Shabtai]

I'm running Linux on my laptop and it sometimes freezes (about once a
week). The only thing which seems to work when it's stuck is SysRq (I
can reboot with SysRq+O), however, I'm in X and I don't have a serial
port on my laptop so I can't see any of the outputs of the SysRq
options.

After a reboot I don't see anything in my logs about the crash.

Can anyone suggest how to get some information about my freeze?

Re: Need some help to debug a freeze on 2.6.11

[Alexander Nyberg]

> I'm running Linux on my laptop and it sometimes freezes (about once a
> week). The only thing which seems to work when it's stuck is SysRq (I
> can reboot with SysRq+O), however, I'm in X and I don't have a serial
> port on my laptop so I can't see any of the outputs of the SysRq
> options.
> 
> After a reboot I don't see anything in my logs about the crash.
> 
> Can anyone suggest how to get some information about my freeze?

Sounds like a job for Documentation/networking/netconsole.txt



started by Ingo Molnar <mingo@redhat.com>, 2001.09.17
2.6 port and netpoll api by Matt Mackall <mpm@selenic.com>, Sep 9 2003

Please send bug reports to Matt Mackall <mpm@selenic.com>

This module logs kernel printk messages over UDP allowing debugging of
problem where disk logging fails and serial consoles are impractical.

It can be used either built-in or as a module. As a built-in,
netconsole initializes immediately after NIC cards and will bring up
the specified interface as soon as possible. While this doesn't allow
capture of early kernel panics, it does capture most of the boot
process.

It takes a string configuration parameter "netconsole" in the
following format:


netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]

   where
        src-port      source for UDP packets (defaults to 6665)
        src-ip        source IP to use (interface address)
        dev           network interface (eth0)
        tgt-port      port for logging agent (6666)
        tgt-ip        IP address for logging agent
        tgt-macaddr   ethernet MAC address for logging agent (broadcast)

Examples:

 linux netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc

  or

 insmod netconsole netconsole=@/,@10.0.0.2/

Built-in netconsole starts immediately after the TCP stack is
initialized and attempts to bring up the supplied dev at the supplied
address.

The remote host can run either 'netcat -u -l -p <port>' or syslogd.

WARNING: the default target ethernet setting uses the broadcast
ethernet address to send packets, which can cause increased load on
other systems on the same ethernet segment.

NOTE: the network device (eth1 in the above case) can run any kind
of other network traffic, netconsole is not intrusive. Netconsole
might cause slight delays in other traffic if the volume of kernel
messages is high, but should have no other impact.

Netconsole was designed to be as instantaneous as possible, to
enable the logging of even the most critical kernel bugs. It works
from IRQ contexts as well, and does not enable interrupts while
sending packets. Due to these unique needs, configuration can not
be more automatic, and some fundamental limitations will remain:
only IP networks, UDP packets and ethernet devices are supported.

Re: Need some help to debug a freeze on 2.6.11

[Jesper Juhl]

On Mon, 18 Apr 2005, Alexander Nyberg wrote:

> > I'm running Linux on my laptop and it sometimes freezes (about once a
> > week). The only thing which seems to work when it's stuck is SysRq (I
> > can reboot with SysRq+O), however, I'm in X and I don't have a serial
> > port on my laptop so I can't see any of the outputs of the SysRq
> > options.
> > 
> > After a reboot I don't see anything in my logs about the crash.
> > 
> > Can anyone suggest how to get some information about my freeze?
> 
> Sounds like a job for Documentation/networking/netconsole.txt
> 
or Documentation/serial-console.txt

-- 
Jesper

Re: Need some help to debug a freeze on 2.6.11

[Jesper Juhl]

On Mon, 18 Apr 2005, Jesper Juhl wrote:

> On Mon, 18 Apr 2005, Alexander Nyberg wrote:
> 
> > > I'm running Linux on my laptop and it sometimes freezes (about once a
> > > week). The only thing which seems to work when it's stuck is SysRq (I
> > > can reboot with SysRq+O), however, I'm in X and I don't have a serial
> > > port on my laptop so I can't see any of the outputs of the SysRq
> > > options.
> > > 
> > > After a reboot I don't see anything in my logs about the crash.
> > > 
> > > Can anyone suggest how to get some information about my freeze?
> > 
> > Sounds like a job for Documentation/networking/netconsole.txt
> > 
> or Documentation/serial-console.txt
> 
Console on line printer would also be an option.

-- 
Jesper

Re: Need some help to debug a freeze on 2.6.11

[Ehud Shabtai]

On 4/18/05, Jesper Juhl <juhl-lkml@dif.dk> wrote:
> On Mon, 18 Apr 2005, Jesper Juhl wrote:
> 
> > On Mon, 18 Apr 2005, Alexander Nyberg wrote:
> >
> > > Sounds like a job for Documentation/networking/netconsole.txt
> > >
> > or Documentation/serial-console.txt
> >
> Console on line printer would also be an option.

I don't have any printer port cables, so I guess I prefer to try netconsole.

I'm using wireless lan (Intel's ipw2100), would netconsole work on
wlan interface?
As an alternative, can I configure netconsole for my ethernet port and
only really connect it, after I get the freeze?

Thanks for your help.

Re: Need some help to debug a freeze on 2.6.11

[Alexander Nyberg]

> > > > Sounds like a job for Documentation/networking/netconsole.txt
> > > >
> > > or Documentation/serial-console.txt
> > >
> > Console on line printer would also be an option.
> 
> I don't have any printer port cables, so I guess I prefer to try netconsole.
> 
> I'm using wireless lan (Intel's ipw2100), would netconsole work on
> wlan interface?

Not sure, can't comment on it...

> As an alternative, can I configure netconsole for my ethernet port and
> only really connect it, after I get the freeze?

Yep, this will work well.

Re: Need some help to debug a freeze on 2.6.11

[Denis Vlasenko]

On Monday 18 April 2005 13:56, Ehud Shabtai wrote:
> On 4/18/05, Jesper Juhl <juhl-lkml@dif.dk> wrote:
> > On Mon, 18 Apr 2005, Jesper Juhl wrote:
> > 
> > > On Mon, 18 Apr 2005, Alexander Nyberg wrote:
> > >
> > > > Sounds like a job for Documentation/networking/netconsole.txt
> > > >
> > > or Documentation/serial-console.txt
> > >
> > Console on line printer would also be an option.
> 
> I don't have any printer port cables, so I guess I prefer to try netconsole.
> 
> I'm using wireless lan (Intel's ipw2100), would netconsole work on
> wlan interface?

That depends on how far ipw2100 is into 'softmac' land.
That is, if it uses host CPU for some of it's functions,
it may be inoperative.

Wired net have more chances of working.

> As an alternative, can I configure netconsole for my ethernet port and
> only really connect it, after I get the freeze?

UDP packets will be long gone at the time you plug cable in.
--
vda

Re: Need some help to debug a freeze on 2.6.11

[Ehud Shabtai]

On 4/18/05, Denis Vlasenko <vda@ilport.com.ua> wrote:
> On Monday 18 April 2005 13:56, Ehud Shabtai wrote:
> > As an alternative, can I configure netconsole for my ethernet port and
> > only really connect it, after I get the freeze?
> 
> UDP packets will be long gone at the time you plug cable in.

I will probably lose the oops message, but won't I be able to use
SysRq to get some hints about the problem?

Anyway, which SysRq keys should help me debug the problem?