netconsole module cannot be removed

netconsole module cannot be removed

[Chuck Ebbert]

Trying to remove netconsole, rmmod goes into a tight loop with
100% CPU usage. It can't be killed with 'kill -9'. Shutdown
works, though. Kernel is 2.6.20 FC6 config, and I'm 99.9%
sure the module signing has nothing to do with this.

Re: netconsole module cannot be removed

[Stephen Hemminger]

On Mon, 26 Feb 2007 15:35:11 -0500
Chuck Ebbert <cebbert@redhat.com> wrote:

> Trying to remove netconsole, rmmod goes into a tight loop with
> 100% CPU usage. It can't be killed with 'kill -9'. Shutdown
> works, though. Kernel is 2.6.20 FC6 config, and I'm 99.9%
> sure the module signing has nothing to do with this.
> 

No it probably has to do with printing a message during module removal.

-- 
Stephen Hemminger <shemminger@linux-foundation.org>

Re: netconsole module cannot be removed

[Chuck Ebbert]

Stephen Hemminger wrote:
> On Mon, 26 Feb 2007 15:35:11 -0500
> Chuck Ebbert <cebbert@redhat.com> wrote:
> 
>> Trying to remove netconsole, rmmod goes into a tight loop with
>> 100% CPU usage. It can't be killed with 'kill -9'. Shutdown
>> works, though. Kernel is 2.6.20 FC6 config, and I'm 99.9%
>> sure the module signing has nothing to do with this.
>>
> 
> No it probably has to do with printing a message during module removal.
> 

Yeah that could explain it.

But when I load it after the network has started I can't get it to
output any kernel messages to the network interface, either. I'll
try to reproduce this on a vanilla kernel next...

Re: netconsole module cannot be removed

[Dave Jones]

On Mon, Feb 26, 2007 at 01:31:56PM -0800, Stephen Hemminger wrote:
 > On Mon, 26 Feb 2007 15:35:11 -0500
 > Chuck Ebbert <cebbert@redhat.com> wrote:
 > 
 > > Trying to remove netconsole, rmmod goes into a tight loop with
 > > 100% CPU usage. It can't be killed with 'kill -9'. Shutdown
 > > works, though. Kernel is 2.6.20 FC6 config, and I'm 99.9%
 > > sure the module signing has nothing to do with this.
 > > 
 > 
 > No it probably has to do with printing a message during module removal.

I just reproduced this, and something really spooky happened.
After echo t > /proc/sysrq-trigger, the 'rmmod' process doesn't
show up in the backtrace. Everything else is there though.
The process shows up in a regular 'ps', but not in the sysrq output.

Most bizarre.

		Dave

-- 
http://www.codemonkey.org.uk

Re: netconsole module cannot be removed

[Chuck Ebbert]

Stephen Hemminger wrote:
> On Mon, 26 Feb 2007 15:35:11 -0500
> Chuck Ebbert <cebbert@redhat.com> wrote:
> 
>> Trying to remove netconsole, rmmod goes into a tight loop with
>> 100% CPU usage. It can't be killed with 'kill -9'. Shutdown
>> works, though. Kernel is 2.6.20 FC6 config, and I'm 99.9%
>> sure the module signing has nothing to do with this.
>>
> 
> No it probably has to do with printing a message during module removal.
> 

Works fine in 2.6.19.5

Hangs in vanilla 2.6.20 in netpoll_cleanup()

Call trace: 
 flush_cpu_workqueue
 flush_workqueue
 cancel_rearming_delayed_workqueue
 netpoll_cleanup
 sys_delete_module

It varies, but is always in one of the first three functions when you
do alt-sysrq-p.