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Re: [Xen-users] Badness in softirq.c / no modules loaded / related tonet

To: Andy Smith <andy@xxxxxxxxxxxxxx>
Subject: Re: [Xen-users] Badness in softirq.c / no modules loaded / related tonetwork interface
From: Steven Hand <Steven.Hand@xxxxxxxxxxxx>
Date: Mon, 30 May 2005 02:36:01 +0100
Cc: Steven.Hand@xxxxxxxxxxxx, xen-users@xxxxxxxxxxxxxxxxxxx
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>
>On Mon, May 30, 2005 at 02:12:14AM +0100, Steven Hand wrote:
>>
>> >Since upgrading from 2.6.10 / xen 2.0.5 to 2.6.11 / xen 2.0-testing
>> >25/05/05 I am also seeing the following in dom0 console output.
>> >
>> >kernel: Badness in local_bh_enable at kernel/softirq.c:140
>
>[...]
>
>> Hmm - are you using CONFIG_HIGHMEM? This seems to be the required
>> path and may have something to do with it (we've certainly seen
>> nothing like this on our own E1000 boxes).
>
>CONFIG_HIGHMEM4G=y
>CONFIG_HIGHMEM=y
>
>The machine currently has 2G and is unlikely to ever go above 4G.
>Do I need those settings?

If you want dom0 to be able to use the memory, yes. Not if you just 
want to share it e.g. as 3 x 640MB chunks between 3 domains...

Error path seems to be: 

udp_poll():1334 does spin_lock_irq() which disables interrupts (__cli()) 
then line 1336 does udp_checksum_complete() which calls skb_checksum() 
which calls local_bh_enable() which barfs if irqs are disabled. 

This only happens under CONFIG_HIGHMEM. 

However - at first look this seems like it should happen under vanilla
linux too ... so I may be missing something. Will take a more detailed 
look....

In the meantime you could try to see if you can reproduce w/out 
CONFIG_HIGHMEM...

cheers,

S.

p.s. what is the app that's doing UDP polling? may be able to 
     reproduce locally which would help...

 


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