netdev - Re: BUG: soft lockup detected on CPU#0! (2.6.18.2 plus hacks)

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Message-ID: <459AEE33.7080702@candelatech.com>
Date:	Tue, 02 Jan 2007 15:43:47 -0800
From:	Ben Greear <greearb@...delatech.com>
To:	David Stevens <dlstevens@...ibm.com>
CC:	jarkao2@...pl, NetDev <netdev@...r.kernel.org>
Subject: Re: BUG: soft lockup detected on CPU#0!  (2.6.18.2 plus hacks)

David Stevens wrote:
> I've looked at this a little too -- it'd be nice to know who holds
> the write lock.
> 
> I see ip_mc_destroy_dev() is bouncing through the lock for
> each multicast address, though it starts at the beginning of
> the list each time. I don't see a problem with it, but it'd be
> simpler if it acquired the write lock once, grabbed and nulled
> the list, released the lock and then called igmp_group_dropped()
> & ip_ma_put() on each address from the local list copy.
> 
> Are you destroying/creating interfaces or doing a lot of multicasting at
> the time? How many group memberships do you have?

Lots and lots of interfaces were being created...at least 200 mac-vlans (out-of tree patch
somewhat similar to 802.1q vlans.)  The avahi-daemon process was running, and it appears
to be adding a multicast to each interface.  It was spewing failure messages in /var/log/messages,
probably because it can't handle so many interfaces.

Other than that, there is no (known) multicast traffic being generated.

This bug was reported to me by a user in Australia, and we have not yet
attempted to recreate this locally, so I am not certain exactly what it
takes to trigger this bug.

Thanks,
Ben

> 
>                                         +-DLS

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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