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Date:	Tue, 02 Jan 2007 15:43:47 -0800
From:	Ben Greear <>
To:	David Stevens <>
CC:, NetDev <>
Subject: Re: BUG: soft lockup detected on CPU#0!  ( 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 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.


>                                         +-DLS

Ben Greear <>
Candela Technologies Inc

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