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Re: [PATCH] panic during unregister_netdevice()

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: [PATCH] panic during unregister_netdevice()
From: Krishna Kumar <kumarkr@xxxxxxxxxx>
Date: Wed, 5 Nov 2003 17:16:10 -0800
Cc: krkumar@xxxxxxxxxx, netdev@xxxxxxxxxxx, Stephen Hemminger <shemminger@xxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx



> If the loops runs once or twice that is not a bug, it is possible for
> processes to grab onto the device via rtnetlink queries and similar
> and we have to pause and potentially schedule to deal with that.

Yes. I guess rtnetlink_rcv() calls netdev_run_todo() to handle that case.

> The core problem is that we end up putting the device reference to
> zero a second time, and for that reason we should prevent it by
> holding onto a reference around the entire loop and wait for the
> refcount to drop to '1'.

That was my original intention, but won't a driver that calls
unregister_netdevice() followed by a free_netdev() still panic the
system ? Since the netdev_run_todo() can run after this is done and
derefernce the 'dev'. (Or is the refcount of the dev->kobject going
to be > 1 and hence not freed ? This class/object code is new to me).

Thanks,

- KK


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