[Lguest] [PATCH 4/5] lguest: use KVM hypercalls

[Herbert Xu]

On Wed, Apr 15, 2009 at 07:18:44AM -0700, Eric W. Biederman wrote:
>
> So holding the reference only blocks us indefinitely in
> netdev_wait_allrefs, blocking the network namespace exit, and holding
> net_mutex indefinitely.

OK that's a killer because process A in my previous scenario can
kill the device itself and cause a dead-lock.

So how about this? We replace the dev destructor with our own that
doesn't immediately call free_netdev.  We only call free_netdev once
all tun fd's attached to the device have been closed.

This can be achieved by simply adding a counter to tun_struct.
We'd also change the async detach path to set a marker instead
of detaching.  That marker can then be checked in places like
tun_get.

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert at gondor.apana.org.au>
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