Re: [PATCH] wireless extensions: play with netns

Johannes Berg [off-list ref] writes:

On Wed, 2009-06-17 at 16:54 -0700, Eric W. Biederman wrote:

quoted

quoted

Subject: net: make namespace iteration possible under RCU

We already call rcu_barrier(), so all we need to take
care of is using proper RCU list add/del primitives.

This of course gives you a network namespace that can be found by for_each_net rcu
while the per net exit functions are running.  I think that opens up to races
that I don't want to think about.

Indeed. Can we move the rcu_barrier() up? Or we could insert a
synchronize_rcu() (which is sufficient for rcu_read_lock) before the
exit functions are run?

I don't think we can move the barrier.   But adding an extra synchronize_rcu
should be fine.  We are talking about the slowest of the slow paths here.
It is so slow it even gets it's own kernel thread.

Eric
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