Thomas Graf <tg...@suug.ch> wrote:
> On 07/13/15 at 10:11pm, Cong Wang wrote:
> > Caused by:
> >
> > commit 21e4902aea80ef35afc00ee8d2abdea4f519b7f7
> > Author: Thomas Graf <tg...@suug.ch>
> > Date: Fri Jan 2 23:00:22 2015 +0100
> >
> > netlink: Lockless lookup with RCU grace period in socket release
> >
> > Defers the release of the socket reference using call_rcu() to
> > allow using an RCU read-side protected call to rhashtable_lookup()
> >
> > This restores behaviour and performance gains as previously
> > introduced by e341694 ("netlink: Convert netlink_lookup() to use
> > RCU protected hash table") without the side effect of severely
> > delayed socket destruction.
> >
> > Signed-off-by: Thomas Graf <tg...@suug.ch>
> > Signed-off-by: David S. Miller <da...@davemloft.net>
> >
> >
> > We can't hold mutex lock in a rcu callback, perhaps we could
> > defer the mmap ring cleanup to a workqueue.
>
> The socket should be dead at this point. It might be simpler to
> add a netlink_release_ring() function which doesn't require
> locking at all. It would also get rid of all the special handling
> for closing vs. non-closing.
Do you know of any users of mmap'd netlink?
Support for this was never added to libmnl; given the fact that netlink
mmap doesn't have any advantages vs. socket interface i'd just revert it
(or mark CONFIG_NETLINK_MMAP broken -- although I don't see
how the unconditional copy on tx could ever be avoided).
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