Re: Lockdep rtnl_mutex and genl_mutex circular dependency

[Johannes Berg <johannes@sipsolutions.net>]

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On Thu, 2009-02-19 at 18:31 -0800, Luis R. Rodriguez wrote:
> Just running 'iw list' a few times I got this. I have a few patches on
> top of wl, but this doesn't seem to be related to those.

I see what's going on, it's the genetlink change, the code is:

        if (nlh->nlmsg_flags & NLM_F_DUMP) {
                if (ops->dumpit == NULL)
                        return -EOPNOTSUPP;

                genl_unlock();
                err = 0;
                if (family->pre_dumpit)
                        err = family->pre_dumpit();
                if (!err)
                        err = netlink_dump_start(genl_sock, skb, nlh,
                                                 ops->dumpit, ops->done);
                if (family->post_dumpit)
                        family->post_dumpit();
                genl_lock();  
                return err;
        }

pre_dumpit does rtnl_lock(), and netlink_dump_start() will re-do
genl_lock(), so here we end up with a dependency of rtnl -> genl. But
in the non-dump path, we do the pre_doit() with genl held, getting
genl -> rtnl. We thus have to change the genetlink change, patch coming
in a minute.

johannes

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