netdev - Re: [PATCH 29/38] cls_flower: Convert handle

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Message-ID: <CAM_iQpXXKwKUhzU1wwXrXqwXSEq-OJ4diBhSuR04kitLKs=g0g@mail.gmail.com>
Date:   Sun, 25 Aug 2019 11:32:08 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Vlad Buslov <vladbu@...lanox.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 29/38] cls_flower: Convert handle_idr to XArray

On Wed, Aug 21, 2019 at 11:27 AM Vlad Buslov <vladbu@...lanox.com> wrote:
> At first I was confused why you bring up rtnl lock in commit message
> (flower classifier has 'unlocked' flag set and can't rely on it anymore)
> but looking at the code I see that we lost rcu read lock here in commit
> d39d714969cd ("idr: introduce idr_for_each_entry_continue_ul()") and you
> are correctly bringing it back. Adding Cong to advise if it is okay to
> wait for this patch to be accepted or we need to proceed with fixing the
> missing RCU lock as a standalone patch.

Hmm? Isn't ->walk() still called with RTNL lock? tcf_chain_dump()
calls __tcf_get_next_proto() which asserts RTNL.

So why does it still need RCU read lock when having RTNL?