netdev - Re: [PATCH 1/5] net: remove bogus RCU annotations on socket.wq

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Message-Id: <20180730.090929.307167658012418290.davem@davemloft.net>
Date:   Mon, 30 Jul 2018 09:09:29 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     hch@....de
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH 1/5] net: remove bogus RCU annotations on socket.wq

From: Christoph Hellwig <hch@....de>
Date: Mon, 30 Jul 2018 09:44:54 +0200

> On Sun, Jul 29, 2018 at 01:05:51PM -0700, David Miller wrote:
>> From: Christoph Hellwig <hch@....de>
>> Date: Fri, 27 Jul 2018 16:02:10 +0200
>> 
>> > We never use RCU protection for it, just a lot of cargo-cult
>> > rcu_deference_protects calls.
>> > 
>> > Note that we do keep the kfree_rcu call for it, as the references through
>> > struct sock are RCU protected and thus might require a grace period before
>> > freeing.
>> > 
>> > Signed-off-by: Christoph Hellwig <hch@....de>
>> 
>> These were added by Eric Dumazet and I would never accuse him of cargo
>> cult programming.
>> 
>> All of the rcu_dereference_protects() calls are legit, even though some
>> of them use '1' as the protects condition because in fact we know the
>> object is dead and gone through an RCU cycle at that point.
> 
> I disagree, but I'll resend it the patch with Eric and Paul in CC to
> settle the argument.

Thank you.