linux-kernel - Re: [PATCH] skbuff: fix a data race in skb_queue

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Message-Id: <D743FB35-3736-45E9-9DE1-8E81929D67C1@lca.pw>
Date:   Mon, 3 Feb 2020 15:19:13 -0500
From:   Qian Cai <cai@....pw>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, elver@...gle.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] skbuff: fix a data race in skb_queue_len()



> On Feb 3, 2020, at 2:42 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
> We do not want to add READ_ONCE() for all uses of skb_queue_len()
> 
> This could hide some real bugs, and could generate slightly less
> efficient code in the cases we have the lock held.

Good point. I should have thought about that. How about introducing 2 new helpers.

skb_queue_len_once()
unix_recvq_full_once()

which will have a READ_ONCE() there, and then unix_dgram_sendmsg() could use that instead?