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Subject: Re: [PATCH bpf-next v7 2/8] net: Update an existing TCP congestion
 control algorithm.
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To:     Daniel Borkmann <daniel@iogearbox.net>
Cc:     netdev@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
        Kui-Feng Lee <kuifeng@meta.com>, bpf@vger.kernel.org,
        ast@kernel.org, song@kernel.org, kernel-team@meta.com,
        andrii@kernel.org, sdf@google.com
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From:   Martin KaFai Lau <martin.lau@linux.dev>
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On 3/17/23 8:23 AM, Daniel Borkmann wrote:
>  From the function itself what is not clear whether
> callers that replace an existing one should do the synchronize_rcu() themselves 
> or if this should
> be part of tcp_update_congestion_control?

bpf_struct_ops_map_free (in patch 1) also does synchronize_rcu() for another 
reason (bpf_setsockopt), so the caller (bpf_struct_ops) is doing it. From 
looking at tcp_unregister_congestion_control(), make sense that it is more 
correct to have another synchronize_rcu() also in tcp_update_congestion_control 
in case there will be other non bpf_struct_ops caller doing update in the future.