netdev - Re: [PATCH net-next v2 04/12] net-timestamp: add static key to control the whole bpf extension

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Message-ID: <49a87125-d5bd-4b8d-964e-0d745e9e669b@linux.dev>
Date: Tue, 15 Oct 2024 23:31:07 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, dsahern@...nel.org, willemdebruijn.kernel@...il.com,
 willemb@...gle.com, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
 eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev,
 john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me,
 haoluo@...gle.com, jolsa@...nel.org, bpf@...r.kernel.org,
 netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v2 04/12] net-timestamp: add static key to
 control the whole bpf extension

On 10/15/24 6:04 PM, Jason Xing wrote:
> To be honest, I considered how to disable the static key. Like you
> said, I failed to find a good chance that I can accurately disable it.

It at least needs to be disabled whenever that bpf prog got detached.

> 
>> The bpf prog may be detached also. (IF) it ends up staying with the
>> cgroup/sockops interface, it should depend on the existing static key in
>> cgroup_bpf_enabled(CGROUP_SOCK_OPS) instead of adding another one.

> Are you suggesting that we need to remove the current static key? In
> the previous thread, the reason why Willem came up with this idea is,
> I think, to avoid affect the non-bpf timestamping feature.

Take a look at cgroup_bpf_enabled(CGROUP_SOCK_OPS). There is a static key. I am 
saying to use that existing key. afaict, the newly added bpf_tstamp_control key 
is mainly an optimization. Yes, cgroup_bpf_enabled(CGROUP_SOCK_OPS) is less 
granular but it has the needed accounting to disable whenever the bpf prog got 
detached, so better just reuse the cgroup_bpf_enabled(CGROUP_SOCK_OPS).