From: bot+bpf-ci@kernel.org
To: ameryhung@gmail.com,bpf@vger.kernel.org
Cc: netdev@vger.kernel.org,alexei.starovoitov@gmail.com,andrii@kernel.org,daniel@iogearbox.net,eddyz87@gmail.com,memxor@gmail.com,martin.lau@kernel.org,shakeel.butt@linux.dev,roman.gushchin@linux.dev,kuniyu@google.com,kerneljasonxing@gmail.com,ameryhung@gmail.com,kernel-team@meta.com,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,mason@kernel.org,ihor.solodrai@linux.dev
Subject: Re: [PATCH bpf-next v4 02/15] bpf: Make struct_ops tasks_rcu grace period optional
Date: Thu, 17 Sep 2026 21:34:08 +0000 (UTC) [thread overview]
Message-ID: <ec00a1c9972f8bf493c2bb4b9d817d88169eaf23a870bc087a50ad110a11b469@mail.kernel.org> (raw)
In-Reply-To: <20260917200542.3689605-3-ameryhung@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 1806 bytes --]
> diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
> index 791e15063237c..e224ecafbd699 100644
> --- a/net/ipv4/bpf_tcp_ca.c
> +++ b/net/ipv4/bpf_tcp_ca.c
> @@ -339,6 +339,22 @@ static struct bpf_struct_ops bpf_tcp_congestion_ops = {
> .validate = bpf_tcp_ca_validate,
> .name = "tcp_congestion_ops",
> .cfi_stubs = &__bpf_ops_tcp_congestion_ops,
> + /* The struct_ops's function may switch to another struct_ops.
> + *
> + * For example, bpf_tcp_cc_x->init() may switch to
> + * another tcp_cc_y by calling
> + * setsockopt(TCP_CONGESTION, "tcp_cc_y").
> + * During the switch, bpf_struct_ops_put(tcp_cc_x) is called
> + * and its refcount may reach 0 which then free its
> + * trampoline image while tcp_cc_x is still running.
> + *
> + * A vanilla rcu gp is to wait for all bpf-tcp-cc prog
> + * to finish. bpf-tcp-cc prog is non sleepable.
> + * A rcu_tasks gp is to wait for the last few insn
> + * in the tramopline image to finish before releasing
> + * the trampoline image.
> + */
> + .free_after_tasks_rcu_gp = true,
> .owner = THIS_MODULE,
> };
This isn't a bug, but now that this comment lives next to
.free_after_tasks_rcu_gp rather than next to the synchronize_rcu_mult()
call, would it help to say where the vanilla rcu gp it mentions actually
comes from? The comment talks about both grace periods, but in this new
location it only annotates the tasks RCU flag. A reader might wonder
where bpf_tcp_congestion_ops gets its vanilla grace period (it comes
from bpf_map_put()'s call_rcu() via map->free_after_rcu_gp).
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/35271288839
next prev parent reply other threads:[~2026-09-17 21:34 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 20:05 [PATCH bpf-next v4 00/15] bpf: A common way to attach struct_ops to a cgroup Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 01/15] bpf: Remove __rcu tagging in st_link->map Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 02/15] bpf: Make struct_ops tasks_rcu grace period optional Amery Hung
2026-09-17 21:34 ` bot+bpf-ci [this message]
2026-09-17 20:05 ` [PATCH bpf-next v4 03/15] bpf: Add bpf_struct_ops accessor helpers Amery Hung
2026-09-17 21:16 ` bot+bpf-ci
2026-09-17 20:05 ` [PATCH bpf-next v4 04/15] bpf: Remove unnecessary prog_list_prog() check Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 05/15] bpf: Replace prog_list_prog() check with direct pl->prog and pl->link check Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 06/15] bpf: Add prog_list_init_item(), prog_list_replace_item(), and prog_list_id() Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 07/15] bpf: Move LSM trampoline unlink into bpf_cgroup_link_auto_detach() Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 08/15] bpf: Add a few bpf_cgroup_array_* helper functions Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 09/15] bpf: Add infrastructure to support attaching struct_ops to cgroups Amery Hung
2026-09-17 21:34 ` bot+bpf-ci
2026-09-17 20:05 ` [PATCH bpf-next v4 10/15] bpf: Allow all struct_ops to use bpf_dynptr_from_skb() Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 11/15] bpf: tcp: Support selected sock_ops callbacks as struct_ops Amery Hung
2026-09-17 21:34 ` bot+bpf-ci
2026-09-17 20:05 ` [PATCH bpf-next v4 12/15] bpf: tcp: Support parse/len/write header option hooks in bpf_tcp_ops Amery Hung
2026-09-17 21:34 ` bot+bpf-ci
2026-09-17 20:05 ` [PATCH bpf-next v4 13/15] libbpf: Support attaching struct_ops to a cgroup Amery Hung
2026-09-17 20:05 ` [PATCH bpf-next v4 14/15] selftests/bpf: Test " Amery Hung
2026-09-17 21:34 ` bot+bpf-ci
2026-09-17 20:05 ` [PATCH bpf-next v4 15/15] selftests/bpf: Add test for bpf_tcp_ops header option hooks Amery Hung
2026-09-19 5:40 ` [PATCH bpf-next v4 00/15] bpf: A common way to attach struct_ops to a cgroup patchwork-bot+netdevbpf
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