linux-kernel - Re: [PATCH] net: raise RCU qs after each threaded NAPI poll

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Message-ID: <CAO3-Pbpy7V+ZesnG7vTmV4msHW3M-sMa2Pfim2yU8jL=hbYq3A@mail.gmail.com>
Date: Tue, 27 Feb 2024 15:17:54 -0600
From: Yan Zhai <yan@...udflare.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Jiri Pirko <jiri@...nulli.us>, 
	Simon Horman <horms@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Lorenzo Bianconi <lorenzo@...nel.org>, Coco Li <lixiaoyan@...gle.com>, Wei Wang <weiwan@...gle.com>, 
	Alexander Duyck <alexanderduyck@...com>, Hannes Frederic Sowa <hannes@...essinduktion.org>, 
	linux-kernel@...r.kernel.org, rcu@...r.kernel.org, bpf@...r.kernel.org, 
	kernel-team@...udflare.com
Subject: Re: [PATCH] net: raise RCU qs after each threaded NAPI poll

On Tue, Feb 27, 2024 at 10:44 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> Hmm....
> Why napi_busy_loop() does not have a similar problem ?
>
That's a good question. Let me try if I can repro this on a busy loop
as well, since the structure seems very alike.

> It is unclear why rcu_all_qs() in __cond_resched() is guarded by
>
> #ifndef CONFIG_PREEMPT_RCU
>      rcu_all_qs();
> #endif
>
>
> Thanks.