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From: Yan Zhai <yan@cloudflare.com>
Date: Tue, 27 Feb 2024 15:17:54 -0600
Message-ID: <CAO3-Pbpy7V+ZesnG7vTmV4msHW3M-sMa2Pfim2yU8jL=hbYq3A@mail.gmail.com>
Subject: Re: [PATCH] net: raise RCU qs after each threaded NAPI poll
To: Eric Dumazet <edumazet@google.com>
Cc: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>, 
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>, Jiri Pirko <jiri@resnulli.us>, 
	Simon Horman <horms@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, 
	Lorenzo Bianconi <lorenzo@kernel.org>, Coco Li <lixiaoyan@google.com>, Wei Wang <weiwan@google.com>, 
	Alexander Duyck <alexanderduyck@fb.com>, Hannes Frederic Sowa <hannes@stressinduktion.org>, 
	linux-kernel@vger.kernel.org, rcu@vger.kernel.org, bpf@vger.kernel.org, 
	kernel-team@cloudflare.com
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On Tue, Feb 27, 2024 at 10:44=E2=80=AFAM Eric Dumazet <edumazet@google.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.