linux-kernel - Re: [PATCH RFC v4 1/3] page_pool: fix timing for checking and disabling napi

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Message-ID: <20241204172846.5b360d32@kernel.org>
Date: Wed, 4 Dec 2024 17:28:46 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Yunsheng Lin <linyunsheng@...wei.com>
Cc: <davem@...emloft.net>, <pabeni@...hat.com>, <liuyonglong@...wei.com>,
 <fanghaiqing@...wei.com>, <zhangkun09@...wei.com>, Alexander Lobakin
 <aleksander.lobakin@...el.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>, Ilias Apalodimas
 <ilias.apalodimas@...aro.org>, Eric Dumazet <edumazet@...gle.com>, Simon
 Horman <horms@...nel.org>, <netdev@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v4 1/3] page_pool: fix timing for checking and
 disabling napi_local

On Wed, 4 Dec 2024 19:01:14 +0800 Yunsheng Lin wrote:
> > I don't think this is in the right place.
> > Why not inside page_pool_disable_direct_recycling() ?  
> 
> It is in page_pool_destroy() mostly because:
> 1. Only call synchronize_rcu() when there is inflight pages, which should
>    be an unlikely case, and  synchronize_rcu() might need to be called at
>    least for the case of pool->p.napi not being NULL if it is called inside
>    page_pool_disable_direct_recycling().

Right, my point was that page_pool_disable_direct_recycling() 
is an exported function, its callers also need to be protected.