netdev - Re: [PATCH RFC net-next/mm V1 1/3] page_pool: Remove workqueue in new shutdown scheme

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Message-ID: <48661b51-1cbb-e3e0-a909-6d0a1532733a@huawei.com>
Date:   Thu, 27 Apr 2023 08:57:58 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        <netdev@...r.kernel.org>, Eric Dumazet <eric.dumazet@...il.com>,
        <linux-mm@...ck.org>, Mel Gorman <mgorman@...hsingularity.net>
CC:     <lorenzo@...nel.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        <bpf@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <willy@...radead.org>
Subject: Re: [PATCH RFC net-next/mm V1 1/3] page_pool: Remove workqueue in new
 shutdown scheme

On 2023/4/26 1:15, Jesper Dangaard Brouer wrote:
> @@ -609,6 +609,8 @@ void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
>  		recycle_stat_inc(pool, ring_full);
>  		page_pool_return_page(pool, page);
>  	}
> +	if (pool->p.flags & PP_FLAG_SHUTDOWN)
> +		page_pool_shutdown_attempt(pool);

It seems we have allowed page_pool_shutdown_attempt() to be called
concurrently here, isn't there a time window between atomic_inc_return_relaxed()
and page_pool_inflight() for pool->pages_state_release_cnt, which may cause
double calling of page_pool_free()?