linux-kernel - Re: [PATCH net] page_pool: fix inconsistency for page_pool_ring

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Message-ID: <1fc46094-a72a-f7e4-ef18-15edb0d56233@redhat.com>
Date:   Mon, 22 May 2023 13:08:20 +0200
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Yunsheng Lin <linyunsheng@...wei.com>, davem@...emloft.net,
        kuba@...nel.org, pabeni@...hat.com
Cc:     brouer@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH net] page_pool: fix inconsistency for
 page_pool_ring_[un]lock()



On 22/05/2023 05.17, Yunsheng Lin wrote:
> page_pool_ring_[un]lock() use in_softirq() to decide which
> spin lock variant to use, and when they are called in the
> context with in_softirq() being false, spin_lock_bh() is
> called in page_pool_ring_lock() while spin_unlock() is
> called in page_pool_ring_unlock(), because spin_lock_bh()
> has disabled the softirq in page_pool_ring_lock(), which
> causes inconsistency for spin lock pair calling.
> 
> This patch fixes it by returning in_softirq state from
> page_pool_producer_lock(), and use it to decide which
> spin lock variant to use in page_pool_producer_unlock().
> 
> As pool->ring has both producer and consumer lock, so
> rename it to page_pool_producer_[un]lock() to reflect
> the actual usage. Also move them to page_pool.c as they
> are only used there, and remove the 'inline' as the
> compiler may have better idea to do inlining or not.
> 
> Fixes: 7886244736a4 ("net: page_pool: Add bulk support for ptr_ring")
> Signed-off-by: Yunsheng Lin<linyunsheng@...wei.com>

Thanks for spotting and fixing this! :-)

Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>