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

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Date: Tue, 23 May 2023 10:13:14 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Ilias Apalodimas <ilias.apalodimas@...aro.org>, Jesper Dangaard Brouer
	<jbrouer@...hat.com>
CC: <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<brouer@...hat.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Jesper Dangaard Brouer <hawk@...nel.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 2023/5/22 19:45, Ilias Apalodimas wrote:
>> 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! :-)

It was spotted when implementing the below patch:)

https://patchwork.kernel.org/project/netdevbpf/patch/168269857929.2191653.13267688321246766547.stgit@firesoul/#25325801

Do you still working on optimizing the page_pool destroy
process? If not, do you mind if I carry it on based on
that?