Re: [PATCH net-next] page_pool: add a lockdep check for recycling in hardirq

From: Yunsheng Lin <linyunsheng@huawei.com>
To: Jakub Kicinski <kuba@kernel.org>, <davem@davemloft.net>
Cc: <netdev@vger.kernel.org>, <edumazet@google.com>,
	<pabeni@redhat.com>, <peterz@infradead.org>, <mingo@redhat.com>,
	<will@kernel.org>, <longman@redhat.com>, <boqun.feng@gmail.com>,
	<hawk@kernel.org>, <ilias.apalodimas@linaro.org>
Subject: Re: [PATCH net-next] page_pool: add a lockdep check for recycling in hardirq
Date: Fri, 21 Jul 2023 19:53:30 +0800	[thread overview]
Message-ID: <382d00e5-87af-6a6b-17e2-6640fdd01db5@huawei.com> (raw)
In-Reply-To: <20230720173752.2038136-1-kuba@kernel.org>

On 2023/7/21 1:37, Jakub Kicinski wrote:

...

> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index a3e12a61d456..3ac760fcdc22 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -536,6 +536,8 @@ static void page_pool_return_page(struct page_pool *pool, struct page *page)
>  static bool page_pool_recycle_in_ring(struct page_pool *pool, struct page *page)
>  {
>  	int ret;
> +
> +	lockdep_assert_no_hardirq();

Is there any reason not to put it in page_pool_put_defragged_page() to
catch the case with allow_direct being true when page_pool_recycle_in_ring()
may not be called?

>  	/* BH protection not needed if current is softirq */
>  	if (in_softirq())
>  		ret = ptr_ring_produce(&pool->ring, page);
> @@ -642,6 +644,8 @@ void page_pool_put_page_bulk(struct page_pool *pool, void **data,
>  	int i, bulk_len = 0;
>  	bool in_softirq;
>  
> +	lockdep_assert_no_hardirq();
> +
>  	for (i = 0; i < count; i++) {
>  		struct page *page = virt_to_head_page(data[i]);
>  
> 