netdev - RE: Report on abnormal behavior of "page

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Date: Thu, 1 Feb 2024 02:37:02 +0000
From: Justin Lai <justinlai0215@...ltek.com>
To: Yunsheng Lin <linyunsheng@...wei.com>,
        "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
Subject: RE: Report on abnormal behavior of "page_pool" API

> On 2024/1/31 15:31, Justin Lai wrote:
> > To whom it may concern,
> >
> > I hope this email finds you well. I am writing to report a behavior
> > which seems to be abnormal.
> >
> > When I remove the module, I call page_pool_destroy() to release the
> 
> Which module?
The PCIe driver
> 
> > page_pool, but this message appears, page_pool_release_retry() stalled
> > pool shutdown 1024 inflight 120 sec. Then I tried to return the page
> > to page_pool before calling page_pool_destroy(), so I called
> > page_pool_put_full_page() first, but after doing so, this message was
> > printed, page_pool_empty_ring() page_pool refcnt 0 violation, and the
> 
> As we have "page_ref_count(page) == 1" checking to allow recycling page in
> pool->ring:
> https://elixir.bootlin.com/linux/v6.8-rc2/source/net/core/page_pool.c#L654
> 
> It seems somebody is still using the page and manipulating _refcount while the
> page is sitting in the pool->ring?

I will confirm this part again, thank you for your reply.
> 
> 
> > computer crashed.
> >
> > I would like to ask what could be causing this and how I should fix it.
> 
> Not sure if you read the below doc for page_pool, understanding the internal
> detail and the API usages may help you debuging the problem:
> Documentation/networking/page_pool.rst

Thank you for your reply. I have read this document, but I will study it again.
> 
> >
> > The information on my working environment is: Ubuntu23.10, linux
> > kernel 6.4, 6.5, 6.6
> >
> > Thank you for your time and efforts, I am looking forward to your reply.
> >
> > Best regards,
> > Justin
> >
> > .
> >