netdev - Re: [PATCH -next v2 0/3] staging: rtl8192e: Do not call kfree_skb() under spin_lock

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Message-ID: <d7326392-56e4-4ccb-a878-0a03c91d0d85@kadam.mountain>
Date: Tue, 5 Sep 2023 14:59:47 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Jinjie Ruan <ruanjinjie@...wei.com>, netdev@...r.kernel.org
Cc: gregkh@...uxfoundation.org, philipp.g.hortmann@...il.com,
	straube.linux@...il.com, Larry.Finger@...inger.net,
	wlanfae@...ltek.com, mikem@...g3k.org, seanm@...nm.ca,
	linux-staging@...ts.linux.dev
Subject: Re: [PATCH -next v2 0/3] staging: rtl8192e: Do not call kfree_skb()
 under spin_lock_irqsave()

Added netdev because they're really the experts.

On Fri, Aug 25, 2023 at 09:52:10AM +0800, Jinjie Ruan wrote:
> It is not allowed to call kfree_skb() from hardware interrupt
> context or with interrupts being disabled.

There are no comments which say that this is not allowed.  I have
reviewed the code to see why it's not allowed.  The only thing I can
see is that maybe the skb->destructor(skb); in skb_release_head_state()
sleeps?  Or possibly the uarg->callback() in skb_zcopy_clear()?

Can you comment more on why this isn't allowed?  Was this detected at
runtime?  Do you have a stack trace?

Once I know more I can add this to Smatch so that it is detected
automatically using static analysis.

regards,
dan carpenter