netdev - Re: [bug report] net/sched: sch_qfq: Fix race condition on qfq

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Message-ID: <c25f3831-dee3-4eee-86ed-8eb6e58a3dad@suswa.mountain>
Date: Thu, 17 Jul 2025 23:44:56 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Xiang Mei <xmei5@....edu>
Cc: netdev@...r.kernel.org
Subject: Re: [bug report] net/sched: sch_qfq: Fix race condition on
 qfq_aggregate

On Thu, Jul 17, 2025 at 01:06:15PM -0700, Xiang Mei wrote:
> Thanks Dan for the explanations. 
> 
> What do you think about this solution: We split qfq_destory_class to two 
> parts: qfq_rm_from_agg(q, cl) and the left calls. Since the race condition
> is about agg, we can keep the left calls out of the lock but moving 
> qfq_rm_from_agg into the lock.
> 
> This could avoid calling __qdisc_destroy in the lock. Please let me know 
> if it works, I can help to deliever a new version of patch.

What you're saying sounds reasonable to me, but I don't know this code
at all so my opinions on this are a bit worthless.

The patch was already merged into the net tree so you can't send a new
version.  It has a be a fixup patch based on top of the current tree
with a Fixes tag etc.

regards,
dan carpenter