linux-kernel - Re: [PATCH] net/sched: use spin_lock_bh() on &gact->tcf

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Message-ID: <20231004170120.1c80b3b4@kernel.org>
Date:   Wed, 4 Oct 2023 17:01:20 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Chengfeng Ye <dg573847474@...il.com>
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/sched: use spin_lock_bh() on &gact->tcf_lock

On Tue, 26 Sep 2023 18:26:25 +0000 Chengfeng Ye wrote:
> I find tcf_gate_act() acquires &gact->tcf_lock without disable
> bh explicitly, as gact->tcf_lock is acquired inside timer under
> softirq context, if tcf_gate_act() is not called with bh disable
> by default or under softirq context(which I am not sure as I cannot
> find corresponding documentation), then it could be the following 
> deadlocks.
> 
> tcf_gate_act()
> --> spin_loc(&gact->tcf_lock)  
> <interrupt>
>    --> gate_timer_func()
>    --> spin_lock(&gact->tcf_lock)  

This is a TC action, I don't think it can run without BH being already
disabled, can it?
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