netdev - Re: [PATCH v3 1/1] wifi: mac80211: fortify the spinlock against deadlock by interrupt

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Message-ID: <20230425153353.GB27649@unreal>
Date:   Tue, 25 Apr 2023 18:33:53 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
Cc:     Johannes Berg <johannes.berg@...el.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Johannes Berg <johannes@...solutions.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Gregory Greenman <gregory.greenman@...el.com>,
        Alexander Wetzel <alexander@...zel-home.de>
Subject: Re: [PATCH v3 1/1] wifi: mac80211: fortify the spinlock against
 deadlock by interrupt

On Tue, Apr 25, 2023 at 11:35:48AM +0200, Mirsad Goran Todorovac wrote:
> In the function ieee80211_tx_dequeue() there is a particular locking
> sequence:
> 
> begin:
> 	spin_lock(&local->queue_stop_reason_lock);
> 	q_stopped = local->queue_stop_reasons[q];
> 	spin_unlock(&local->queue_stop_reason_lock);
> 
> However small the chance (increased by ftracetest), an asynchronous
> interrupt can occur in between of spin_lock() and spin_unlock(),
> and the interrupt routine will attempt to lock the same
> &local->queue_stop_reason_lock again.
> 
> This will cause a costly reset of the CPU and the wifi device or an
> altogether hang in the single CPU and single core scenario.
> 
> This is the probable trace of the deadlock:
> 
> Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel:  Possible unsafe locking scenario:
> Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel:        CPU0
> Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel:        ----
> Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel:   lock(&local->queue_stop_reason_lock);
> Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel:   <Interrupt>
> Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel:     lock(&local->queue_stop_reason_lock);
> Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel:
>                                                  *** DEADLOCK ***

Can you please add to the commit message whole lockdep trace?

And please trim "Apr 10 00:58:33 marvin-IdeaPad-3-15ITL6 kernel: " line prefix,
it doesn't add any value.

Thanks