Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 25 Apr 2023 18:33:53 +0300
From:   Leon Romanovsky <leon@kernel.org>
To:     Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Cc:     Johannes Berg <johannes.berg@intel.com>,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Johannes Berg <johannes@sipsolutions.net>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Gregory Greenman <gregory.greenman@intel.com>,
        Alexander Wetzel <alexander@wetzel-home.de>
Subject: Re: [PATCH v3 1/1] wifi: mac80211: fortify the spinlock against
 deadlock by interrupt
Message-ID: <20230425153353.GB27649@unreal>
References: <20230425093547.1131-1-mirsad.todorovac@alu.unizg.hr>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230425093547.1131-1-mirsad.todorovac@alu.unizg.hr>
Precedence: bulk

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