Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Kalle Valo <kvalo@kernel.org>
To:     <Ajay.Kathat@microchip.com>
Cc:     <linux-wireless@vger.kernel.org>, <Claudiu.Beznea@microchip.com>,
        <Sripad.Balwadgi@microchip.com>, <mwalle@kernel.org>
Subject: Re: [PATCH] wifi: wilc1000: fix kernel oops during interface down during background scan
References: <20230404012010.15261-1-ajay.kathat@microchip.com>
        <87wn1mok5g.fsf@kernel.org>
        <cffca4d1-5ab5-0633-7bab-00d65526bfa7@microchip.com>
Date:   Sat, 06 May 2023 08:50:58 +0300
In-Reply-To: <cffca4d1-5ab5-0633-7bab-00d65526bfa7@microchip.com> (Ajay
        Kathat's message of "Fri, 5 May 2023 20:53:12 +0000")
Message-ID: <87sfcanh31.fsf@kernel.org>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

<Ajay.Kathat@microchip.com> writes:

>>> @@ -781,13 +776,15 @@ static int wilc_mac_close(struct net_device *ndev)
>>>       if (vif->ndev) {
>>>               netif_stop_queue(vif->ndev);
>>>
>>> +             if (wl->open_ifcs == 0)
>>> +                     wl->close = 1;
>>> +
>> 
>> wl-close is an int, I wonder if it's racy to int as a flag like this? In
>> cases like this I usually use set_bit() & co because those guarantee
>> atomicity, though don't know if that's overkill.
>> 
>
> I think it's a good idea to use an atomic operation but I am not sure if
> using atomic for 'wl->close' will have much impact. For instance, if any
> new work gets added to the workqueue before the 'wl->close=1' is fully
> completed, then that work would get executed as normal.

Sure, this is most likely a small race condition. But still a race.

> However, I feel it's safe to define 'wl->close' as atomic_t type. I will
> prepare the conversion patch and will try to include it along with the
> updated version of this patch.

Why atomic_t? You only use values 0 and 1 so test_bit() and set_bit()
sounds more approriate to me.


-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches