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From:   Kalle Valo <kvalo@kernel.org>
To:     Sascha Hauer <s.hauer@pengutronix.de>
Cc:     Ping-Ke Shih <pkshih@realtek.com>,
        "linux-wireless\@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        Neo Jou <neojou@gmail.com>,
        Hans Ulli Kroll <linux@ulli-kroll.de>,
        Yan-Hsuan Chuang <tony0620emma@gmail.com>,
        "netdev\@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        "kernel\@pengutronix.de" <kernel@pengutronix.de>,
        Johannes Berg <johannes@sipsolutions.net>,
        Alexander Hochbaum <alex@appudo.com>,
        Da Xue <da@libre.computer>, Bernie Huang <phhuang@realtek.com>,
        Viktor Petrenko <g0000ga@gmail.com>,
        neo_jou <neo_jou@realtek.com>
Subject: Re: [PATCH v3 07/11] rtw88: Add common USB chip support
References: <20221122145226.4065843-1-s.hauer@pengutronix.de>
        <20221122145226.4065843-8-s.hauer@pengutronix.de>
        <1f7aa964766c4f65b836f7e1d716a1e3@realtek.com>
        <20221128103000.GC29728@pengutronix.de>
Date:   Mon, 28 Nov 2022 15:41:32 +0200
In-Reply-To: <20221128103000.GC29728@pengutronix.de> (Sascha Hauer's message
        of "Mon, 28 Nov 2022 11:30:00 +0100")
Message-ID: <87k03f5h83.fsf@kernel.org>
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Sascha Hauer <s.hauer@pengutronix.de> writes:

>> > +static void rtw_usb_write_port_tx_complete(struct urb *urb)
>> > +{
>> > +	struct rtw_usb_txcb *txcb = urb->context;
>> > +	struct rtw_dev *rtwdev = txcb->rtwdev;
>> > +	struct ieee80211_hw *hw = rtwdev->hw;
>> > +
>> > +	while (true) {
>> 
>> Is it possible to have a hard limit to prevent unexpected infinite loop?
>
> Yes, that would be possible, but do you think it's necessary?

It's a common advice to have a limit for loops in kernel.

> Each *txcb is used only once, It's allocated in rtw_usb_tx_agg_skb() and
> &txcb->tx_ack_queue is filled with a limited number of skbs there. These
> skbs is then iterated over in rtw_usb_write_port_tx_complete(), so I don't
> see a way how we could end up in an infinite loop here.

Everyone always say that their code is bugfree ;) More seriously though,
even if it would be bugfree now someone else can add buggy code later.
So much better to have a limit for the loop.

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