netdev - Re: [PATCH net-next] net: ethernet: mtk_wed: fix possible deadlock if mtk_wed_wo

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Message-ID: <20221205174441.30741550@kernel.org>
Date:   Mon, 5 Dec 2022 17:44:41 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     Leon Romanovsky <leon@...nel.org>, netdev@...r.kernel.org,
        nbd@....name, john@...ozen.org, sean.wang@...iatek.com,
        Mark-MC.Lee@...iatek.com, davem@...emloft.net, edumazet@...gle.com,
        pabeni@...hat.com, matthias.bgg@...il.com,
        linux-mediatek@...ts.infradead.org, lorenzo.bianconi@...hat.com
Subject: Re: [PATCH net-next] net: ethernet: mtk_wed: fix possible deadlock
 if mtk_wed_wo_init fails

On Mon, 5 Dec 2022 10:04:07 +0100 Lorenzo Bianconi wrote:
> > IMHO, it is a culprit, proper error unwind means that you won't call to
> > uninit functions for something that is not initialized yet. It is better
> > to fix it instead of adding "if (!wo) ..." checks.  
> 
> So, iiuc, you would prefer to do something like:
> 
> __mtk_wed_detach()
> {
> 	...
> 	if (mtk_wed_get_rx_capa(dev) && wo) {
> 		mtk_wed_wo_reset(dev);
> 		mtk_wed_free_rx_rings(dev);
> 		mtk_wed_wo_deinit(hw);
> 	}
> 	...
> 	
> Right? I am fine both ways :)

FWIW, that does seem slightly better to me as well.
Also - aren't you really fixing multiple issues here 
(even if on the same error path)? The locking, 
the null-checking and the change in mtk_wed_wo_reset()?