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

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Date:   Wed, 7 Dec 2022 00:52:28 +0100
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     Jakub Kicinski <kuba@...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

> > > 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()?

wo NULL pointer issue was not hit before for the deadlock one (so I fixed them
in the same patch).
Do you prefer to split them in two patches? (wo null pointer fix first).

I have posted v2 addressing Leon's comments but I need to post a v3 to add
missing WARN_ON.

Regards,
Lorenzo

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