netdev - Re: [PATCH net-next 2/3] net: ethernet: mtk_eth

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Date:   Tue, 20 Apr 2021 16:58:16 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Frank Wunderlich <frank-w@...lic-files.de>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        john@...ozen.org, nbd@....name, sean.wang@...iatek.com,
        Mark-MC.Lee@...iatek.com, dqfext@...il.com
Subject: Re: [PATCH net-next 2/3] net: ethernet: mtk_eth_soc: missing mutex

On Tue, Apr 20, 2021 at 01:51:07PM +0200, Frank Wunderlich wrote:
> Am 18. April 2021 23:11:44 MESZ schrieb Pablo Neira Ayuso <pablo@...filter.org>:
> >Patch 2ed37183abb7 ("netfilter: flowtable: separate replace, destroy
> >and
> >stats to different workqueues") splits the workqueue per event type.
> >Add
> >a mutex to serialize updates.
> >
> >Fixes: 502e84e2382d ("net: ethernet: mtk_eth_soc: add flow offloading
> >support")
> >Reported-by: Frank Wunderlich <frank-w@...lic-files.de>
> >Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
> 
> Hi Pablo,
> 
> As far we tested it, the mutex does not avoid the hang. It looks a bit better,but at the end it was fixed by this Patch
> 
> https://patchwork.kernel.org/project/linux-mediatek/patch/20210417072905.207032-1-dqfext@gmail.com/
> 
> Alex did some tests without the lock here and it still looks stable.
> So it looks like it is not needed

It might be hard to trigger the race, but it's needed. There are
several workqueues racing to add and delete entries from the driver
flowtable representation which has no locks.