netdev - Re: [PATCH net] nfp: do not send control messages during cleanup

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Date:   Tue, 15 Dec 2020 11:22:51 +0100
From:   Simon Horman <simon.horman@...ronome.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     David Miller <davem@...emloft.net>,
        Louis Peens <louis.peens@...ronome.com>,
        netdev@...r.kernel.org, oss-drivers@...ronome.com,
        wenxu <wenxu@...oud.cn>
Subject: Re: [PATCH net] nfp: do not send control messages during cleanup

On Mon, Dec 14, 2020 at 06:26:50PM -0800, Jakub Kicinski wrote:
> On Fri, 11 Dec 2020 10:27:38 +0100 Simon Horman wrote:
> > On cleanup the txbufs are freed before app cleanup. But app clean-up may
> > result in control messages due to use of common control paths. There is no
> > need to clean-up the NIC in such cases so simply discard requests. Without
> > such a check a NULL pointer dereference occurs.
> > 
> > Fixes: a1db217861f3 ("net: flow_offload: fix flow_indr_dev_unregister path")
> > Cc: wenxu <wenxu@...oud.cn>
> > Signed-off-by: Simon Horman <simon.horman@...ronome.com>
> > Signed-off-by: Louis Peens <louis.peens@...ronome.com>
> 
> Hm. We can apply this as a quick fix, but I'd think that app->stop
> (IIRC that's the callback) is responsible for making sure that
> everything gets shut down and no more cmsgs can be generated after
> ctrl vNIC goes down. Perhaps some code needs to be reshuffled between
> init/clean and start/stop for flower? WDYT?

Thanks Jakub,

I was a bit concerned with fragility in the clean-up path, which is why I
had opted for this simple solution. However, looking at your suggestion
above it seems simple to move the cleanup to app->stop. I'll work on
posting a patch to implement your suggestion.