netdev - RE: [PATCH net-next v4 4/4] net: wangxun: support to use adaptive RX/TX coalescing

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Message-ID: <0bea01dc1175$d1394730$73abd590$@trustnetic.com>
Date: Wed, 20 Aug 2025 09:57:43 +0800
From: Jiawen Wu <jiawenwu@...stnetic.com>
To: "'Jakub Kicinski'" <kuba@...nel.org>
Cc: <netdev@...r.kernel.org>,
	"'Andrew Lunn'" <andrew+netdev@...n.ch>,
	"'David S. Miller'" <davem@...emloft.net>,
	"'Eric Dumazet'" <edumazet@...gle.com>,
	"'Paolo Abeni'" <pabeni@...hat.com>,
	"'Simon Horman'" <horms@...nel.org>,
	"'Jacob Keller'" <jacob.e.keller@...el.com>,
	"'Mengyuan Lou'" <mengyuanlou@...-swift.com>
Subject: RE: [PATCH net-next v4 4/4] net: wangxun: support to use adaptive RX/TX coalescing

On Sat, Aug 16, 2025 2:19 AM, Jakub Kicinski wrote:
> On Tue, 12 Aug 2025 09:50:23 +0800 Jiawen Wu wrote:
> > @@ -878,6 +909,8 @@ static int wx_poll(struct napi_struct *napi, int budget)
> >
> >  	/* all work done, exit the polling mode */
> >  	if (likely(napi_complete_done(napi, work_done))) {
> > +		if (wx->adaptive_itr)
> > +			wx_update_dim_sample(q_vector);
> 
> this is racy, napi is considered released after napi_complete_done()
> returns. So napi_disable() can succeed right after that point...
> 
> > @@ -1611,6 +1708,8 @@ void wx_napi_disable_all(struct wx *wx)
> >  	for (q_idx = 0; q_idx < wx->num_q_vectors; q_idx++) {
> >  		q_vector = wx->q_vector[q_idx];
> >  		napi_disable(&q_vector->napi);
> > +		cancel_work_sync(&q_vector->rx.dim.work);
> > +		cancel_work_sync(&q_vector->tx.dim.work);
> 
> so you may end up with the DIM work scheduled after the device is
> stopped.

But the DIM work doesn't seem to be concerned about the status of napi.
And even if the device is stopped, setting itr would not cause any errors.

I can't fully grasp this point...
Should I move cancel_work_sync() in front of napi_disable()?