netdev - Re: [igb] netconsole triggers warning in netpoll_poll

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Date:   Mon, 26 Apr 2021 08:47:36 +0200
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Alexander Duyck <alexander.duyck@...il.com>,
        linux-kernel@...r.kernel.org,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: Re: [igb] netconsole triggers warning in netpoll_poll_dev

Hello.

On Fri, Apr 23, 2021 at 03:58:36PM -0700, Jakub Kicinski wrote:
> On Fri, 23 Apr 2021 10:19:44 +0200 Oleksandr Natalenko wrote:
> > On Wed, Apr 07, 2021 at 04:06:29PM -0700, Alexander Duyck wrote:
> > > On Wed, Apr 7, 2021 at 11:07 AM Jakub Kicinski <kuba@...nel.org> wrote:  
> > > > Sure, that's simplest. I wasn't sure something is supposed to prevent
> > > > this condition or if it's okay to cover it up.  
> > > 
> > > I'm pretty sure it is okay to cover it up. In this case the "budget -
> > > 1" is supposed to be the upper limit on what can be reported. I think
> > > it was assuming an unsigned value anyway.
> > > 
> > > Another alternative would be to default clean_complete to !!budget.
> > > Then if budget is 0 clean_complete would always return false.  
> > 
> > So, among all the variants, which one to try? Or there was a separate
> > patch sent to address this?
> 
> Alex's suggestion is probably best.
> 
> I'm not aware of the fix being posted. Perhaps you could take over and
> post the patch if Intel doesn't chime in?

So, IIUC, Alex suggests this:

```
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index a45cd2b416c8..7503d5bf168a 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -7981,7 +7981,7 @@ static int igb_poll(struct napi_struct *napi, int budget)
 						     struct igb_q_vector,
 						     napi);
 	bool clean_complete = true;
-	int work_done = 0;
+	unsigned int work_done = 0;
 
 #ifdef CONFIG_IGB_DCA
 	if (q_vector->adapter->flags & IGB_FLAG_DCA_ENABLED)
@@ -8008,7 +8008,7 @@ static int igb_poll(struct napi_struct *napi, int budget)
 	if (likely(napi_complete_done(napi, work_done)))
 		igb_ring_irq_enable(q_vector);
 
-	return min(work_done, budget - 1);
+	return min_t(unsigned int, work_done, budget - 1);
 }
 
 /**
```

Am I right?

Thanks.

-- 
  Oleksandr Natalenko (post-factum)