netdev - RE: [PATCH net v2] igb: fix netpoll exit with traffic

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Message-ID: <DM6PR12MB451635351CFBBD86059A0078D8619@DM6PR12MB4516.namprd12.prod.outlook.com>
Date:   Wed, 24 Nov 2021 07:51:41 +0000
From:   Danielle Ratson <danieller@...dia.com>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Alexander Duyck <alexander.duyck@...il.com>
Subject: RE: [PATCH net v2] igb: fix netpoll exit with traffic


> -----Original Message-----
> From: Jesse Brandeburg <jesse.brandeburg@...el.com>
> Sent: Tuesday, November 23, 2021 10:40 PM
> To: intel-wired-lan@...ts.osuosl.org
> Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>;
> netdev@...r.kernel.org; Oleksandr Natalenko
> <oleksandr@...alenko.name>; Danielle Ratson <danieller@...dia.com>;
> Alexander Duyck <alexander.duyck@...il.com>
> Subject: [PATCH net v2] igb: fix netpoll exit with traffic
> 
> Oleksandr brought a bug report where netpoll causes trace messages in the
> log on igb.
> 
> Danielle brought this back up as still occuring, so we'll try again.

Hi Jessi,

Ill run tests with you patch and give you results for if it is ok.
Thanks!

> 
> [22038.710800] ------------[ cut here ]------------ [22038.710801]
> igb_poll+0x0/0x1440 [igb] exceeded budget in poll [22038.710802]
> WARNING: CPU: 12 PID: 40362 at net/core/netpoll.c:155
> netpoll_poll_dev+0x18a/0x1a0
> 
> As Alex suggested, change the driver to return work_done at the exit of
> napi_poll, which should be safe to do in this driver because it is not polling
> multiple queues in this single napi context (multiple queues attached to one
> MSI-X vector). Several other drivers contain the same simple sequence, so I
> hope this will not create new problems.
> 
> Fixes: 16eb8815c235 ("igb: Refactor clean_rx_irq to reduce overhead and
> improve performance")
> Reported-by: Oleksandr Natalenko <oleksandr@...alenko.name>
> Reported-by: Danielle Ratson <danieller@...dia.com>
> Suggested-by: Alexander Duyck <alexander.duyck@...il.com>
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
> ---
> COMPILE TESTED ONLY! I have no way to reproduce this even on a machine I
> have with igb. It works fine to load the igb driver and netconsole with no
> errors.
> ---
> v2: simplified patch with an attempt to make it work
> v1: original patch that apparently didn't work
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> b/drivers/net/ethernet/intel/igb/igb_main.c
> index e647cc89c239..5e24b7ce5a92 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -8104,7 +8104,7 @@ 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 work_done;
>  }
> 
>  /**
> --
> 2.33.1