netdev - Re: [PATCH 2/3] net: stmmac: Always use the number of configured TX queues

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Date:   Tue, 28 Mar 2017 16:29:15 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Niklas Cassel <niklas.cassel@...s.com>
Cc:     Joao Pinto <Joao.Pinto@...opsys.com>,
        David Miller <davem@...emloft.net>, clabbe.montjoie@...il.com,
        peppe.cavallaro@...com, alexandre.torgue@...com,
        sergei.shtylyov@...entembedded.com, f.fainelli@...il.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH 2/3] net: stmmac: Always use the number of configured TX
 queues

On Tue, Mar 28, 2017 at 04:10:43PM +0200, Niklas Cassel wrote:
> 
> 
> On 03/28/2017 03:57 PM, Thierry Reding wrote:
> > From: Thierry Reding <treding@...dia.com>
> > 
> > Even if hardware supports multiple queues, software can choose to only
> > use a subset of them. Make sure we never try to access uninitialized
> > queues.
> > 
> > Signed-off-by: Thierry Reding <treding@...dia.com>
> > ---
> >  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 106ace3781b3..ec5bba85c529 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -3423,7 +3423,7 @@ static int stmmac_poll(struct napi_struct *napi, int budget)
> >  	struct stmmac_rx_queue *rx_q =
> >  		container_of(napi, struct stmmac_rx_queue, napi);
> >  	struct stmmac_priv *priv = rx_q->priv_data;
> > -	u32 tx_count = priv->dma_cap.number_tx_queues;
> > +	u32 tx_count = priv->plat->tx_queues_to_use;
> >  	u32 chan = rx_q->queue_index;
> >  	u32 work_done = 0;
> >  	u32 queue = 0;
> > 
> 
> Thanks Thierry,
> but this look like an equivalent patch to Joao's
> "net: stmmac: fix number of tx queues in stmmac_poll"
> which I already used during bisecting to avoid random
> crashes in stmmac_tx_clean.

Yeah, patch 3/3 is the important one in this batch. I just sent out the
complete set of 3 because it's what I use on top of linux-next to make
stmmac work again on my setup.

> Have you noticed random RX brokenness after boot in
> recent linux-next tags?

Yes, I was seeing about 8 in 10 bad boots and 2 in 10 good ones.

> It feels like it might trigger more often after a
> cold boot, but that could just be my brain seeing
> patterns that aren't really there :)

It'd be good if you could try applying patch 3/3 since that got me back
to 10/10 successful boots. It's somewhat surprising because I had gone
through the code looking for uninitialized data that would explain why
kcalloc() instead of kmalloc_array() would fix things but didn't find
anything.

Still, that patch works for me, so maybe I was just overlooking
something.

Thierry

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