linux-kernel - Re: [PATCH 2/2] net: ethernet: stmmac: remove private tx queue lock

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Message-Id: <20161208.102641.2159772626439340664.davem@davemloft.net>
Date:   Thu, 08 Dec 2016 10:26:41 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     pavel@....cz
Cc:     LinoSanfilippo@....de, bh74.an@...sung.com, ks.giri@...sung.com,
        vipul.pandya@...sung.com, peppe.cavallaro@...com,
        alexandre.torgue@...com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] net: ethernet: stmmac: remove private tx queue lock

From: Pavel Machek <pavel@....cz>
Date: Thu, 8 Dec 2016 15:08:46 +0100

> On Wed 2016-12-07 18:41:11, David Miller wrote:
>> From: Pavel Machek <pavel@....cz>
>> Date: Wed, 7 Dec 2016 22:37:57 +0100
>> 
>> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> > index 982c952..7415bc2 100644
>> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> > @@ -1308,7 +1308,7 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
>> >  	unsigned int bytes_compl = 0, pkts_compl = 0;
>> >  	unsigned int entry = priv->dirty_tx;
>> >  
>> > -	spin_lock(&priv->tx_lock);
>> > +	netif_tx_lock_bh(priv->dev);
>> >  
>> >  	priv->xstats.tx_clean++;
>> >  
>> 
>> stmmac_tx_clean() runs from either the timer or the NAPI poll handler,
>> both execute from software interrupts, therefore _bh() should be
>> unnecessary.
> 
> I've tried the test again with netif_tx_lock() (not _bh()) and it
> survived for more then four hours. Strange...

It's not strange, it's completely expected.