Re: [net-next PATCH RFC 2/5] net: ethernet: stmicro: stmmac: first disable all queues in release

From: Christian Marangi <ansuelsmth@gmail.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <joabreu@synopsys.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Paolo Abeni <pabeni@redhat.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	netdev@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [net-next PATCH RFC 2/5] net: ethernet: stmicro: stmmac: first disable all queues in release
Date: Wed, 29 Jun 2022 12:44:53 +0200	[thread overview]
Message-ID: <62bc2d26.1c69fb81.8efff.df8d@mx.google.com> (raw)
In-Reply-To: <20220628205435.44b0c78c@kernel.org>

On Tue, Jun 28, 2022 at 08:54:35PM -0700, Jakub Kicinski wrote:
> On Tue, 28 Jun 2022 03:33:39 +0200 Christian Marangi wrote:
> > +	stmmac_disable_all_queues(priv);
> > +
> > +	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++)
> > +		hrtimer_cancel(&priv->tx_queue[chan].txtimer);
> 
> IIRC this hrtimer is to check for completions. Canceling it before
> netif_tx_disable() looks odd, presumably until the queues are stopped
> the timer can get scheduled again, no?
> 

My concern is that at the time hrtimer_cancel is called there may be
some packet that still has to be processed and this cause kernel panic
as stmmac_release free the descriptor (and tx_clean try to free garbage
pointer)

Bu honestly I put the hrtimer_cancel up to be extra safe, the main
problem here was disabling napi polling after tx_disable that I think
was wrong from the start.

> >  	netif_tx_disable(dev);
> >  
> >  	if (device_may_wakeup(priv->device))
> > @@ -3764,11 +3769,6 @@ static int stmmac_release(struct net_device *dev)
> >  	phylink_stop(priv->phylink);
> >  	phylink_disconnect_phy(priv->phylink);
> >  
> > -	stmmac_disable_all_queues(priv);
> > -
> > -	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++)
> > -		hrtimer_cancel(&priv->tx_queue[chan].txtimer);

-- 
	Ansuel

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