linux-kernel - Re: [PATCH net-next 3/3] net: stmmac: Convert to phylink and remove phylib logic

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Date:   Tue, 25 Jun 2019 12:10:15 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Jose Abreu <Jose.Abreu@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     Joao Pinto <Joao.Pinto@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Russell King <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        linux-tegra <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH net-next 3/3] net: stmmac: Convert to phylink and remove
 phylib logic

On 25/06/2019 08:37, Jose Abreu wrote:
> From: Jon Hunter <jonathanh@...dia.com>
> 
>> Any further feedback? I am still seeing this issue on today's -next.
> 
> Apologies but I was in FTO.
> 
> Is there any possibility you can just disable the ethX configuration in 
> the rootfs mount and manually configure it after rootfs is done ?
> 
> I just want to make sure in which conditions this is happening (if in 
> ifdown or ifup).

I have been looking at this a bit closer and I can see the problem. What
happens is that ...

1. stmmac_mac_link_up() is called and priv->eee_active is set to false
2. stmmac_eee_init() is called but because priv->eee_active is false,
   timer_setup() for eee_ctrl_timer is never called.
3. stmmac_eee_init() returns true and so then priv->eee_enabled is set 
   to true.
4. When stmmac_tx_clean() is called because priv->eee_enabled is set to    
   true, mod_timer() is called for the eee_ctrl_timer, but because 
   timer_setup() was never called, we hit the BUG defined at
   kernel/time/timer.c:952, because no function is defined for the 
   timer.

The following fixes it for me ...

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -399,10 +399,13 @@ bool stmmac_eee_init(struct stmmac_priv *priv)
        mutex_lock(&priv->lock);

        /* Check if it needs to be deactivated */
-       if (!priv->eee_active && priv->eee_enabled) {
-               netdev_dbg(priv->dev, "disable EEE\n");
-               del_timer_sync(&priv->eee_ctrl_timer);
-               stmmac_set_eee_timer(priv, priv->hw, 0, tx_lpi_timer);
+       if (!priv->eee_active) {
+               if (priv->eee_enabled) {
+                       netdev_dbg(priv->dev, "disable EEE\n");
+                       del_timer_sync(&priv->eee_ctrl_timer);
+                       stmmac_set_eee_timer(priv, priv->hw, 0, tx_lpi_timer);
+               }
+               mutex_unlock(&priv->lock);
                return false;
        }

It also looks like you have a potention deadlock in the current code
because in the case of if (!priv->eee_active && priv->eee_enabled)
you don't unlock the mutex. The above fixes this as well. I can send a
formal patch if this looks correct. 

Cheers
Jon

-- 
nvpublic