linux-kernel - Re: [REGRESSION] 2.6.24-rc7: e1000: Detected Tx Unit Hang

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Date:	Wed, 16 Jan 2008 18:07:38 +0100
From:	Robert Olsson <Robert.Olsson@...a.slu.se>
To:	David Miller <davem@...emloft.net>
Cc:	elendil@...net.nl, jesse.brandeburg@...el.com,
	slavon@...telecom.ru, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [REGRESSION] 2.6.24-rc7: e1000: Detected Tx Unit Hang


David Miller writes:
 > > On Wednesday 16 January 2008, David Miller wrote:
 > > > Ok, here is the patch I'll propose to fix this.  The goal is to make
 > > > it as simple as possible without regressing the thing we were trying
 > > > to fix.
 > > 
 > > Looks good to me. Tested with -rc8.
 > 
 > Thanks for testing.

 Yes that code looks nice. I'm using the patch but I've noticed another 
 phenomena with the current e1000 driver. There is a race when taking a 
 device down at high traffic loads. I've tracked and instrumented and it 
 seems like occasionly irq_sem can get bump up so interrupts can't be 
 enabled again.


eth0 e1000_irq_enable sem = 1    <- High netload
eth0 e1000_irq_enable sem = 1
eth0 e1000_irq_enable sem = 1
eth0 e1000_irq_enable sem = 1
eth0 e1000_irq_enable sem = 1
eth0 e1000_irq_enable sem = 1
eth0 e1000_irq_enable sem = 1    <- ifconfig eth0 down
eth0 e1000_irq_disable sem = 2

**e1000_open                     <- ifconfig eth0 up
eth0 e1000_irq_disable sem = 3      Dead. irq's can't be enabled
e1000_irq_enable miss
eth0 e1000_irq_enable sem = 2
e1000_irq_enable miss
eth0 e1000_irq_enable sem = 1
ADDRCONF(NETDEV_UP): eth0: link is not ready


Cheers
					--ro

static void
e1000_irq_disable(struct e1000_adapter *adapter)
{
        atomic_inc(&adapter->irq_sem);
        E1000_WRITE_REG(&adapter->hw, IMC, ~0);
        E1000_WRITE_FLUSH(&adapter->hw);
        synchronize_irq(adapter->pdev->irq);

        if(adapter->netdev->ifindex == 3)
        printk("%s e1000_irq_disable sem = %d\n",  adapter->netdev->name,
               atomic_read(&adapter->irq_sem));
}

static void
e1000_irq_enable(struct e1000_adapter *adapter)
{
        if (likely(atomic_dec_and_test(&adapter->irq_sem))) {
                E1000_WRITE_REG(&adapter->hw, IMS, IMS_ENABLE_MASK);
                E1000_WRITE_FLUSH(&adapter->hw);
                }
        else
                printk("e1000_irq_enable miss\n");

        if(adapter->netdev->ifindex == 3)
          printk("%s e1000_irq_enable sem = %d\n",  adapter->netdev->name,
                 atomic_read(&adapter->irq_sem));
}
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