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

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Date:	Fri, 18 Jan 2008 14:00:57 +0100
From:	Robert Olsson <Robert.Olsson@...a.slu.se>
To:	David Miller <davem@...emloft.net>
Cc:	Robert.Olsson@...a.slu.se, 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:

 > > 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
 > 
 > Yes, this semaphore thing is highly problematic.  In the most crucial
 > areas where network driver consistency matters the most for ease of
 > understanding and debugging, the Intel drivers choose to be different

 I don't understand the idea with semaphore for enabling/disabling 
 irq's either the overall logic must safer/better without it.  
 
 > The way the napi_disable() logic breaks out from high packet load in
 > net_rx_action() is it simply returns even leaving interrupts disabled
 > when a pending napi_disable() is pending.
 > 
 > This is what trips up the semaphore logic.
 > 
 > Robert, give this patch a try.
 > 
 > In the long term this semaphore should be completely eliminated,
 > there is no justification for it.

 It's on the testing list...

 Cheers
					--ro


 > 
 > Signed-off-by: David S. Miller <davem@...emloft.net>
 > 
 > diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
 > index 0c9a6f7..76c0fa6 100644
 > --- a/drivers/net/e1000/e1000_main.c
 > +++ b/drivers/net/e1000/e1000_main.c
 > @@ -632,6 +632,7 @@ e1000_down(struct e1000_adapter *adapter)
 >  
 >  #ifdef CONFIG_E1000_NAPI
 >  	napi_disable(&adapter->napi);
 > +	atomic_set(&adapter->irq_sem, 0);
 >  #endif
 >  	e1000_irq_disable(adapter);
 >  
 > diff --git a/drivers/net/e1000e/netdev.c b/drivers/net/e1000e/netdev.c
 > index 2ab3bfb..9cc5a6b 100644
 > --- a/drivers/net/e1000e/netdev.c
 > +++ b/drivers/net/e1000e/netdev.c
 > @@ -2183,6 +2183,7 @@ void e1000e_down(struct e1000_adapter *adapter)
 >  	msleep(10);
 >  
 >  	napi_disable(&adapter->napi);
 > +	atomic_set(&adapter->irq_sem, 0);
 >  	e1000_irq_disable(adapter);
 >  
 >  	del_timer_sync(&adapter->watchdog_timer);
 > diff --git a/drivers/net/ixgb/ixgb_main.c b/drivers/net/ixgb/ixgb_main.c
 > index d2fb88d..4f63839 100644
 > --- a/drivers/net/ixgb/ixgb_main.c
 > +++ b/drivers/net/ixgb/ixgb_main.c
 > @@ -296,6 +296,11 @@ ixgb_down(struct ixgb_adapter *adapter, boolean_t kill_watchdog)
 >  {
 >  	struct net_device *netdev = adapter->netdev;
 >  
 > +#ifdef CONFIG_IXGB_NAPI
 > +	napi_disable(&adapter->napi);
 > +	atomic_set(&adapter->irq_sem, 0);
 > +#endif
 > +
 >  	ixgb_irq_disable(adapter);
 >  	free_irq(adapter->pdev->irq, netdev);
 >  
 > @@ -304,9 +309,7 @@ ixgb_down(struct ixgb_adapter *adapter, boolean_t kill_watchdog)
 >  
 >  	if(kill_watchdog)
 >  		del_timer_sync(&adapter->watchdog_timer);
 > -#ifdef CONFIG_IXGB_NAPI
 > -	napi_disable(&adapter->napi);
 > -#endif
 > +
 >  	adapter->link_speed = 0;
 >  	adapter->link_duplex = 0;
 >  	netif_carrier_off(netdev);
 > diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c
 > index de3f45e..a4265bc 100644
 > --- a/drivers/net/ixgbe/ixgbe_main.c
 > +++ b/drivers/net/ixgbe/ixgbe_main.c
 > @@ -1409,9 +1409,11 @@ void ixgbe_down(struct ixgbe_adapter *adapter)
 >  	IXGBE_WRITE_FLUSH(&adapter->hw);
 >  	msleep(10);
 >  
 > +	napi_disable(&adapter->napi);
 > +	atomic_set(&adapter->irq_sem, 0);
 > +
 >  	ixgbe_irq_disable(adapter);
 >  
 > -	napi_disable(&adapter->napi);
 >  	del_timer_sync(&adapter->watchdog_timer);
 >  
 >  	netif_carrier_off(netdev);
 > --
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