Re: [PATCH] netpoll: WARN_ONCE for start_xmit returns with interrupts enabled

On Wed, 2009-08-19 at 05:43 -0500, Matt Mackall wrote: 

On Wed, 2009-08-19 at 18:43 +0800, DDD wrote:

quoted

The NETPOLL API requires that interrupts remain disabled in
netpoll_send_skb().

Add a WARN_ONCE when ndo_start_xmit returns with interrupts enabled
in netpoll_send_skb().

Signed-off-by: Dongdong Deng <redacted>
---
 net/core/netpoll.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index df30feb..d38103f 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c

@@ -319,6 +319,12 @@ static void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 
 			udelay(USEC_PER_POLL);
 		}
+
+		WARN_ONCE(!irqs_disabled(),
+			KERN_WARNING "netpoll_send_skb(): [net driver %s]"
+			"ndo_start_xmit() shouldn't return with interrupts"
+			"enabled!", dev->name);

Hmm, perhaps:

"netpoll_send_skb(): %s enabled interrupts in poll (%pF)\n",
dev->name, ops->ndo_start_xmit

That'll give us a real function name and maybe even a module name.

Thanks, I will modify it as your suggestions.

When I test the WRAN_ONCE, I find that some net drivers still have this problem,
such as using local_irq_disable/local_irq_enable in ndo_start_xmit() or other cases.


I will do an new patch and hope it could fix this problem completely in all the net drivers that support NETPOLL.


I check the drivers that support NETPOLL one by one again(almost 100 drivers),
and following drivers's fix will be included by my patch:

1: ixp2000/ixpdev.c : 66 local_irq_disable

2: fec_mpc52xx.c : 319 spin_unlock_irq

3: macb.c:602 : 638 spin_unlock_irq

4: mlx4/en_netdev.c : 448 
mlx4_en_xmit() -> mlx4_en_xmit_poll() -> spin_trylock_irq

5: smc91x.c 
It seems that there is a lots work to let smc91x work well with netpoll.


Thanks,
Dongdong