Re: [BUG 2.6.0-test11] pcnet32 oops

On Fri, Dec 05, 2003 at 04:59:00PM -0800, David S. Miller wrote:

This is the classic case of doing disabling/enabling of software
interrupts with hardware interrupts disabled, which is a bug.

In this case pcnet32_set_multicast_list() is disabling hardware
interrupts, and the packet freeing of pcnet32_purge_tx_ring()
is what leads to the software interrupt disable/enable.

I think the root cause of this problem is that pcnet32_set_multicast_list()
dumps the entire TX ring on the floor (as a side effect of calling
pcnet32_restart()). I don't think dev->set_multicast_list() is supposed to
do that.

However, I'm inclined to believe that we should change dev_kfree_skb_any()
to fix this class of problems, by making it check for hardware interrupts
being disabled as well as being in an interrupt.

I've been wondering about this too with the recent netpoll patches. Many
(including pcnet32) implement the poll controller simply as

	disable_irq (dev->irq);
	driver_interrupt_handler (dev->irq, dev, NULL);
	enable_irq (dev->irq);

If the interrupt handler calls dev_kfree_skb_any(), could you then run into
this kind of problem? Or is it just if you call spin_lock_irq*() that you
have a problem?

-- 
Regards,
Rask Ingemann Lambertsen