From: Olaf Kirch <[EMAIL PROTECTED]>
Date: Wed, 4 Jul 2007 14:16:32 +0200
Another locking bug in netpoll, why am I not surprised? :-/
Thanks for reporting this Olaf.
> I think the only real fix for this is to restrict who is allowed
> to remove the interface from the poll_list. Only net_rx_action
> should be allowed to do so. A possible patch is given below
> (beware, it's untested so far)
I'm happy to entertain this kind of solution, but we really
need to first have an interface to change multiple bits
at a time in one atomic operation, because by itself this
patch doubles the number of atomices we do when starting
a NAPI poll.
> static inline int __netif_rx_schedule_prep(struct net_device *dev)
> {
> + /* The driver may have decided that there's no more work
> + * to be done - but now another interrupt arrives, and
> + * we changed our mind. */
> + smp_mb__before_clear_bit();
> + clear_bit(__LINK_STATE_RX_COMPLETE, &dev->state);
> +
> return !test_and_set_bit(__LINK_STATE_RX_SCHED, &dev->state);
> }
>
Because of that change.
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