Re: [PATCH net] net: usbnet: fix softirq storm on suspend

On Tue, Sep 4, 2012 at 6:36 PM, Bjørn Mork [off-list ref] wrote:

I believe any Ericsson or Gobi modem would do, and most likely other USB
networking devices too.

I haven't explored the gadget.  Doesn't it support remote wakeup?  Well,

No.

it doesn't really have to just for testing this.  You just have to fake
the remote wakeup support, either in the gadget or in the device
driver.  It doesn't matter whether it works or not.  The point is making
the driver suspend the USB device while the network device is running.

The attachment patch is what I have been using to make it support remote
wakeup, and looks it works wrt. runtime PM.

So the code trigging this seems to be


static enum skb_state defer_bh(struct usbnet *dev, struct sk_buff *skb,
                struct sk_buff_head *list, enum skb_state state)
{
        unsigned long           flags;
        enum skb_state          old_state;
        struct skb_data *entry = (struct skb_data *) skb->cb;

        spin_lock_irqsave(&list->lock, flags);
        old_state = entry->state;
        entry->state = state;
        __skb_unlink(skb, list);
        spin_unlock(&list->lock);
        spin_lock(&dev->done.lock);
        __skb_queue_tail(&dev->done, skb);
        if (dev->done.qlen == 1)
                tasklet_schedule(&dev->bh);
        spin_unlock_irqrestore(&dev->done.lock, flags);
        return old_state;
}


Hmm, I should probably dump stack here as well.. Anyway, it's a start.

Maybe a debug message in defer_bh is enough, :-)


Thanks,
--
Ming Lei