Francois Romieu [off-list ref] writes:

OGAWA Hirofumi [off-list ref] :
[...]

quoted

Umm.. the above code is part of ->poll(). I think xxx_interrut() need
netif_running() instead. The driver must clear __LINK_STATE_RX_SCHED
flag...

BTW, ->napi_lock is unneeded because netif_schedule() is already
atomic, it need only local_irq_enable/disable().

Color me confused. The lock is supposed to protect against:

CPU1                         CPU2
[poll]
epic_napi_irq_on(dev, ep);
                             [irq handler]
                             if (netif_rx_schedule_prep(dev)) {
                                     epic_napi_irq_off(dev, ep);
                                     __netif_rx_schedule(dev);
                             }
__netif_rx_complete(dev);

-> napi irq are disabled and device is removed from poll list. What will
   prevent it ?

__LINK_STATE_RX_SCHED flag is setting until __netif_rx_complete() is called.
So netif_rx_schedule_prep() returns 0.

quoted

After __netif_rx_complete() must not do "goto rx_action", otherwise it
may become cause of twice scheduleing, it should move before spin_lock().

 understand the previous statement as:

+               status = inl(ioaddr + INTSTAT);
+               if (status & EpicNapiEvent) {
+                       epic_napi_irq_off(dev, ep);
+                       goto rx_action;
+
+               spin_lock_irqsave(&ep->napi_lock, flags);
+               epic_napi_irq_on(dev, ep);
+               __netif_rx_complete(dev);
+               spin_unlock_irqrestore(&ep->napi_lock, flags);
+

Afaiu, if some data comes in just before the spin_lock, it may wait for ages.

Yes, maybe. But, if after spin_lock, it loop may call the twice
__netif_rx_schedule(). And netif_rx_complete() doesn't call dev_put().
It will leaks the dev->refcnt, I think.

+               __netif_rx_complete(dev);
+               spin_unlock_irqrestore(&ep->napi_lock, flags);

           -- interrupt and call __netif_rx_schedule() --

+               status = inl(ioaddr + INTSTAT);
+               if (status & EpicNapiEvent) {
+                       epic_napi_irq_off(dev, ep);
+                       goto rx_action;

Thanks.
-- 
OGAWA Hirofumi [off-list ref]