Re: [Xen-devel] net: Detect drivers that reschedule NAPI and exhaust budget

[David Miller <davem@xxxxxxxxxxxxx>]

From: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Date: Fri, 19 Dec 2014 17:34:48 -0800

>> @@ -4620,7 +4620,11 @@ static void net_rx_action(struct softirq_action *h)
>>                                       */
>>                                      napi_gro_flush(n, HZ >= 1000);
>>                              }
>> -                            list_add_tail(&n->poll_list, &repoll);
>> +                            /* Some drivers may have called napi_schedule
>> +                             * prior to exhausting their budget.
>> +                             */
>> +                            if (!WARN_ON_ONCE(!list_empty(&n->poll_list)))
>> +                                    list_add_tail(&n->poll_list, &repoll);
>>                      }
>>              }
>>  
> 
> I do not think stack trace will point to the buggy driver ?
> 
> IMO it would be better to print a single line with the netdev name ?

Right, we are already back from the poll routine and will just end
up seeing the call trace leading to the software interrupt.


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