Subject: Re: [RFC PATCH 07/13] net: sched: support qdisc_reset on NOLOCK qdisc

From: John Fastabend <[email-masked]>
Date: Wed, 17 Aug 2016 15:59:32 -0700

On 16-08-17 03:53 PM, Eric Dumazet wrote:
> On Wed, 2016-08-17 at 12:36 -0700, John Fastabend wrote:
>> The qdisc_reset operation depends on the qdisc lock at the moment
>> to halt any additions to gso_skb and statistics while the list is
>> free'd and the stats zeroed.
> 
> ...
> 
>> Signed-off-by: John Fastabend <[email-masked]>
>> ---
>>  net/sched/sch_generic.c |   45 +++++++++++++++++++++++++++++++++++----------
>>  1 file changed, 35 insertions(+), 10 deletions(-)
>>
>> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
>> index 3b9a21f..29238c4 100644
>> --- a/net/sched/sch_generic.c
>> +++ b/net/sched/sch_generic.c
>> @@ -737,6 +737,20 @@ void qdisc_reset(struct Qdisc *qdisc)
>>  	kfree_skb(qdisc->skb_bad_txq);
>>  	qdisc->skb_bad_txq = NULL;
>>  
>> +	if (qdisc->gso_cpu_skb) {
>> +		int i;
>> +
>> +		for_each_possible_cpu(i) {
>> +			struct gso_cell *cell;
>> +
>> +			cell = per_cpu_ptr(qdisc->gso_cpu_skb, i);
>> +			if (cell) {
>> +				kfree_skb_list(cell->skb);
>> +				cell = NULL;
> 
> 	You probably wanted :
> 			cell->skb = NULL;
> 

Yep thanks!

> 
>> +			}
>> +		}
>> +	}
>> +
>>  	if (qdisc->gso_skb) {
>>  		kfree_skb_list(qdisc->gso_skb);
>>  		qdisc->gso_skb = NULL;
>> @@ -812,10 +826,6 @@ struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
>>  	root_lock = qdisc_lock(oqdisc);
>>  	spin_lock_bh(root_lock);
>>  
>> -	/* Prune old scheduler */
>> -	if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1)
>> -		qdisc_reset(oqdisc);
>> -
>>  
> 
> This probably belongs to a separate patch, before any per cpu / lockless
> qdisc changes ?
> 
> 
> 

Agreed will do for next rev thanks for reviewing.