Subject: Re: [PATCH net] net: sched: fix panic in rate estimators

From: John Fastabend <[email-masked]>
Date: Sat, 31 Jan 2015 20:45:02 -0800

On 01/31/2015 05:55 PM, David Miller wrote:
> From: Eric Dumazet <[email-masked]>
> Date: Thu, 29 Jan 2015 17:30:12 -0800
>
>> From: Eric Dumazet <[email-masked]>
>>
>> Doing the following commands on a non idle network device
>> panics the box instantly, because cpu_bstats gets overwritten
>> by stats.
>>
>> tc qdisc add dev eth0 root <your_favorite_qdisc>
>> ... some traffic (one packet is enough) ...
>> tc qdisc replace dev eth0 root est 1sec 4sec <your_favorite_qdisc>
>   ...
>> Lets play safe and not use an union : percpu 'pointers' are mostly read
>> anyway, and we have typically few qdiscs per host.
>>
>> Signed-off-by: Eric Dumazet <[email-masked]>
>> Cc: John Fastabend <[email-masked]>
>> Fixes: 22e0f8b9322c ("net: sched: make bstats per cpu and estimator RCU safe")
>
> Applied and queued up for -stable, thanks Eric.
>

Thanks Eric, looks like my "replace" test scripts never sent traffic
before the replace call.

Also I haven't seen any RCU splats in awhile so I'll send out a patch
to drop the qdisc_lock on ing_filter shortly.

-- 
John Fastabend         Intel Corporation