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Date:   Wed, 12 Aug 2020 08:19:57 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     peterz@...radead.org,
        Maciej ┼╗enczykowski <maze@...gle.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Alex Belits <abelits@...vell.com>,
        Nitesh Narayan Lal <nitesh@...hat.com>
Subject: Re: [PATCH net] net: accept an empty mask in
 /sys/class/net/*/queues/rx-*/rps_cpus



On 8/12/20 1:00 AM, peterz@...radead.org wrote:
> On Tue, Aug 11, 2020 at 06:45:23PM -0700, Maciej ┼╗enczykowski wrote:
>> On Tue, Aug 11, 2020 at 6:34 PM Eric Dumazet <edumazet@...gle.com> wrote:
>>
>>> We must accept an empty mask in store_rps_map(), or we are not able
>>> to disable RPS on a queue.
>>>
>>> Fixes: 07bbecb34106 ("net: Restrict receive packets queuing to
>>> housekeeping CPUs")
>>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>>> Reported-by: Maciej ┼╗enczykowski <maze@...gle.com>
>>> Cc: Alex Belits <abelits@...vell.com>
>>> Cc: Nitesh Narayan Lal <nitesh@...hat.com>
>>> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
>>> ---
>>>  net/core/net-sysfs.c | 12 +++++++-----
>>>  1 file changed, 7 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>>> index
>>> 9de33b594ff2693c054022a42703c90084122444..efec66fa78b70b2fe5b0a5920317eb1d0415d9e3
>>> 100644
>>> --- a/net/core/net-sysfs.c
>>> +++ b/net/core/net-sysfs.c
>>> @@ -757,11 +757,13 @@ static ssize_t store_rps_map(struct netdev_rx_queue
>>> *queue,
>>>                 return err;
>>>         }
>>>
>>> -       hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
>>> -       cpumask_and(mask, mask, housekeeping_cpumask(hk_flags));
>>> -       if (cpumask_empty(mask)) {
>>> -               free_cpumask_var(mask);
>>> -               return -EINVAL;
>>> +       if (!cpumask_empty(mask)) {
>>> +               hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
>>> +               cpumask_and(mask, mask, housekeeping_cpumask(hk_flags));
>>> +               if (cpumask_empty(mask)) {
>>> +                       free_cpumask_var(mask);
>>> +                       return -EINVAL;
>>> +               }
>>>         }
> 
> Ah indeed! Sorry about that.
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> 

No worries, thanks for the review guys.

We probably should add a test doing something like

echo ffffffff >/sys/class/net/lo/queues/rx-0/rps_cpus
echo 0 >/sys/class/net/lo/queues/rx-0/rps_cpus

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