netdev - Re: [PATCH,v2,net-next 1/2] tun: enable NAPI for TUN/TAP driver

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Date:   Fri, 22 Sep 2017 14:03:05 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>
Cc:     Petar Penkov <peterpenkov96@...il.com>,
        linux-netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        David Miller <davem@...emloft.net>,
        Petar Bozhidarov Penkov <ppenkov@...nford.edu>
Subject: Re: [PATCH,v2,net-next 1/2] tun: enable NAPI for TUN/TAP driver

On Fri, Sep 22, 2017 at 1:11 PM, Mahesh Bandewar (महेश बंडेवार)
<maheshb@...gle.com> wrote:
>>  #ifdef CONFIG_TUN_VNET_CROSS_LE
>>  static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
>>  {
>> @@ -541,6 +604,11 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
>>
>>         tun = rtnl_dereference(tfile->tun);
>>
>> +       if (tun && clean) {
>> +               tun_napi_disable(tun, tfile);
> are we missing synchronize_net() separating disable and del calls?

That is not needed here. napi_disable has its own mechanism for waiting
until a napi struct is no longer run. netif_napi_del will call synchronize_net
if needed. These two calls are made one after the other in quite a few drivers.