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From:   =?UTF-8?B?5p2O6I+y?= <lifei.shirley@bytedance.com>
Date:   Thu, 20 Jun 2019 00:02:26 +0800
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Subject: Re: [External Email] Re: [PATCH net v2] tun: wake up waitqueues after
 IFF_UP is set
To:     David Miller <davem@davemloft.net>
Cc:     Jason Wang <jasowang@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, zhengfeiran@bytedance.com,
        duanxiongchun@bytedance.com
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Thanks.

Have a nice day
Fei

On Wed, Jun 19, 2019 at 1:55 AM David Miller <davem@davemloft.net> wrote:
>
> From: Fei Li <lifei.shirley@bytedance.com>
> Date: Mon, 17 Jun 2019 21:26:36 +0800
>
> > Currently after setting tap0 link up, the tun code wakes tx/rx waited
> > queues up in tun_net_open() when .ndo_open() is called, however the
> > IFF_UP flag has not been set yet. If there's already a wait queue, it
> > would fail to transmit when checking the IFF_UP flag in tun_sendmsg().
> > Then the saving vhost_poll_start() will add the wq into wqh until it
> > is waken up again. Although this works when IFF_UP flag has been set
> > when tun_chr_poll detects; this is not true if IFF_UP flag has not
> > been set at that time. Sadly the latter case is a fatal error, as
> > the wq will never be waken up in future unless later manually
> > setting link up on purpose.
> >
> > Fix this by moving the wakeup process into the NETDEV_UP event
> > notifying process, this makes sure IFF_UP has been set before all
> > waited queues been waken up.
> >
> > Signed-off-by: Fei Li <lifei.shirley@bytedance.com>
> > Acked-by: Jason Wang <jasowang@redhat.com>
>
> Applied and queued up for -stable, thanks.