netdev - Re: [PATCH net v2] tun: wake up waitqueues after IFF

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Date:   Tue, 18 Jun 2019 10:55:48 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     lifei.shirley@...edance.com
Cc:     jasowang@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, zhengfeiran@...edance.com,
        duanxiongchun@...edance.com
Subject: Re: [PATCH net v2] tun: wake up waitqueues after IFF_UP is set

From: Fei Li <lifei.shirley@...edance.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@...edance.com>
> Acked-by: Jason Wang <jasowang@...hat.com>

Applied and queued up for -stable, thanks.