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Date:   Thu, 11 Mar 2021 17:40:50 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Xie He <xie.he.0141@gmail.com>
Cc:     Martin Schiller <ms@dev.tdt.de>,
        "David S. Miller" <davem@davemloft.net>,
        Linux X25 <linux-x25@vger.kernel.org>,
        Linux Kernel Network Developers <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net] net: lapbether: Prevent racing when checking
 whether the netif is running
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On Thu, 11 Mar 2021 16:28:47 -0800 Xie He wrote:
> On Thu, Mar 11, 2021 at 4:10 PM Jakub Kicinski <kuba@kernel.org> wrote:
> >
> > And the "noqueue" queue is there because it's on top of hdlc_fr.c
> > somehow or some out of tree driver? Or do you install it manually?  
> 
> No, this driver is not related to "hdlc_fr.c" or any out-of-tree
> driver. The default qdisc is "noqueue" for this driver because this
> driver doesn't set "tx_queue_len". This means the value of
> "tx_queue_len" would be 0. In this case, "alloc_netdev_mqs" will
> automatically add the "IFF_NO_QUEUE" flag to the device, then
> "attach_one_default_qdisc" in "net/sched/sch_generic.c" will attach
> the "noqueue" qdisc for devices with the "IFF_NO_QUEUE" flag.

I see.