Re: [PATCH] tty: ldisc: fix deadlock between ldisc_sem and rtnl_mutex

[Zhou, Yun]

Hi Jagielski,

On 7/16/26 15:59, Jagielski, Jedrzej wrote:
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> From: Yun Zhou <yun.zhou@xxxxxxxxxxxxx>
> Sent: Thursday, July 16, 2026 8:47 AM
>
> > syzbot reported a circular lock dependency involving tty ldisc_sem and
> > the networking rtnl_mutex. The full chain is:
> >
> >   rtnl_mutex --> nft_commit_mutex --> ... --> ep->mtx --> ldisc_sem --> rtnl_mutex
>
> still unclear where the first mutex may come from

  tty_set_ldisc()
    tty_ldisc_lock()        <- hold ldisc_sem
      tty_ldisc_open()
        slcan_open()
          register_candev()
            register_netdev()
              rtnl_net_lock_killable()  <- hold rtnl_mutex

> > +      tty_ldisc_unlock(tty);
> >
> > +      /*
>
> this blank line is redundant i believe

Isn't it common practice to leave the first line of a multi-line comment 
blank? Does it violate the coding style guidelines?

BR,
Yun