RE: [EXT] Re: [PATCH tty/serial 1/1] tty: serial: imx: fix sysrq lockdep issue

[Andy Duan <fugang.duan@xxxxxxx>]

From: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> Sent: Friday, November 22, 2019 6:34 PM
> Hello,
> 
> On Fri, Nov 22, 2019 at 10:00:53AM +0000, Andy Duan wrote:
> > From: Fugang Duan <fugang.duan@xxxxxxx>
> >
> > commit dbdda842fe96 ("printk: Add console owner and waiter logic to
> > load balance console writes") introduces the lockdep issue for imx
> > serial driver in sysrq case:
> >      CPU0                    CPU1
> >      ----                    ----
> > lock(&port_lock_key);
> >                              lock(console_owner);
> >                              lock(&port_lock_key);
> > lock(console_owner);
> >
> > It should unlock port_lock_key in handle_sysrq().
> 
> I already discussed this problem some time ago but then failed to complete
> the topic. You might want to look at the old discussion, see
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.s
> pinics.net%2Flists%2Fkernel%2Fmsg3266353.html&amp;data=02%7C01%7Cf
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> ed=0.
> 
> Best regards
> Uwe

Thanks for point out the old discussion.
The issue seems exist all most of serial drivers. It is better to fix it on common code.

How about the next step, we hope to the lockdep issue is fixed ASAP. 
Thanks!

Regards,
Fugang
> 
> --
> Pengutronix e.K.                           | Uwe Kleine-König
> |
> Industrial Linux Solutions                 |
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