lkml.org 
[lkml]   [2020]   [Jul]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
SubjectRE: UART/TTY console deadlock
Date
Hi All,

Can we land this patch upstream?
Feel free to add my tested-by.

Thanks.

Regards,
Shirish S

-----Original Message-----
From: S, Shirish <Shirish.S@amd.com>
Sent: Wednesday, July 1, 2020 12:15 PM
To: Tony Lindgren <tony@atomide.com>; Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>; Andy Shevchenko <andy.shevchenko@gmail.com>; Raul Rangel <rrangel@google.com>; Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>; linux-kernel <linux-kernel@vger.kernel.org>; Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Andy Shevchenko <andriy.shevchenko@linux.intel.com>; kurt@linutronix.de; S, Shirish <Shirish.S@amd.com>; Peter Zijlstra <peterz@infradead.org>; John Ogness <john.ogness@linutronix.de>; Steven Rostedt <rostedt@goodmis.org>
Subject: Re: UART/TTY console deadlock


On 6/30/2020 11:32 PM, Tony Lindgren wrote:
> * Sergey Senozhatsky <sergey.senozhatsky@gmail.com> [200630 13:06]:
>> On (20/06/30 14:22), Petr Mladek wrote:
> ...
>
>>>>>> @@ -2284,8 +2289,6 @@ int serial8250_do_startup(struct uart_port *port)
>>>>>> * allow register changes to become visible.
>>>>>> */
>>>>>> spin_lock_irqsave(&port->lock, flags);
>>>>>> - if (up->port.irqflags & IRQF_SHARED)
>>>>>> - disable_irq_nosync(port->irq);
>>>>>>
>>>>>> wait_for_xmitr(up, UART_LSR_THRE);
>>>>>> serial_port_out_sync(port, UART_IER, UART_IER_THRI); @@
>>>>>> -2297,9 +2300,9 @@ int serial8250_do_startup(struct uart_port *port)
>>>>>> iir = serial_port_in(port, UART_IIR);
>>>>>> serial_port_out(port, UART_IER, 0);
>>>>>>
>>>>>> - if (port->irqflags & IRQF_SHARED)
>>>>>> - enable_irq(port->irq);
>>>>>> spin_unlock_irqrestore(&port->lock, flags);
>>>>>> + if (irq_shared)
>>>>>> + enable_irq(port->irq);
>>>>>>
>>>>>> /*
>>>>>> * If the interrupt is not reasserted, or we otherwise
>>>>> I think that it might be safe but I am not 100% sure, sigh.
>>>> Yeah, I'm not 100%, but I'd give it a try.
>>> I do not feel brave enough to ack it today. But I am all for trying
>>> it if anyone more familiar with the code is fine with it.
>> I see. Well, I suppose we need Ack-s from tty/serial/8250 maintainers.
>> I would not be very happy if _only_ printk people Ack the patch.

FWIW, the lockdep trace is not seen anymore with the patch applied.

Regards,

Shirish S

> This conditional disable for irq_shared does not look nice to me from
> the other device point of view :)
>
> Would it be possible to just set up te dummy interrupt handler for the
> startup, then change it back afterwards? See for example
> omap8250_no_handle_irq().
>
> The other device for irq_shared should be capable of dealing with
> spurious interrupts if it's shared.
>
> Regards,
>
> Tony

--
Regards,
Shirish S

\
 
 \ /
  Last update: 2020-07-02 05:49    [W:0.159 / U:0.604 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site