linux-kernel - Re: PNP0501 serial driver takes almost 2 seconds to suspend/resume (printk issue)

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Date:   Sun, 10 Jul 2022 22:10:45 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     todd.e.brandt@...ux.intel.com, Petr Mladek <pmladek@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: PNP0501 serial driver takes almost 2 seconds to suspend/resume
 (printk issue)

On 2022-07-10, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>> Looking at freeze-5.19.0-rc1-bad.html, at 3431.221039 we see that
>> suspend_console() was called. The additional 1-second delay you are
>> referring to would be 3432.436187, where serial is
>> suspended. pr_flush() would have been satisfied when the message at
>> 3431.221039 was printed. So the question is, why is there still
>> printing going on?
>
> It might be no_console_suspend hack. Are you, btw, aware of this ugly
> hack in the kernel?

I am aware of it. There are some cases where it actually works. But it
is not being used here. The boot args are:

BOOT_IMAGE=/boot/vmlinuz-5.19.0-rc1+ root=UUID=1dfec046-baf6-4f38-8b5e-a8f438a48038 ro rw quiet console=ttyS0,115200 console=tty0 i915.enable_psr=1 initcall_debug log_buf_len=32M quiet splash console=tty0 console=ttyS0,115200n8 vt.handoff=7

I am curious if Todd sees this problem with 5.19-rc4 or later (the
kthread printers were removed).

John