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

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Message-ID: <51b9e2cc3baf61a604bd239b736ec2d12f1f6695.camel@linux.intel.com>
Date:   Thu, 07 Jul 2022 13:45:17 -0700
From:   Todd Brandt <todd.e.brandt@...ux.intel.com>
To:     john.ogness@...utronix.de, pmladek@...e.com
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        senozhatsky@...omium.org, rostedt@...dmis.org
Subject: Re: PNP0501 serial driver takes almost 2 seconds to suspend/resume
 (printk issue)

Adding printk maintainers to the thread


On Thu, 2022-07-07 at 13:31 -0700, Todd Brandt wrote:
> Ever since 5.19.0-rc1 the serial device has taken almost a second
> longer in both suspend and resume. This effect is witnessed in half
> the
> machines in our lab (~10 machines). It occurs on dell, asus, gigabyte
> and other machines so it's not hardware specific.
> 
> I opened a bugzilla issue which includes the git bisect:
> https://bugzilla.kernel.org/show_bug.cgi?id=216216
> 
> 
> Bad commit:
> 
> commit 3b604ca81202eea2a917eb6491e90f610fba0ec7
> Author: John Ogness <john.ogness@...utronix.de>
> Date:   Thu Apr 21 23:28:46 2022 +0206
> 
>     printk: add pr_flush()
> 
>     Provide a might-sleep function to allow waiting for console
> printers
>     to catch up to the latest logged message.
> 
>     Use pr_flush() whenever it is desirable to get buffered messages
>     printed before continuing: suspend_console(), resume_console(),
>     console_stop(), console_start(), console_unblank().
> 
>     Signed-off-by: John Ogness <john.ogness@...utronix.de>
>     Reviewed-by: Petr Mladek <pmladek@...e.com>
>     Signed-off-by: Petr Mladek <pmladek@...e.com>
>     Link: 
> 
https://lore.kernel.org/r/20220421212250.565456-12-john.ogness@linutronix.de
> 
>  include/linux/printk.h |  7 +++++
>  kernel/printk/printk.c | 83
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 90 insertions(+)