linux-kernel - console_flush_all(): was: : was Re: [PATCH printk v2 10/12] printk: add kthread console printers

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Message-ID: <Yk8XvLJgyIGBuV9w@alley>
Date:   Thu, 7 Apr 2022 18:56:28 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: console_flush_all(): was: : was Re: [PATCH printk v2 10/12] printk:
 add kthread console printers

On Tue 2022-04-05 15:31:33, John Ogness wrote:
> Create a kthread for each console to perform console printing. During
> normal operation (@system_state == SYSTEM_RUNNING), the kthread
> printers are responsible for all printing on their respective
> consoles.
> 
> During non-normal operation, console printing is done as it has been:
> within the context of the printk caller or within irq work triggered
> by the printk caller.
> 
> Console printers synchronize against each other and against console
> lockers by taking the console lock for each message that is printed.
> 
> Signed-off-by: John Ogness <john.ogness@...utronix.de>
> ---
>  include/linux/console.h |   2 +
>  kernel/printk/printk.c  | 262 ++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 252 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/console.h b/include/linux/console.h
> index 8c1686e2c233..9a251e70c090 100644
> --- a/include/linux/console.h
> +++ b/include/linux/console.h
> @@ -2773,6 +2809,10 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
>  	*handover = false;
>  
>  	do {
> +		/* Let the kthread printers do the work if they can. */
> +		if (!allow_direct_printing())
> +			break;

We should return either "true" or "false" here to have predictable
result.

I suggest to return "false". I would mean that the function did not
finish the job as I suggested for the 6th patch.

> +
>  		any_progress = false;
>  
>  		for_each_console(con) {

Best Regards,
Petr