linux-kernel - Re: [PATCH printk v1] printk: Avoid irq_work for printk

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Message-ID: <aSCOR56F8zbgzDHs@pathway.suse.cz>
Date: Fri, 21 Nov 2025 17:07:35 +0100
From: Petr Mladek <pmladek@...e.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sherry Sun <sherry.sun@....com>, Jacky Bai <ping.bai@....com>,
	Jon Hunter <jonathanh@...dia.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Derek Barbosa <debarbos@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH printk v1] printk: Avoid irq_work for printk_deferred()
 on suspend

On Fri 2025-11-21 11:26:00, John Ogness wrote:
> With commit ("printk: Avoid scheduling irq_work on suspend") the
> implementation of printk_get_console_flush_type() was modified to
> avoid offloading when irq_work should be blocked during suspend.
> Since printk uses the returned flush type to determine what
> flushing methods are used, this was thought to be sufficient for
> avoiding irq_work usage during the suspend phase.
> 
> However, vprintk_emit() implements a hack to support
> printk_deferred(). In this hack, the returned flush type is
> adjusted to make sure no legacy direct printing occurs when
> printk_deferred() was used.
> 
> Because of this hack, the legacy offloading flushing method can
> still be used, causing irq_work to be queued when it should not
> be.
> 
> Adjust the vprintk_emit() hack to also consider
> @console_irqwork_blocked so that legacy offloading will not be
> chosen when irq_work should be blocked.
> 
> Link: https://lore.kernel.org/lkml/87fra90xv4.fsf@jogness.linutronix.de
> Signed-off-by: John Ogness <john.ogness@...utronix.de>

JFYI, the patch has been committed into printk/linux.git,
branch rework/suspend-fixes.

Best Regards,
Petr