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Date:   Mon, 13 Jun 2022 12:49:03 +0900
From:   Sergey Senozhatsky <senozhatsky@chromium.org>
To:     John Ogness <john.ogness@linutronix.de>
Cc:     Sergey Senozhatsky <senozhatsky@chromium.org>,
        Petr Mladek <pmladek@suse.com>,
        Peter Geis <pgwipeout@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>
Subject: Re: [BUG] Threaded printk breaks early debugging
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On (22/06/13 01:08), John Ogness wrote:
> On 2022-06-12, Sergey Senozhatsky <senozhatsky@chromium.org> wrote:
> > Should a situation when we have only one online CPU be enough of a
> > reason to do direct printing? Otherwise we might not have CPUs to
> > wakeup khtread on, e.g. when CPU that printk is in atomic section for
> > too long.
> 
> IMHO, no. Especially in that situation, we do not want printk causing
> that atomic section to become even longer. If the machine has entered
> normal operation, we want printk out of the way.

At the same time printk throttles itself in such cases: new messages are
not added at much higher pace that they are printed at. So we lower the
chances of missing messages.