linux-kernel - Re: [BUG] Threaded printk breaks early debugging

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Date:   Mon, 13 Jun 2022 04:29:50 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     Peter Geis <pgwipeout@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>
Subject: Re: [BUG] Threaded printk breaks early debugging

On 2022-06-12, Peter Geis <pgwipeout@...il.com> wrote:
> The buffer isn't an issue here, everything is available in dmesg when
> userspace becomes available. Instead some messages bound for the
> serial console are never output.

OK. Good to know.

> We run a serial console at 1.5m baud which is significantly higher
> than most SoCs which default to 115200. I have noticed some timing
> differences since the introduction of the threaded console. A
> significant amount of information is dumped very early in the boot
> process (between 0 and 4 seconds into boot), as most drivers are
> probing during this time. It also happens to be when the earlycon
> console hands over to the normal console. There is no abnormal
> debugging enabled, the output is a standard (non-quiet) boot log. The
> question is why is direct mode not triggering during a panic?

Just to be clear, you are not losing any intermediate messages. Only the
tail end of the kernel log was never printed. Is this correct?

This may be the same issue being discussed here [0].

John Ogness

[0] https://lore.kernel.org/all/87v8t5l39z.fsf@jogness.linutronix.de