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

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Message-ID: <YqdTsjRQiJUilSg6@alley>
Date:   Mon, 13 Jun 2022 17:11:46 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Peter Geis <pgwipeout@...il.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 Mon 2022-06-13 04:29:50, John Ogness wrote:
> 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

If the last messages are missing then it is most likely the same
issue.

Peter, could you please try if the patch at
https://lore.kernel.org/r/YqdSw/fJvnkRbjvc@alley
would make any difference?

Best Regards,
Petr