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Message-ID: <87y1y48spg.fsf@jogness.linutronix.de>
Date: Fri, 10 Jun 2022 17:11:15 +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
Hi Peter,
On 2022-06-10, Peter Geis <pgwipeout@...il.com> wrote:
> However I've run into an issue debugging early boot issues. Anything
> that causes the kernel threading system to die (for example here, a
> NPE) causes the boot console to halt before it outputs the error.
A null pointer exception should trigger a panic, which will cause printk
to enter direct mode for the oops. It should be just as effective as
before introducing the printing kthreads.
Can you please provide a test case or patch that will trigger the
problem you refer to?
> Would it be possible to have both a kconfig option and a runtime
> option to toggle printk_fallback_preferred_direct()? Currently I've
> had to force it at all times while debugging.
It would be trivial to provide a boot parameter for this behavior, but I
think we first need to see a real problem and also see if we can fix
that problem.
John Ogness
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