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

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Message-ID: <YqVWL3gpfV9HJBLe@google.com>
Date:   Sun, 12 Jun 2022 11:57:51 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Peter Geis <pgwipeout@...il.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        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 (22/06/10 11:34), Peter Geis wrote:
> > 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.
> 
> This might be a side effect of the fact that this is on a low powered
> arm64 board. I noticed with threading enabled during large bursts the
> console drops an excessive amount of messages. It's especially
> apparent during the handover from earlycon to the normal console.

How many CPUs does it have?