Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
From:   John Ogness <john.ogness@linutronix.de>
To:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Petr Mladek <pmladek@suse.com>
Cc:     Sergey Senozhatsky <senozhatsky@chromium.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-amlogic@lists.infradead.org
Subject: Re: [PATCH printk v5 1/1] printk: extend console_lock for
 per-console locking
In-Reply-To: <51dfc4a0-f6cf-092f-109f-a04eeb240655@samsung.com>
References: <20220421212250.565456-1-john.ogness@linutronix.de>
 <20220421212250.565456-15-john.ogness@linutronix.de>
 <878rrs6ft7.fsf@jogness.linutronix.de> <Ymfgis0EAw0Oxoa5@alley>
 <Ymfwk+X0CHq6ex3s@alley>
 <CGME20220427070833eucas1p27a32ce7c41c0da26f05bd52155f0031c@eucas1p2.samsung.com>
 <2a82eae7-a256-f70c-fd82-4e510750906e@samsung.com>
 <Ymjy3rHRenba7r7R@alley>
 <b6c1a8ac-c691-a84d-d3a1-f99984d32f06@samsung.com>
 <87fslyv6y3.fsf@jogness.linutronix.de>
 <51dfc4a0-f6cf-092f-109f-a04eeb240655@samsung.com>
Date:   Sat, 30 Apr 2022 18:06:01 +0206
Message-ID: <87k0b6blz2.fsf@jogness.linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On 2022-04-29, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
> The same issue happens if I boot with init=/bin/bash

Very interesting. Since you are seeing all the output up until you try
doing something, I guess receiving UART data is triggering the issue.

> I found something really interesting. When lockup happens, I'm still
> able to log via ssh and trigger any magic sysrq action via
> /proc/sysrq-trigger.

If you boot the system and directly login via ssh (without sending any
data via serial), can you trigger printk output on the UART? For
example, with:

    echo hello > /dev/kmsg

(You might need to increase your loglevel to see it.)

> It turned out that the UART console is somehow blocked, but it
> receives and buffers all the input. For example after issuing "echo
>  >/proc/sysrq-trigger" from the ssh console, the UART console has been 
> updated and I see the magic sysrq banner and then all the commands I 
> blindly typed in the UART console! However this doesn't unblock the
> console.

sysrq falls back to direct printing. This would imply that the kthread
printer is somehow unable to print.

> Here is the output of 't' magic sys request:
>
> https://pastebin.com/fjbRuy4f

It looks like the call trace for the printing kthread (pr/ttyAML0) is
corrupt.

Could you post your kernel config?

John