linux-kernel - Re: RE: [PATCH 1/2] printk: nbcon: move locked_port flag to struct uart

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Message-ID: <20240125133523.W7aDeBqt@linutronix.de>
Date: Thu, 25 Jan 2024 14:35:23 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: "Chang, Junxiao" <junxiao.chang@...el.com>
Cc: John Ogness <john.ogness@...utronix.de>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"rostedt@...dmis.org" <rostedt@...dmis.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Li, Hao3" <hao3.li@...el.com>, "Li, Lili" <lili.li@...el.com>,
	"Gao, Jianfeng" <jianfeng.gao@...el.com>,
	"linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>
Subject: Re: RE: [PATCH 1/2] printk: nbcon: move locked_port flag to struct
 uart_port

On 2024-01-25 01:08:24 [+0000], Chang, Junxiao wrote:
> 
> Issue could be reproduced with our hardware every time. My cmdline is:
> BOOT_IMAGE=(hd0,gpt2)/boot/bzImage-linux-intel-iot-lts-rt-6.6-kernel
> root=PARTLABEL=primary rootwait console=ttyS0,115200 console=tty0
> init=/sbin/preinit-env console=ttyS4,115200n8 console=ttyS5,115200n8
> 
> If you would like to try any debug patch with my ADL hardware, please feel free to let me know.
> 
> For console pointer sharing issue, from code logic point of view, the call chain looks like:
> serial8250_register_8250_port -> uart_add_one_port -> serial_ctrl_register_port -> serial_core_register_port -> serial_core_add_one_port
> 
> In API serial_core_add_one_port, uart_port's console pointer is assigned with driver's console pointer:
> 	uport->cons = drv->cons;
> Driver's console pointer points to static structure "univ8250_console" which is defined in 8250_core.c
> 
> That is, all 8250 serial devices' console pointer are same, they point to univ8250_console.

Okay, So that I see this and the unbalanced acquire/ release part with
the attached patch. I leave it to John…
Btw. You don't see kernel log output on ttyS4 + ttyS5, right? Just a
login prompt.
…
> Thanks,
> Junxiao

Sebastian