linux-kernel - Re: [PATCH -next] panic: complete the flush of the hard deadlock log messages to the serial port

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Message-Id: <20201123115235.74aab2449ac5cf27f10a4cfd@linux-foundation.org>
Date:   Mon, 23 Nov 2020 11:52:35 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Xu Qiang <xuqiang36@...wei.com>
Cc:     <keescook@...omium.org>, <mingo@...nel.org>,
        <peterz@...radead.org>, <mcgrof@...nel.org>, <huyue2@...ong.com>,
        <yangtiezhu@...ngson.cn>, <will@...nel.org>, <aquini@...hat.com>,
        <gpiccoli@...onical.com>, <aik@...abs.ru>,
        <linux-kernel@...r.kernel.org>, <rui.xiang@...wei.com>
Subject: Re: [PATCH -next] panic: complete the flush of the hard deadlock
 log messages to the serial port

On Mon, 23 Nov 2020 13:13:59 +0000 Xu Qiang <xuqiang36@...wei.com> wrote:

> when hardlockup_all_cpu_backtrace is on, and there are
> a large number of cores in the system, it takes
> a long time to output the hard deadlock logs of all cores
> to the serial port. When the console_flush_on_panic function
> in panic is executed, console_locked is still held.
> As a result, garbled characters are displayed in the serial port log.
> 
> To solve this problem, wait for a maximum of 10s for the serial port
> to be released before console_flush_on_panic.

Wouldn't it be better to wait until all the printing of all those
backtraces has completed?