linux-kernel - Re: [Linux kernel bug] INFO: task hung in blk_mq_get

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Message-ID: <21d52c65-4f18-46a2-be68-ff8487103e82@I-love.SAKURA.ne.jp>
Date: Tue, 14 May 2024 16:39:32 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Sam Sun <samsun1006219@...il.com>, Hillf Danton <hdanton@...a.com>
Cc: linux-kernel@...r.kernel.org, linux-block@...r.kernel.org, axboe@...nel.dk,
        syzkaller-bugs@...glegroups.com, xrivendell7@...il.com
Subject: Re: [Linux kernel bug] INFO: task hung in blk_mq_get_tag

On 2024/05/14 11:05, Sam Sun wrote:
> Pointed out by Tetsuo, this kernel panic might be caused by sending
> NMI between cpus. As dump log shows:

You can do

  # echo 0 > /proc/sys/kernel/hung_task_all_cpu_backtrace

before starting the reproducer in order to disable
trigger_all_cpu_backtrace() from hung task.

If trigger_all_cpu_backtrace() from hung task can reproduce
the kernel panic, I think that trigger_all_cpu_backtrace() from
SysRq-l should be as well able to reproduce the kernel panic.
That is, you can build with CONFIG_MAGIC_SYSRQ=y and try

  # echo l > /proc/sysrq-trigger

for bisecting and reporting as a separate bug.