linux-kernel - Re: How do you investigate the cause of total hang? Is there some information that I should pay attention to in order to get some hint?

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Message-ID: <CAM_iQpWcK1ou9st5QWvdQ7MNfdV09WqjfPB1ASwpoJaBKzJrjQ@mail.gmail.com>
Date:   Tue, 30 Jun 2020 23:06:48 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     孙世龙 sunshilong <sunshilong369@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kernelnewbies <Kernelnewbies@...nelnewbies.org>
Subject: Re: How do you investigate the cause of total hang? Is there some
 information that I should pay attention to in order to get some hint?

On Tue, Jun 30, 2020 at 7:49 PM 孙世龙 sunshilong <sunshilong369@...il.com> wrote:
>
> Hi, list
>
> My x86 machine(linux4.19) sometimes hangs, suddenly not responding in
> any way to the mouse or the keyboard.
>
> How can I investigate why it hung up? Is there extra information I can
> find for a clue? Is there anything less drastic than power-off to get
> some kind of action, if only some limited shell or just beeps,
> but might give a clue?
>

If the hang was a crash which you didn't get a chance to capture the
last kernel log, you can use kdump to collect them. The kernel log
tells what kind of crash it is, a NULL pointer deref, a kernel page fault
etc..

If the hang was a hard lockup, you have to turn on lockup detector
and also kdump to capture what the detector tells.

Thanks.