linux-kernel - Re: Stack trace when removing Thunderbolt devices while kernel shutting down

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Message-ID: <20200218150124.stvsj2rozxrgxw2h@wunner.de>
Date:   Tue, 18 Feb 2020 16:01:24 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: Stack trace when removing Thunderbolt devices while kernel
 shutting down

On Tue, Feb 18, 2020 at 02:18:40PM +0000, Nicholas Johnson wrote:
> If I surprise remove Thunderbolt 3 devices just as the kernel is 
> shutting down, I get stack dumps, when those devices would not normally 
> cause stack dumps if the kernel were not shutting down.
> 
> Because the kernel is shutting down, it makes it difficult to capture 
> the logs without a serial console.

Hold a camera in front of the screen and try to capture the messages
as an MP4 movie which can be uploaded to YouTube or something.

If the output moves too fast to capture it, artificially slow it down
by adding a udelay() to call_console_drivers() in kernel/printk/printk.c.

Thanks,

Lukas