linux-kernel - Re: [REGRESSION] disabling and re-enabling magic sysrq fails after kernel 6.11

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Message-ID: <69b6119c-3c3a-406f-9375-3e55fba9b732@heusel.eu>
Date: Sun, 27 Oct 2024 15:06:09 +0100
From: Christian Heusel <christian@...sel.eu>
To: "Ned T. Crigler" <crigler@...il.com>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>, 
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org, regressions@...ts.linux.dev, 
	Jeff LaBundy <jeff@...undy.com>, Benjamin Tissoires <bentiss@...nel.org>
Subject: Re: [REGRESSION] disabling and re-enabling magic sysrq fails after
 kernel 6.11

On 24/10/26 07:15PM, Ned T. Crigler wrote:
> Hi,

Hey Ned,

> It looks like starting with kernel 6.11, disabling and re-enabling
> magic
> sysrq fails with these errors in dmesg:
> 
> kernel: input: input_handler_check_methods: only one event processing
> method can be defined (sysrq)
> kernel: sysrq: Failed to register input handler, error -22
> 
> after doing:
> 
> # echo 0 > /proc/sys/kernel/sysrq
> # echo 438 > /proc/sys/kernel/sysrq
> # echo 0 > /proc/sys/kernel/sysrq
> # echo 438 > /proc/sys/kernel/sysrq
> # echo 0 > /proc/sys/kernel/sysrq
> # echo 438 > /proc/sys/kernel/sysrq

I have found that this issue is also present in the latest mainline
release and bisected it to the following commit:

    d469647bafd9 ("Input: simplify event handling logic")

The additional authors / maintainers have been added to the recipients
lists.

I hope I didn't overlook any pending fixes.

> -- 
> Ned T. Crigler

Cheers,
Chris

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