Issue in Kernel docs / Admin Guide / SysRq

Issue in Kernel docs / Admin Guide / SysRq

[Anselm Schüler]

I’m writing here because I don’t know where to find Kernel docs 
(https://docs.kernel.org/) sources and submit patches.

The page “Linux Magic System Request Key Hacks” 
(https://docs.kernel.org/admin-guide/sysrq.html) says this:

“Write a single character to /proc/sysrq-trigger. Only the first 
character is processed, the rest of the string is ignored. However, it 
is not recommended to write any extra characters as the behavior is 
undefined and might change in the future versions. E.g.:
     echo t > /proc/sysrq-trigger”

I interpret the command as a suggestion of how to properly use 
/proc/sysrq-trigger, and not as an example of what not to do, and I 
believe many will share this interpretation. The command as listed will 
write TWO characters to /proc/sysrq-trigger.

Either the behaviour of ignoring \n should be codified and explicitly 
supported or this section should be changed.

Re: Issue in Kernel docs / Admin Guide / SysRq

[Jonathan Corbet]

Anselm Schüler <mail@anselmschueler.com> writes:

> I’m writing here because I don’t know where to find Kernel docs 
> (https://docs.kernel.org/) sources and submit patches.

They are in the Documentation/ directory of the kernel sourc.e

Thanks,

jon

Re: Issue in Kernel docs / Admin Guide / SysRq

[Bagas Sanjaya]

[-- Attachment #1: Type: text/plain, Size: 1508 bytes --]

On Fri, Oct 03, 2025 at 02:32:57PM +0200, Anselm Schüler wrote:
> I’m writing here because I don’t know where to find Kernel docs
> (https://docs.kernel.org/) sources and submit patches.
> 

It's in Documentation/ directory of kernel sources.

If you want to send docs patches, please read
Documentation/process/submitting-patches.rst for how to submit them and make
sure to Cc: linux-doc@vger.kernel.org.

> The page “Linux Magic System Request Key Hacks”
> (https://docs.kernel.org/admin-guide/sysrq.html) says this:
> 
> “Write a single character to /proc/sysrq-trigger. Only the first character
> is processed, the rest of the string is ignored. However, it is not
> recommended to write any extra characters as the behavior is undefined and
> might change in the future versions. E.g.:
>     echo t > /proc/sysrq-trigger”

I think that the second sentence refers to writing subsequent characters in
this context.

> 
> I interpret the command as a suggestion of how to properly use
> /proc/sysrq-trigger, and not as an example of what not to do, and I believe
> many will share this interpretation. The command as listed will write TWO
> characters to /proc/sysrq-trigger.
> 
> Either the behaviour of ignoring \n should be codified and explicitly
> supported or this section should be changed.
> 

See commit 39ff20f5fd4481 ("/proc/sysrq-trigger: accept multiple keys at
once").

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]