linux-kernel - Re: [PATCH v9] /proc/sysrq-trigger: accept multiple keys at once

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Date:   Mon, 20 Nov 2023 08:45:37 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Tomas Mudrunka <tomas.mudrunka@...il.com>
Cc:     corbet@....net, gregkh@...uxfoundation.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org, rdunlap@...radead.org
Subject: Re: [PATCH v9] /proc/sysrq-trigger: accept multiple keys at once

On 15. 11. 23, 11:34, Tomas Mudrunka wrote:
> Just for convenience.
> This way we can do:
> `echo _reisub > /proc/sysrq-trigger`
> Instead of:
> `for i in r e i s u b; do echo "$i" > /proc/sysrq-trigger; done;`
> 
> This can be very useful when trying to execute sysrq combo remotely
> or from userspace. When sending keys in multiple separate writes,
> userspace can be killed before whole combo is completed.
> Therefore putting all keys in single write is more robust approach.
> 
> Signed-off-by: Tomas Mudrunka <tomas.mudrunka@...il.com>
> ---
> V8 -> V9: Fixed english bit more

Please check my comments to v6 more carefully once again. Plus:

> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -1150,16 +1150,28 @@ EXPORT_SYMBOL(unregister_sysrq_key);
>   #ifdef CONFIG_PROC_FS
>   /*
>    * writing 'C' to /proc/sysrq-trigger is like sysrq-C
> + * Normally only the first character written is processed.

Normally, <-- comma

> + * If first character is underscore, all characters are processed.

the first
an underscore

Maybe it would make sense to prepend "However, " to this very sentence?

thanks,
-- 
js
suse labs