On Fri, Oct 02, 2020 at 03:42:52PM +0200, Andrzej Pietrasiewicz wrote:
Hi,
W dniu 02.10.2020 o 14:54, Greg Kroah-Hartman pisze:
On Tue, Aug 18, 2020 at 01:28:25PM +0200, Andrzej Pietrasiewicz wrote:
Userland might want to execute e.g. 'w' (show blocked tasks), followed by 's' (sync), followed by 1000 ms delay and then followed by 'c' (crash) upon a single magic SysRq. Or one might want to execute the famous "Raising Elephants Is So Utterly Boring" action. This patch adds a configurable handler, triggered with 'C', for this exact purpose. The user specifies the composition of the compound action using syntax similar to getopt, where each letter corresponds to an individual action and a colon followed by a number corresponds to a delay of that many milliseconds, e.g.:
ws:1000c
or
r:100eis:1000ub
A macro language for sysrq commands, who would have thought...
Anyway, _why_ would userland want to do something so crazy as this? What is the use-case here?
A use-case is Chromebooks which do want to execute 'w', 's', wait 1000ms and then 'c' under one key combination. Having that supported upstream brings us one little step closer to those machines running upstream kernel.
Who is causing that to "execute"? Some daemon/program?
Another argument for such a "macro language" is when a machine's system keeps degrading over time, possibly degrading (relatively) fast. "Raising Elephants Is So Utterly Boring" consists of 6 actions, each of which requires pressing several keys. The user might be unable to complete all the 6 steps, while a "macro" requires user's involvement for carrying out just one step.
So you want to "preload" some commands ahead of time, for when you get in trouble?
These should just be debugging / last resort types of things, how regular are they being used in your systems?
thanks,
greg k-h