Hi,
W dniu 11.05.2020 o 20:29, Dmitry Torokhov pisze:
On Mon, May 11, 2020 at 06:21:13PM +0200, Greg Kroah-Hartman wrote:
On Mon, May 11, 2020 at 03:59:18PM +0200, Andrzej Pietrasiewicz wrote:
Some 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
Cute, but why? Who needs/wants this type of thing?
Surely things that can be done in userspace should be done there.
So we would envision an input daemon which reacts to a predefined
combination of keys. That said, it is not unimaginable to think of
userspace being dead enough (e.g. due to memory pressure) to be unable
to complete such a compound action. In other words userspace not being
able to do it is a good reason for putting the code in the kernel.
Dmitry has given a use case where such a compound action is needed.
Andrzej
On Chrome OS the first time user presses SysRq-X it will try to kill
chrome (and that will cause crash to get uploaded if user consented).
The 2nd time within 5 seconds the same combo is pressed, it will dump
blocked tasks in syslog and try to sync and then panic. On panic the
device will reboot, logs will be scraped from pstore, and uploaded for
analysis.
Thanks.
