On Fri, Oct 02, 2020 at 05:06:54PM +0200, Andrzej Pietrasiewicz wrote: > Hi, > > W dniu 02.10.2020 o 16:02, Greg Kroah-Hartman pisze: > > 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? > > No, as far as I know they patch the kernel to change the behavior > of Sysrq-x combination, so the "execution" is triggered by the user. So this isn't coming from the chromeos team, so there is no guarantee that they will switch to this if it is merged? > > > 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 > It can be said this way, yes. > > > > > These should just be debugging / last resort types of things, how > > regular are they being used in your systems? > > > > The "REISUB" itself is a kind of a last resort thing. > > It is true that it's not a very frequent situation, but does its being rare > preclude having such a function in the kernel? > > While preparing this patch I wanted it to be flexible, but perhaps it is > too flexible for some reason? If the permissions of the module_param's > sysfs entry were changed to 0444 would it be better? Then the compound > action would still be configurable but only at boot time rather than at > boot time _and_ runtime. I don't have an issue with it happening at runtime and boot time, just that this is adding additional complexity to the kernel (parsers are fun!) for no real-world user. thanks, greg k-h _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
