Maxime Haselbauer posted on Thu, 15 May 2014 22:16:48 +0200 as excerpted:
> I am using kde since 2010 There has been continuously a problem with a > given component of KDE that I won't even mentionn it but basically the > problem is like that: > 1)you work 2)and suddenly a programm starts to rev-up at 100% cpu and > your computer does not respond anymore until you press the shutdown > button > > My questions: > 1) Is it currently possible to have like an "emegency" button so that > when this happen you would press on it, it would freeze everything and > head you back to a terminal immediatly where you can kill those mother > fuckers Basically it would be like ctrl+alt+f1 but ctrl+alt+f1 does not > respond as well when something is running at 100% cpu... First, please tone down your language a bit. It's quite possible there are kids or other sensitive folks subscribed, and it's also quite possible to express frustration using the traditional YELLING and *YELLING* *EVEN* *LOUDER* methods without such language. Or if you /really/ feel the need, use "comic swearing": *#@#_%. It gets the message across. =8^0 Meanwhile... As vgobbo says, try the "magic sys-request" sequences. But here's a bit more detail and additional sequence suggestions: Wikipedia on SysRQ: https://en.wikipedia.org/wiki/System_request Quote of interest: >> On the later [x86] 101-key keyboard, it shares a physical key with the >> Print Screen key function. One must hold down the Alt key while >> pressing this “dual-function” key to invoke SysRq. Thus the alt-srq sequence. To that, a third key is added, depending on the desired action. Wikipedia on the Linux-specific ' "Magic SysRq key": https://en.wikipedia.org/wiki/Magic_SysRq_key The kernel's own magic-srq document can be found at $KERNDIR/Documentation/sysrq.txt (where $KERNDIR is /usr/src/linux or wherever else you or your distro places your kernel sources directory). Assuming magic-srq is enabled (or enable-able) on your distro, the most common use, as the above page explains, is REISUB (assuming QWERTY keyboard layout, there's a table on the wiki page for other common layouts), to effect a safer emergency reboot, when nothing else seems to work. Additionally, how far you have to go in that sequence before you get any indication that it's helping is a good indication of how horribly locked up the system actually was/is. If the RE gets a response, it wasn't too bad. OTOH, if you get all the way to the B before anything (including drive activity indication) happens, the kernel was corrupted badly enough that it feared it couldn't safely even write to storage to sync and remount-read-only, which means things were pretty bad, and if even the B doesn't respond, then the kernel itself was locked up, to the point it couldn't even see or process the unconditional reboot directive. REISUB: unRaw - Turn off X's raw keyboard mode tErm - Terminate all processes that will terminate gracefully kIll - Force-kill all remaining processes Sync - Flush all unwritten data to storage (disk/SSD) remoUnt - Remount all filesystems read-only reBoot - Unconditional immediate reboot Note that unlike the other keys in the REISUB sequence, alt-srq-s (sync) by itself is generally safe at any time and can be used to force-flush unwritten data to disk before an operation you think might crash the computer. You can then continue as if nothing happened, and/or repeatedly hit alt-srq-s in ordered to repeatedly sync an ongoing operation. I use it that way myself from time to time. Meanwhile, of particular interest for this thread is another magic-srq key, the K/saK/Secure-access-key, alt-srq-k. This key kills any process listening on the current virtual terminal along with all its children. As a result, it can be used to force-kill an unresponsive X, if necessary. It may or may not return you to a shell prompt (tho if it doesn't, sometimes using the alt-srq-r/unraw, followed by the usual ctrl- alt-Fn sequence, to switch to a different VT, can sometimes help). This is what I might well try if I found myself in the situation you describe, since 100% CPU will very likely still respond to magic-srq, and the alt-srq-k combo has a good chance of killing X and either letting it respawn (if you use a *DM graphical login) or getting you back a text login (if as me you login at a text terminal and run startx to start kde). The above references should get you started if you're interested in more, and of course a google on "magic sysrequest" and variants should turn up a wealth of community commentary as well. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman ___________________________________________________ This message is from the kde mailing list. Account management: https://mail.kde.org/mailman/listinfo/kde. Archives: http://lists.kde.org/. More info: http://www.kde.org/faq.html.
