Subject: bug#12478: cat SEGV when I press Ctrl-Alt-SysRq-1 on text console

From: "Alan Curry" <[email-masked]>
Date: Mon, 1 Oct 2012 05:36:55 -0500 (GMT+5)

Rafal W. writes:
> 
> So in example if I want to check all currently held Locks with SysRq-D
> (which doesn't work anyway), so:
> When I press SysRq-D, I've KSnapshot popping up. In the text console
> it doesn't work at all.

ksnapshot sounds like something that might respond to a PrtSc keypress. This
is a sign that you aren't using Alt, so what you've really done is PrtSc-D.
Didn't I tell you already to stop using "SysRq" to descibe key combinations
that don't include Alt? WITHOUT ALT IT IS NOT A SYSRQ KEY. Got that yet?
Reread it until you do.

> When I press Control-SysRq-D, my session is getting logout.

Well, Ctrl-D is EOF and PrtSc+D is a meaningless combination (as meaningless
as pressing D and Q at the same time, it's anyone's guess which will take
precedence)

> When I press Control-Alt-SysRq-D my processes are killed.

Too many keys there, I can't guess what they're all doing. Get rid of the
Control. And make sure your kernel has CONFIG_LOCKDEP, otherwise the Sysrq+D
function is disabled.

Also, based on the Subject line, you think "SEGV" is a synonym for core dump.
Stop thinking that. Nothing segfaulted. SIGSEGV is one of many signals that
can cause a core dump. SIGQUIT is another one.

-- 
Alan Curry