linux-kernel - Re: [PATCHSET] ptrace,signal: group stop / ptrace updates

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 28 Jan 2011 13:36:50 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Anca Emanuel <anca.emanuel@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	Tejun Heo <tj@...nel.org>, roland@...hat.com, oleg@...hat.com,
	jan.kratochvil@...hat.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCHSET] ptrace,signal: group stop / ptrace updates

* Anca Emanuel (anca.emanuel@...il.com) wrote:
> On Fri, Jan 28, 2011 at 7:41 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> > On Fri, 28 Jan 2011, Ingo Molnar wrote:
> >> See that '^C^C' line? That is where i had to do Ctrl-C twice.
> >>
> >> It only fails here about once every 10 times, so it's very rare. I have a stock F14
> >> system running on that box, with the very latest .38 based kernel.
> >
> > Tripped over the refuse ^C thing today twice. Had to kill a kernel
> > build from another shell. It just happily displayed ^C and never
> > stopped. That happens once in a while and I have no idea either how to
> > debug that.
> 
> cc: Mathieu
> 
> Use lttng ?

Heh :) I'm sure Ingo and Thomas have their own tools for that ;) There is
one extra thing in the LTTng instrumentation that can help solve this problem:
the "input subsystem" instrumentation (enabled with ltt-armall -i). You can then
get a dump of:

- Your keystrokes (you can then grep for your ctrl-c input)
- Read/poll/select system calls (so you know when your terminal receives the
  input).
- Signals sent/delivered

Some of these are already instrumented in the mainline kernel, so you might get
away without the input subsystem instrumentation.

If I had to take a wild guess, my bet would be to take a look in the area of
signal delivery, but you never know, maybe it's a userspace bug in the X
terminal emulator code that is causing this weirdness.

Hope this helps,

Mathieu

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/