[uml-devel] Is there an easy way to do a stack dump on UML?

[uml-devel] Is there an easy way to do a stack dump on UML?

[Rob Landley]

I don't know how to send sysrq through the stdio console.

I have a reproducable hang (well, I did this morning and think I can recreate 
it).  It's gcc 4.0.2 attempting to statically link busybox (the allyesconfig 
version), it just goes off into la-la land.  left it for an hour and no 
progress, and UML is not eating noticeable CPU according to top (it roughly 
correlates with the timer interrupt load).

I'd like to see what the heck this sucker thinks it's doing, but it's kinda 
tricky to strace "make".  (Too many forks.)

Rob
-- 
Steve Ballmer: Innovation!  Inigo Montoya: You keep using that word.
I do not think it means what you think it means.


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Re: [uml-devel] Is there an easy way to do a stack dump on UML?

[Blaisorblade]

On Friday 02 December 2005 21:12, Rob Landley wrote:
> I don't know how to send sysrq through the stdio console.

uml_mconsole $umid sysrq or "sysrq" at the uml_mconsole $umid prompt? sysrq 
$let is for the $let sysrq.

> I have a reproducable hang (well, I did this morning and think I can
> recreate it).  It's gcc 4.0.2 attempting to statically link busybox (the
> allyesconfig version), it just goes off into la-la land.  left it for an
> hour and no progress, and UML is not eating noticeable CPU according to top
> (it roughly correlates with the timer interrupt load).

> I'd like to see what the heck this sucker thinks it's doing, but it's kinda
> tricky to strace "make".  (Too many forks.)

> Rob

-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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Re: [uml-devel] Is there an easy way to do a stack dump on UML?

[Rob Landley]

On Friday 02 December 2005 20:59, Blaisorblade wrote:
> On Friday 02 December 2005 21:12, Rob Landley wrote:
> > I don't know how to send sysrq through the stdio console.
>
> uml_mconsole $umid sysrq or "sysrq" at the uml_mconsole $umid prompt? sysrq
> $let is for the $let sysrq.

I've never used mconsole.  Never needed it before.

Perhaps if I attach to a serial console instead of stdio I can send sysrq that 
way...

Rob
-- 
Steve Ballmer: Innovation!  Inigo Montoya: You keep using that word.
I do not think it means what you think it means.


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Re: [uml-devel] Is there an easy way to do a stack dump on UML?

[Jeff Dike]

On Fri, Dec 02, 2005 at 09:44:20PM -0600, Rob Landley wrote:
> I've never used mconsole.  Never needed it before.
> 
> Perhaps if I attach to a serial console instead of stdio I can send sysrq that 
> way...

No.  Just think a little.  Banging on the SysRq key on your keyboard can't
do anything but send SysRq to the host.

SysRq for a virtual machine has to be an out-of-band thing wrt the host.  For
UML, that's mconsole.

				Jeff


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Re: [uml-devel] Is there an easy way to do a stack dump on UML?

[Rob Landley]

On Saturday 03 December 2005 00:00, Jeff Dike wrote:
> On Fri, Dec 02, 2005 at 09:44:20PM -0600, Rob Landley wrote:
> > I've never used mconsole.  Never needed it before.
> >
> > Perhaps if I attach to a serial console instead of stdio I can send sysrq
> > that way...
>
> No.  Just think a little.  Banging on the SysRq key on your keyboard can't
> do anything but send SysRq to the host.

I know.  That's why I asked.  I thought there might be some other key 
combination that could do the same thing for a UML console.  (QEMU listens to 
the tty to do various escapes in non-graphics mode, for example.)

> SysRq for a virtual machine has to be an out-of-band thing wrt the host. 

Yeah, sending compressed data across the console becomes a bit dangerous 
otherwise.  But again, the difference between a pipe and a tty is that a tty 
has out-of-band information attached.

Possibly a couple of different shift keys plus the character in question?  
(Something X wouldn't intercept first, qemu uses ctrl-alt and it seems to 
work for them.)  According to man 4 console_ioctl, TIOCLINUX subcode 6 gives 
me something called "shift_state", so maybe I can beat some information out 
of the tty to tell when the user hit "ctrl-alt t" and turn that into sysrq-t?  
In theory it might work both when stdin is a tty and via an xterm...

To-do item.  The documentation on this sucks pretty badly...

> For UML, that's mconsole.

Except that serial consoles can also do sysrq.  (I vaguely remember they send 
a break signal or some such.  Dunno how to do that on an emulated one...)

>     Jeff

Rob
-- 
Steve Ballmer: Innovation!  Inigo Montoya: You keep using that word.
I do not think it means what you think it means.


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