Re: 2.4.14-pre8 Alt-SysRq-[TM] failure during lockup...

Eric W. Biederman (ebiederman@lnxi.com)
05 Nov 2001 19:41:38 -0700


"Randy.Dunlap" <rddunlap@osdl.org> writes:

> "Eric W. Biederman" wrote:
> >
> > Summary: I triggered a condition in 2.4.14-pre8 where SysRq triggered
> > but would not print reports. I managed to unstick the condition but
> > had played to much to determine the root cause. My guess is that
> > somehow my default loglevel was messed up. Full information is
> > provided just case I did not muddy the waters too much.
>
> Do you know what the console loglevel was when you tried
> to use Alt-SysRq-M (show_mem) or Alt-SysRq-T (show tasks ==
> show_state)? (first value listed in /proc/sys/kernel/printk file)

I was in single user mode so it shouldn't have been changed
from it's default value. But it might have been.

> show_mem() and show_state() don't modify the current value of
> console_loglevel; they depend on the sysrq handler to do that.
> That value could be too low/small.

Right. That looks to be why I couldn't see my debug information.

There was definentily something hosed at the kernel level
that shouldn't have been. We should be very careful before
we move 2.4.14-pre8 to 2.4.14. Hopefully I/someone can find a way
to reproduce a lockup and track it down.

> Aye, sysrq_handle_term sets console_loglevel to 8 and leaves it there.

That is good to know thanks.

Eric

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