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SubjectRe: help: sysrq and X
Eyal Lebedinsky <eyal@eyal.emu.id.au> wrote:
>
> I am trying to diagnose a hard lockup. The only way I can reproduce it is
> with mythtv. When the system locks up (no mouse, no activity in X, no message
> logged) I can use magic sysrq, but I cannot see the output.
>
> Using 'r' does not enable console switching. However 'b' will boot the
> system, and I hope 's' and 'u' did something blindly.
>
> I there a way to regain a text console in order to inspect the kernel?
>
> I can connect a machine to the serial port if this will help - does
> sysrq work though the serial port? Which software should I use on
> the serial port (on the 'other' machine) for this purpose then?

Yes, serial console is the best way to do this. Add `console=ttyS0' to the
kernel boot command line and use `<break>t' to get an all-task backtrace.

If you're using minicom (spit) on the other end, Control-A F t is the
combination to use.

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