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SubjectRe: frequent lockups in 3.18rc4
On Thu, Nov 20, 2014 at 11:48:09AM -0500, Vivek Goyal wrote:

> Can we try following and retry and see if some additional messages show
> up on console and help us narrow down the problem.
>
> - Enable verbose boot messages. CONFIG_X86_VERBOSE_BOOTUP=y
>
> - Enable early printk in second kernel. (earlyprintk=ttyS0,115200).
>
> You can either enable early printk in first kernel and reboot. That way
> second kernel will automatically have it enabled. Or you can edit
> "/etc/sysconfig/kdump" and append earlyprintk=<> to KDUMP_COMMANDLINE_APPEND.
> You will need to restart kdump service after this.
>
> - Enable some debug output during runtime from kexec purgatory. For that one
> needs to pass additional arguments to /sbin/kexec. You can edit
> /etc/sysconfig/kdump file and modify "KEXEC_ARGS" to pass additional
> arguments to /sbin/kexec during kernel load. I use following for my
> serial console.
>
> KEXEC_ARGS="--console-serial --serial=0x3f8 --serial-baud=115200"
>
> You will need to restart kdump service.

The only serial port on this machine is usb serial, which doesn't have io ports.

From my reading of the kexec man page, it doesn't look like I can tell
it to use ttyUSB0.

And because it relies on usb being initialized, this probably isn't
going to help too much with early boot.

earlyprintk=tty0 didn't show anything extra after the sysrq-c oops.
likewise, =ttyUSB0

I'm going to try bisecting the problem I'm debugging again, so I'm not
going to dig into this much more today.

Dave



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