Re: frequent lockups in 3.18rc4

From: Dave Jones
Date: Thu Nov 20 2014 - 12:38:39 EST

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.


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