linux-kernel - Re: frequent lockups in 3.18rc4

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Message-ID: <20141120173821.GB9550@redhat.com>
Date:	Thu, 20 Nov 2014 12:38:21 -0500
From:	Dave Jones <davej@...hat.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Don Zickus <dzickus@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	WANG Chao <chaowang@...hat.com>, Baoquan He <bhe@...hat.com>,
	Dave Young <dyoung@...hat.com>
Subject: Re: 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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