Hello Prabhu, your mail formatting is somehow distorted. However, I will try to answer anyway: * On Wed, May 11, 2011 at 11:03:29PM +0530 Prabhu nath wrote:
My grub.conf is title Fedora (2.6.34) root (hd0,1) kernel /vmlinuz-2.6.34 ro root=UUID=4a51e22e-ec12-469f-80ff-17afe3e6f15f rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYTABLE=us console=tty0 kgdbwait kgdb8250=ttyS0,115200 [...] The result was, on booting up the kernel kgdb was not waiting.
Here, the command line parameter are wrong. First: kgdb8250 is called kgdboc now. Second: Order matters. You must specify kgdbwait AFTER kgdboc in order for it to take effect.
Scenario 2. I connected a null modem cable from C1 to C2. Tested the cable by redirecting the kernel boot logs from C1 to C2 thru the cable and cable is fine. I connected C1 to a LCD monitor (console=tty0) through a VGA cable so that I tty0 to view normal kernel booting logs and null modem cable to work with debugger My grub.conf is title Fedora (2.6.34) root (hd0,1) kernel /vmlinuz-2.6.34 ro root=UUID=4a51e22e-ec12-469f-80ff-17afe3e6f15f rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYTABLE=us console=tty0 kgdbwait kgdboc=ttyS0,115200 initrd /initramfs-2.6.34.img The result is, on booting up the kernel kgdb is waiting for the input ( This log was seen on my LCD monitor) but Alt-SysRq-g did not work here to switch to the debugger
Is it really waiting? I could not get it to work unless I switched the order of kgdbwait and kgdboc. I think I also found it written somewhere on the net that order matters here. Now, regarding sysrq: - What is the output of: # cat /proc/sys/kernel/sysrq Either specify a 1, or a bit mask which selectively switches everything on. -OR- add "kernel.sysrq = 1" to /etc/sysctl.conf. Having said this, Alt-Sysrq-g does not work for me, either! But: # echo g > /proc/sysrq-trigger Works for me. I have not yet figured out why this is. Having said all this: Do you want to use the magic sysrq to initially break into the debugger? This does not work, and it is not necessary (if you switch the order of kgdboc and kgdbwait).
Scenario 3: I connected a null modem cable from C1 to C2. Tested the cable by redirecting the kernel boot logs from C1 to C2 thru the cable and cable is fine. My grub.conf is title Fedora (2.6.34) root (hd0,1) kernel /vmlinuz-2.6.34 ro root=UUID=4a51e22e-ec12-469f-80ff-17afe3e6f15f rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYTABLE=us console=ttyS0,115200n8 kgdbwait kgdboc=ttyS0,115200 kgdbcon
I never tried to have the console and kgdboc on the same serial port. Is this even supposed to work? BTW, your idea about writing an article on how I set it up is a good idea. I will try to find the time to do so. HTH Spiro. -- Spiro R. Trikaliotis http://opencbm.sf.net/ http://www.trikaliotis.net/ http://www.viceteam.org/