On 11/20/14 at 12:38pm, Dave Jones wrote: > 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.
Enabling ttyUSB0 still need hacks in dracut/kdump module to pack the usb serial ko to initramfs and load it early. We can work on it in Fedora because it may benefit to some late problems. > > 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 earlyprintk=vga instead of tty0? earlyprintk=efi in case efi boot. earlyprintk=dbgp sometimes also helps but it's a little hard to setup because we need a usb debugger. My nokia n900 works well as a debugger. But to find a usable usb debug port in native host might fail, so this is my last try for earlyprintk :( > > I'm going to try bisecting the problem I'm debugging again, so I'm not > going to dig into this much more today. > Another case what I know about kdump kernel issue is nouveau sometimes does not work So if this is the case you can try add "rd.driver.blacklist=nouveau" to field KDUMP_COMMANDLINE_APPEND in /etc/sysconfig/kdump. Or just add "nomodeset" in 1st kernel grub cmdline so that 2nd kernel will reuse it to avoid load drm modules and also earlyprintk=vga probably could show something. Thanks Dave -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
