Ubuntu – Kernel freezes on loading ramdisk. How to find out what’s wrong

initrdkernelUbuntu

I'm using an Ubuntu Server (13.04) Minimal installation (with the Xubuntu Metapackage as a desktop environment, if that matters) on x86_64 on my Samsung notebook. I'm currently forced to use the no-longer-maintained version of the proprietary AMD graphics driver (fglrx-legacy) as the open-source "radeon" driver heats the card 15°C more in idle.

That's why I'd really like to try kernel 3.11 with the new power management features for AMD cards. The problem is, once I install a mainline kernel the system freezes after selecting the kernel in Grub with the messages:

Loading Linux 3.11.0-laptop ...
Loading initial ramdisk ...

And nothing happens. How can I find out what's wrong? Are there any logs from that early in the boot process stored somewhere?

Some more information: The system works perfectly with the Ubuntu Raring Kernel self-compiled from Git (which is based on 3.8). It doesn't work with mainline Kernel 3.9 or 3.10 (same problem). I also tried a pre-compiled "generic" version of 3.10, doesn't work either. I have 4 partitions on the hard drive: /boot (unencrypted), /, /home and swap (all LUKS/dm-crypt encrypted). The notebook is a Samsung NP-R522H. The GPU is a Mobility Radeon HD 4650.

Best Answer

Potential Problem?

You problem sounds like it's related to this particular issue with Samsung laptops + UEFI + Linux.

http://www.pcworld.com/article/2027819/not-just-linux-windows-can-brick-samsung-laptops-too.html

Further Research

I searched on your particular model # and did not find anything that jumped out as a potential source of your issue. So I do not think it's a widely know issue at least at this point, so your next course of action is to debug the issue.

Debugging a Kernel

Here are the order of things to try.

verbose

During the boot phase, add the following kernel parameter to the list.
```
linux ..... verbose
```
debug

If the verbose argument doesn't shed any light the next level to check is debug.
```
linux ..... debug
```
others

There are several levels beyond that, but let's not get ahead of ourselves. Let's try the above first and see if they show where the Kernel is hanging.

References

Related Solutions

Linux – What’s changed with USB drivers in 4.0 and later Linux kernels

This sounds like a kernel regression in 4.x Linux, at least for your specific hardware.

http://archlinuxarm.org/forum/viewtopic.php?f=53&t=8798

It may be in this commit, but it's hard to say since you didn't provide any further information about your system.

https://github.com/torvalds/linux/commit/a0b5cd4ac2d6542d524d8063961bf914b5df1efa

Some systems apparently are seeing issues with at least USB 3: https://lists.debian.org/debian-kernel/2015/08/msg00066.html

So the real question is, what is your hardware, and what is the latest 4.x kernel you have tried. This may have been resolved in a recent 4.x release. Is the issue with usb 2 and 3, or just 3, or not related to usb version? That will help narrow it down. Your data looks like it's just usb2 max on your system.

Kernel regressions are normal.

As I tell people when they ask this type of question, a new linux kernel has several possible outcomes:

something that didn't work before works now
everything stayed the same on your system
something that worked before, stopped working
some things got better, and some things stopped working

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1455376 That's an Ubuntu bug with usb handling.

Usually bugs that impact things a lot of people use will get fixed relatively rapidly, so it's worth checking the latest release of the latest stable kernel, which I think is at 4.3 at the moment.

If you use ubuntu, you can run the liquorix kernel, at least if it's current ubuntu, not LTS, same for debian, non stable releases.

Seeing: inxi -bxxx would be helpful to show the basics of your system. inxi is installable from most distro repositories.

Here's Greg KH's list of USB changes for 4.0 / 3.20

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e29876723f7cb7728f0d6a674d23f92673e9f112

  usb: musb: fix device hotplug behind hub
  usb: dwc2: Fix a bug in reading the endpoint directions from reg.
  staging: emxx_udc: fix the build error
  usb: Retry port status check on resume to work around RH bugs
  Revert "usb: Reset USB-3 devices on USB-3 link bounce"
  uhci-hub: use HUB_CHAR_*
  usb: kconfig: replace PPC_OF with PPC
  ehci-pci: disable for Intel MID platforms (update)
  usb: gadget: Kconfig: use bool instead of boolean
  usb: musb: blackfin: remove incorrect __exit_p()
  USB: fix use-after-free bug in usb_hcd_unlink_urb()
  ehci-pci: disable for Intel MID platforms
  usb: host: pci_quirks: joing string literals
  USB: add flag for HCDs that can't receive wakeup requests (isp1760-hcd)
  USB: usbfs: allow URBs to be reaped after disconnection
  cdc-acm: kill unnecessary messages
  cdc-acm: add sanity checks
  usb: phy: phy-generic: Fix USB PHY gpio reset
  usb: dwc2: fix USB core dependencies
  usb: renesas_usbhs: fix NULL pointer dereference in dma_release_channel()

http://kernelnewbies.org/Linux_4.0 shows the full change set.

https://lkml.org/lkml/2015/6/26/511 that's the changes in USB for 4.2-rc1. As you can see, asking 'what has changed' is not probably the exact right question, more useful would be to determine if the issue has been resolved for your hardware yet in the latest releases.

Linux – How to find out a linux kernel ring buffer size

Regarding the size, it's recorded in your kernel's config file. For example, on Amazon EC2 here, it's 256 KiB.

# grep CONFIG_LOG_BUF_SHIFT /boot/config-`uname -r`
CONFIG_LOG_BUF_SHIFT=18
# perl -e 'printf "%d KiB\n",(1<<18)/1024'
256 KiB
#

Referenced in /kernel/printk/printk.c

#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)

More information in /kernel/trace/ring_buffer.c

Note that if you've passed a kernel boot param "log_buf_len=N" (check using cat /proc/cmdline) then that overrides the value in the config file.