On the other side of cloud

Tags:kernel linux madwifi module

After upgrading to madwifi svn (now released 0.9.3), I found I encountered maybe a seldom problem: the linux kernel module loading order.

In the latest madwifi, it provides three different rate control algorithms, ONOE, AMRR and SAMPLE, instead of only SAMPLE in the previous version. Though SAMPLE is the most advanced one and is used by default, the other two must have ability to take over it’s job. So modules dependency relationship can’t be hardcode into source. But when you insert these modules to /etc/modules for kernel loading when booting, the kernel will take ath_pci first, which depends on ath_rate_sample or other rate control modules. So, the ath_pci can’t be loaded completely success but was still loaded, and reports:

Unable to load needed module: ath_rate_sample; no support for automatic module loading<3>Error loading module “ath_rate_sample”

Then, if you still want to use it, you must reload ath_pci manually, for ath_rate_sample is loaded after ath_pci, but the former didn’t know it, and it can’t specify ath_rate_sample as its depend modules for this can be specify when it was loading.

UPDATE: Thank Matt tell me the real reason: The “automatic module loading” wasn’t open when we compiling the kernel (and in fact error message tell me of that clearly…).
So, please recompile your kernel with “automatic modules loading”(CONFIG_KMOD=y), and recompile your madwifi modules with your new kernel. Then try to load it normally. It’s more useful…
It seems silly to try to load these modules manually… I’m sorry…

SO PLEASE FORGET THE THING BELOW EXCEPT YOU REALLY ENCOUNTER SOME UGLY MODULES…

The only method to solve this is to specify the kernel modules loading order, but the loading order seems can’t be specify simply by /etc/modules (I checked module-init-tools, but don’t understand why it don’t load the modules by order — it meant to do it…). So I add a script in /etc/init.d/ to do this, and link it to /etc/rcS.d/S21load-madwifi.sh(just after module-init-tools)

1 #!/bin/bash
2 #load-madwifi.sh
3
4 modprobe -r ath_pci
5 modprobe -r wlan_tkip
6 modprobe -r wlan_scan_sta
7 modprobe -r ath_rate_sample
8
9 modprobe ath_rate_sample
10 modprobe wlan_scan_sta
11 modprobe wlan_tkip
12 modprobe ath_pci

If you are a debian user, you can simply use:

sudo modconf –load-before ath_rate_sample –load-before \
wlan_scan_sta –load-before wlan_tkip –load-only ath_pci

That’s it.

Tags:kernel linux pae xen

I am trying to install xen on my debian a week ago, but failed because of that damn PAE build-in debian kernel for xen and my poor Pentium-M without PAE. Today I retried to install xen(now the version is 3.0.4) from source. Follow the README in the package, everything goes well except extremely long time waiting for kernel compiling - it filled kernel with all kinds of driver modules…

I went with option KERNELS=”linux-2.6-xen0 linux-2.6-xenU” first, everything goes well. But when I try to customize kernel and build a linux-2.6-xen kernel(not only a dom0, but also a an unprivileged guest kernel), and reboot it, I found I encountered this:

VFS: Cannot open root device “hda7″ or unknown-block(0,0)
Please append a correct “root=” boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on
unknown-block(0,0) (XEN) Domain 0 crashed: rebooting machine in 5
seconds. (XEN) Domain 0 crashed: rebooting machine in 5 seconds.

I double checked my /boot/grub/menu.lst, and it was written correctly. So I looked it for google, and mailing list of xen-users told me that:

The -xen kernel is built with almost all drivers configured as modules; hence you’ll need an initrd including the driver[s] for your scsi or ide controller so you can mount the root filesystem.

So what I have to do is add a initrd for my xen kernel. But later I found that mkinitrd which mentioned in README is out of date. According to the Debian Wiki, debian have switched from initrd to initramfs. So another tool is introduced. Offical debian kernel package needs initramfs to preload modules that the kernel didn’t build in but as a module(e.g. ext3, ide, input device), just like the case linux-2.6-xen.

It’s easy to get a initramfs with yaird(and also mkinitramfs can be used too, which appears to be more widely used). Yaird’s configure file located at /etc/yarid, but almost nothing need modified in my case. So I only run following command as a sudoer:

yaird –verbose –output=/boot/initrd.img-xen 2.6.16.33-xen

And appended the following line to the xen’s section in /boot/grub/menu.lst:

title Xen 3.0.4 / XenLinux 2.6.16.33
root (hd0,6)
kernel /boot/xen-3.0.gz
module /boot/vmlinuz-2.6.16-xen root=/dev/hda7 ro console=tty0
module /boot/initrd.img-xen

Take care of “module”. It isn’t “initrd”, for xen take over the kernel while booting.

And reboot, everything goes well with your customize kernel.

Tags:script vim

Many times when I using my old blog system, I fell in bad mood when I have to mix my source code with content, or no support for source code like syntax highlighted. And when I use vim’s script TOhtml to deal with these thing, I feel that it’s handy, but still not enough convenient. I have to choose and copy the html code by my hand, then add a something like <quoteblock class=”vimblock”>(”vimblock” is a user-defined CSS element, will be mention later) tag to differentiate these code from common <quoteblock>. It’s too inconvenient, also seems easy to be done with a script. So I wrote this.

The script based on TOhtml written by Bram Moolenarr. It convert the current selection to html using TOhtml, then get the body of html and wrap it with <blockquote class=”vimblock”>. In the end, it send the wrapped section of syntax code to clipboard for the further use.
Usage: You need specify CSS for using the code generate by this script.
The default CSS of your schema can be generated by TOhtml, though it will only generate the elements that used by current file, you can find a file with most kinds of elements to generate the basis and modify it when you need more elements.
After generation, just copy the section between <!– –> just below the <style type=”text/css”>, replace element name “body” with “.vimblock” and append it to your CSS file( usually style.css).
After have well defined your CSS, you can use the V and :Yankcode and paste to use this script.

Thanks for the support from Yuxuan ‘fishy’ Wang.

The script can be found at here. And my relate style.css selection is shown below:

1 /* for vim :TOhtml */
2 .vimblock { margin-left: 1.5em;
3 padding-left: 5px;
4 border: 1px dotted #ccc;
5 border-left: 5px solid #ccc;
6 color: #ffffff;
7 background-color: #000000;}
8 .lnr { color: #ffff00; font-weight: bold; }
9 .Underlined { color: #80a0ff; text-decoration: underline; }
10 .Special { color: #ffa500; }
11 .Comment { color: #80a0ff; }
12 .Identifier { color: #40ffff; }
13 .Statement { color: #ffff60; font-weight: bold; }
14 .Constant { color: #ffa0a0; }
15 .Type { color: #60ff60; font-weight: bold; }
16 .PreProc { color: #ff80ff; }
17 .Title { color: #ff00ff; font-weight: bold; }
18 .Error { color: #ff0000; background-color: #000000; }

Tags:debian kernel pae xen

Recently I bought a two-hand T41 with Pentium-M 1.6G. Today I am trying to install xen on my debian (etch). But I am failed by following the regular step on debianwiki, for the reason that pentium-m didn’t support PAE which used to manage >4G memories. I think I don’t have so many memories, so I want to install a xen without pae (and I noticed that it’s curious apt installed package with pae by default), which is package “xen-hypervisor-3.0.3-1-i386″. And kernel package is “linux-image-2.6.18-4-xen-686 “. But I still failed after reboot. It reports that “PAE mode mismatch between Xen and DOM0 (xen=no, dom0=yes)” and reboot in 5 seconds. I tried to find out another kernel package with xen patched and non-PAE support, but found there is no such kind of thing…

Finally I found a bug report for Debian Kernel Team: another Pentium-M user complain about can’t install kernel package with xen. But the bug was tagged “won’t fix”… And the developer said that the xen patch was unstable when using with a non-pae support machine, and it was only appear in some of Pentium-M cores.

God….

UPDATE: I have installed xen from source successful, and everything goes well.