Linux kernel compilation jots

Just a few notes to self as I compiled a kernel on a x86_64 machine, targeting an i386. Kind-of cross-compilation, but with no need for a cross compiler. Remember to update the (extra) version number in the Makefile. After copying a known config file to .config: $ make ARCH=i386 oldconfig $ time make ARCH=i386 -j [...]

Linux: Yet Another Google Chrome “Aw, snap” solved.

“Aw, snap” in Google Chrome happens when a process (or thread?) involved with Chrome dies unexpectedly. I got quite a few of those, and learned to live with them for about a year, as I couldn’t figure out what caused them. It was clear that it had to do with Adobe Flash somehow, and that [...]

Playing with Linux namespaces

Intro Linux namespaces is the foundation for container-based virtualization, which is becoming increasingly popular. Aside from the ability to isolate a shell (and the processes it generates) from the “main environment”, as is required for this kind of lightweight virtualization, namespaces is useful for overriding selected functionalities. So I’m jotting down things I use myself. [...]

iowrite32(), writel() and memory barriers taken apart

Introduction Needing to remove superfluous memory barriers from a Linux kernel device driver, I wondered what they actually do. The issue is discussed down to painful detail in Documentation/memory-barriers.txt, but somehow it’s quite difficult to figure out if they’re really needed and where. Most drivers rely on subsequent iowrite32′s (or writel’s) to arrive to the [...]

SOLVED: Lenovo Yoga 2 13″ with “hardware-disabled” Wifi

Overview Having a Lenovo Yoga 2 13″ (non-pro) running Ubuntu 14.04.1, I couldn’t get Wireless LAN up and running, as the WLAN NIC appeared to be “hardware locked”. This is the summary of how I solved this issue. If you’re not interested in the gory details, you may jump right to bottom, where I offer [...]

i.MX: SDMA not working? Strange things happen? Maybe it’s all about power management.

I ran into a weird problem while attempting to enable SDMA for UARTs on an i.MX53 processor running Freescale’s Linux kernel: To begin with, the UART would only transmit 48 bytes, which is probably a result of only one watermark event arriving (the initial kickoff filled the UART’s FIFO with 32 bytes, and then [...]

Wine: Picasa failed to start Fedora 12 after a kernel upgrade

I upgraded my kernel from 2.6.35 to 3.12, and Picasa 2.7 failed to start. Instead of starting, tons of winedbg processes were created at a rapid speed. If I didn’t kill everything related to Picasa within a minute or so (that is, all winedbg processes and any process having “picasa” in the string of “ps [...]

Automatic mount stops after kernel upgrade and sysfs

I really have this thing about backward compatibility, which is why I chose to enable the CONFIG_SYSFS_DEPRECATED and CONFIG_SYSFS_DEPRECATED_V2 kernel flags when compiling kernel 3.12 for Fedora 12. After all, an old distribution with a new kernel. This turned out to be wrong: The distribution isn’t all that old, and automounting stopped to work for [...]

VMware Player or Workstation: Patching for Linux kernel 3.12 (or so)

For a reason not so clear to me, VMware doesn’t keep its drivers up to date with newer kernels, so they fail to compile against newer kernels. Consequently, there’s an insane race to patch them up. It starts with a compilation failure at the GUI level, and sooner or later it becomes clear that there’s [...]

Kernel compilation without extra “+” or other markers in the version string

So there’s this “+” sign added to the kernel version (as displayed with uname -r) when the kernel is compiled with a git tree that doesn’t sit on an official version (or more precisely, not on an annotated tag). Which kinda makes sense to tell the kernel’s users that the kernel isn’t exactly the vanilla [...]