The kernel of operating systems popularly known as Linux, or sometimes GNU/Linux.

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186 views

EDID Invalid on USB DisplayLink Device

I have a Sabrent USB to HDMI adapter which is a DisplayLink device. It's recognized by udl as being a DisplayLink device, yet seems to be rejected/disabled due to having an invalid EDID: ...
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26 views

Why does a device show up as hidraw instead of hiddev?

I read the kernel documentation for hidraw and hiddev, and I understand the differences, but I am wondering how the kernel decides whether or not a device should show up as /dev/hidraw* or ...
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310 views

When do I need to specify add_efi_memmap as kernel argument in UEFI/EFI boot?

I am reading some tutorials how to EFI stub (efistub) load the Linux kernel. These instructions often use kernel boot parameter add_efi_memmap. The intended hardware is Intel x64 having 8GB of RAM. My ...
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97 views

Why are block sizes limited by page size in Linux?

In many (all?) file systems that Linux uses, including ext2/3/4, the maximum block size is the page size of the architecture Linux is running on, ie. 4KiB on x86. Why is there this limit? Might this ...
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2k views

Cannot use dual monitors in Elementary OS Luna - radeon driver

Once I attach the external monitor, the image on both monitors is activated but is messed up, just chaotic lines and colors, so that i cannot access the 'Displays' settings. This never happened with ...
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2k views

“Northbridge Error (node 0): ECC Error in the Probe Filter directory”

I've received an e-mail from a user worried that the following errors on one of his servers is indicative of a serious problem. The trouble is, the errors below are all that I have to go on. I ...
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202 views

How to set CONFIG_PREEMPT_NONE in RHEL 6.4 (linux)

I am trying to tune the RHEL6.4 Kernel to handle server style load for of my application. With RHEL 6 scheduler has been changed to CFS and with RHEL 5 my application works fine. I would like change ...
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251 views

My SMDK2416 (for s3c2416) kernel works on 64MRAM but crashed on 128M

I'm currently working on embedded arm linux with smdk2416(s3c2416) The kernel is working on the 64MRAM. Recently, I need to increase the RAM from 64M to 128MB with 64MB on bank0 and 64MB on bank1. ...
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612 views

How extended (4MB) and regular (4KB) paging coexist?

On x86 architecture, "Extended paging" allows page frames (physical memory) to be 4 MB instead of 4 KB. The book "Understanding the Linux Kernel, 3rd" at chapter 2 "Memory Addressing", sub-chapter ...
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235 views

When would I use FBDEV vs DRM vs DSS?

I'm new to Linux graphics, and I'm interested in developing a graphics driver. I see that Linux supports three methods for writing graphics to the display device FBDEV DRM DSS2 When would I use ...
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27 views

“can't write to batman adv kernel file” while using “batctl p mac-address”

I installed batman-adv and batctl on Ubuntu 14.04.1. When I issue the comand: batctl p 00:16:bf:01:68:46 I get this error: Error - can't write to batman adv kernel file ...
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65 views

What is the minimum round robin scheduing interval supported by Linux?

For some reason, I want to have 10 processes share the same CPU core by affinity. As you know, to achieve CPU sharing between processes, we can exploit the Linux round robin (RR) scheduling policy. ...
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19 views

Possibile sources of 5us-20us latency gap when sending long block of of serial data to tty device?

I have a trivial C program that just sends a large block of data out the serial port at a fast baud rate. When looking at the bits actually coming out of the port, I see that there is a almost always ...
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36 views

Is a page with “PROT_NONE bit set” eligible for swapping?

From the following link: Page Table Management - kernel.org, I understood that the bits PROT_NONE and PRESENT can be used to let the OS know that a page is protected but is resident in memory. I am ...
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60 views

How does the kernel store the virtual memory area?

I am trying to understand do_page_fault in fault.c (x86 architecture). I came across the method access_error where we compare the error code to the vm flags. As per my understanding, we are checking ...
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82 views

Virtual kernel memory layout in dmesg linux kernel 2.6.31

I'm working on a embedded linux project for ARM architecture, kernel version is 2.6.31.12-rt21. In dmesg, I cannot see the virtual kernel memory layout like this: virtual kernel memory layout: ...
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288 views

Server won't boot, kernel panic - not syncing

After a reboot of a CentOS 6.2 server we are getting a kernel panic with the following error: Kernel panic - not syncing: Attempted to kill init! Panic occurred, switching back to text console ...
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122 views

kdump doesn't produce core dump after buggy module is loaded

I am running kernel 3.14.4 on Fedora 18. I am experimenting with a kernel module I am making. The module has a bug (at least one) and crashes the kernel. Sometimes I see a stack trace on my frozen ...
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131 views

How to interpret cpu_idle and cpu_frequency event's trace logged by ftrace?

I used ftrace to trace two events, cpu_frequency and cpu_idle. I am not able to find out any documentation which states how to interpret this information. I have provided two snippets from the ...
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91 views

Set up OS and Runnig app using x32-ABI

Intro I just moved to a 64bit installation and I'm experiencing big difference in memory usage ( especially for app like chrome, firefox, mysql and java apps ): - While before 4gb were enough now they ...
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68 views

Why does the kernel boot faster with less memory allocated?

This is not a important question, I'm just curious. Something strange happened, which isn't quiet clear to me: In the kernel command line, the amount of the memory can be set statically with the ...
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55 views

Detach keyboard from the kernel

I am writing a remote controller app for an octocopter and want to use a keyboard as an input device for this app but I don't want it to have any effect outside this app. Somehow I would like to make ...
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111 views

How can I automatically include all firmware needed by selected Linux kernel modules

I have certain modules which I need compiled into the kernel. Some of these modules require firmware, which used to be automatically included from /usr/src/linux/firmware/. However, no new firmware ...
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55 views

Linux kernel API changes/additions

I'm trying to find a webpage or docs or XYZ that will allow me to see all the API changes/additions/removals between two kernel versions. I found http://kernelnewbies.org/LinuxChanges, but I'm not ...
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248 views

how to stop kernel threads preempting real time user space processes?

I created some processes in user space and tried to visualize its working in kernelshark with the trace recorded using trace-cmd. But kernel processes like the ones shown below are preempting my ...
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165 views

What changed between kernels 3.7 and 3.9 that affects LVM/RAID root file systems?

I'm trying to fix a (very messy) system that the user hosed by running a kernel upgrade from 3.7.10 to 3.9.6. the root file system is on an LVM volume on top of a software RAID array. The boot manager ...
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734 views

Unable to install the selected kernel

I have problem with my DVD drive. It's corrupted and when I'm trying to install Ubuntu it stucks (even with the miniISO) I was able to successfully start the OS from system rescue CD. I'd like to ...
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225 views

Update jiffies value after waking up from suspend

The global variable jiffies holds the number of ticks that have occurred since the system booted. On boot, the kernel initializes the variable to zero, and it is incremented by one during each timer ...
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56 views

kgdb not returning control to gdb

I've compiled a kernel with kgdb support and I'm trying to debug it. I have two machines running, a debug machine (running the kgdb kernel) and the machine I'm using to debug it. They are connected ...
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3k views

mounting udev on /dev failed: No such device

I am trying to compile Linux kernel 3.2.36 with its source code on the x86_64 architecture. I followed the following set of commands under my Linux source distribution directory: make defconfig ...
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373 views

Error cross compiling linux kernel using buildroot

I am trying to build a kernel bt in cross compiling the kernel when I ran following command make CROSS_COMPILE=i686-linux- ARCH=x86 I got the following error: UCLIB_EXTRA_CFLAGS="" \ ...
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91 views

How to deal with closed source modules when configuring a new kernel build

I found this command very useful: make localmodconfig However, having some closed source drivers/modules ends up being a problem because this command can't find an appropriate way of including the ...
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383 views

Kernel 3.0.0-1 and NVIDIA driver boot problems

I can't boot kernel 3.0.0-1 on Asus G53S running Debian, it freezes when booting with: NVRM loading NVIDIA Unix x86_64 kernel module 275.28 then it times out with: udevd[350]: timeout: killing ...
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19 views

Is there support for flattened device tree in Sparc 32 port of the Linux kernel?

We are trying to write a minimal bootloader for booting the linux kernel on a Sparc V8 processor simulator. From what I understand, the interface between the bootloader and kernel consists of a data ...
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14 views

ifup wlan0 causes kernel Oops

on my laptop, when I do ifup wlan0, sometimes I get following call trace in dmesg. Other times, the log looks perfectly normal, and there are no kernel Oops messages. In both cases (with errors and ...
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25 views

GFP mask of 0x200da on a 64-bit system?

Recently, an OOM showed a GFP mask of 0x200da on a 64-bit system. How is that possible? 0xa would suggest we are talking about Movable Highmem, see: ...
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16 views

Weird X11 behaviour after resume from suspend

I experience the following problem with xfig, but I don't believe that it is a xfig problem: In xfig, I draw a text and then I can move it around with the mouse (after going into move-mode). As I ...
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44 views

How to create the framebuffer file node?

I'm working with a limited embedded device - Linux environment - that uses a custom DirectFB implementation to draw a user interface in its video output. I would like to exchange this method by a raw ...
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36 views

How to make 'install USB' with custom Linux?

I built my own custom kernel for new hardware.(Not a normal PC, embedded x86 device), and using syslinux I could create a booting USB for that kernel. After a few trial and errors, I was able to ...
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217 views

DisplayPort and Intel HD cause GPU hangs

My system has problems with the displayport connection. This is indicated by several problems that, at the first glance, do not have anything in common. The reason why I claim DP for beeing the cause, ...
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58 views

What are the two head.S files in linux source ?

In the linux source there are two different head.S files located at: arch/arm/kernel/head.S arch/arm/boot/compressed/head.S What is the puprpose of each one and what is the order of there execution ...
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77 views

Adding IPVS to the kernel

I am trying to setup keepalived on a pair of VPS load balancer servers. I have hit the road block of IPVS not being included with the kernal. IPVS: Can't initialize ipvs: Protocol not available I ...
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105 views

Disable kernel logging during initialization

I'm using a Linux image generated with buildroot for an embedded system. I recently disabled some modules from being generated with the image and now some logging messages are being shown during the ...
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206 views

Some questions compiling linux kernel with make-kpkg

I'm doing my first steps compiling the linux kernel and adding a new system call. I've managed to do it, but I still have some questions. For this task, I has set up a Virtual Machine guesting debian ...
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295 views

About Linux Memory Compaction (CONFIG_COMPACTION)

I have a question regarding memory compaction on Linux. Generally compaction is triggered when system cannot satisfy a large contiguous memory allocation. This causes the compaction to run on all ...
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266 views

CDC ACM doesn't working in a custom linux kernel

I've a cubieboard2 running arch linux with a custom linux kernel. In the cubieboard2 I plugged in my usb-serial device (like an arduino), the device is recognized as CDC ACM. My linux kernel has the ...
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92 views

Interfacing ds1337 RTC on LPC17xx

I am a newbie and I am trying to understand how to interface DS1337(RTC) on LPC17xx Board. This board uses uclinux 2.6.33. .CONFIG: CONFIG_RTC_LIB=y CONFIG_RTC_CLASS=y CONFIG_RTC_HCTOSYS=y ...
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119 views

Looking for a list of modules that are used during boot sequence

I'd like to use deferred init calls. This function allows to load modules in userland, that should actually be loaded during the boot sequence. Just for testing I'd like to modularize as many entries ...
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149 views

How to cause memory fragmentation on a Linux based embedded device?

Hardware ARM What am I trying to do: Answer: I am trying to create memory fragmentation on a Linux 2.6.31 based swapless embedded device. Why: Answer:I am trying to port some patches to Linux ...
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47 views

What are the linux kernel versions incompatibilities with btrfs?

I read that usage of a btrfs volume with a newer kernel can render it unreadable when that same volume is used with an older kernel. I have a mobile storage device that will be used by different linux ...