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

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“rcu_preempt detected stalls on CPUs / tasks” message appears to continue

My board continues to display the message below. The terminal does not have any input. What is it with the following message, which I know? (T, g, c, q ...) What is the cause of this phenomenon? ...
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48 views

Compiling a single kernel module which resides in the kernel tree

I have updated my Linux kernel to 4.3.3, everything works smooth except my webcam (QuickCam® Pro 9000) which is not working. According to the dmesg, the kernel recognizes the I have plugged a usb but ...
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27 views

How async_port_probe() call works in linux kernel?

To Understand the SATA device enumeration process I was studying the driver/ata/ata_piix.c which is showing as SATA host driver for my system in the output of lspci command. 00:1f.2 IDE interface: ...
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1answer
16 views

where is make_request_fn source code in linux kernel

in my study and examine linux kernel code I encountered with function make_request_fn. in this link it says that this function type definition is in include/linux/blkdev.h, line 211 : typedef void ...
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24 views

What is txqueuelen equivalent for receiving in linux?

I have always wondered that txqueuelen in output of ifconfig command defines transmission queue length in linux in terms of packets which I assume get utilized in various qdisc management while ...
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75 views

Linux Kernel module Remote Debugging with GDB + KGDB, Remote 'g' packet reply is too long

I am trying to remotely debug Linux Kernel and I am having issues. My setup: Target machine with Ubnutu Linux with my custom kernel 4.3 which I built with debugging information and KGDB. ...
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31 views

printk does not prints in terminal

I inserted some printk in kernel 3.15.1 functions such as theese: in fs/read_write.c in function read(): printk("Ata: Im in fs/read_write.c and in function read"); in same file in function ...
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52 views

Creation of the heap region/segment in Linux

It's my understanding that on Linux the process loader doesn't automatically create a "heap" region for a process like it's the case for the stack, is that correct? I used /proc/$$/maps and before ...
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What is a “subreaper” process?

The word "subreaper" is used in some answers. Searching Google also turn up entries where the word is "just used". How can I understand what a "subreaper" is?
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28 views

which section of kernel, manages io requests?

I know that the Block IO layer in Linux io stack manages and schedules io requests. but i do not know where is this code? indeed, i wanna see the section of code in kernel which corresponds to this ...
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69 views

In which thread does block driver issue commands to block device?

I'm currently reading "Understanding The Linux Kernel" book, as I've understood block I/O request order is like this; user space call => vfs call => I/O scheduler call => block device driver call. ...
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54 views

How to find the driver (module) associated with SATA device on Linux?

For one of my applications, I have to understand the the SATA device driver flow. As per my understanding, SATA device driver should be there in the Linux kernel tree. I have referred how to find the ...
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12 views

last samples are skipping when we do record and playback in loop back mode in linux

I am just connecting my output to the input of codec using mixer controls in linux. I am recording the data with tinycap in bag round and then I started playing of a 30 seconds sine tone using ...
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78 views

Linux 4.3 - Waiting for root device /dev/mmcblk0p1

I want to update my custom i.MX6 Board to Linux 4.3, but with the new Kernel the boot process stops at boot and can't load the rootfs from sd-card. With the old Kernel 4.1.x it works fine with the ...
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1answer
50 views

Porting Linux on LPC2148 board

Till now I was working with Raspberry pi, beaglebone etc. So, I am looking to do something new. So, I decide to port Linux on my LPC2148 board. But I am unable to find any tutorial regarding linux ...
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61 views

Create CentOS-7.1 custom iso with upgraded kernel-4.2.6

I am trying to create CentOS-7.1 custom iso with kernel-4.2.6. But I am facing issues while installation. Please see attached image for details. I have followed below steps to prepare custom iso ...
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26 views

Kernel module version enforcement

Linux can be configured to require that kernel modules be digitally signed. On kernels built for embedded devices and consumer devices (i.e., tablets, smartphones, etc.), I can still see that this ...
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how to build kernel-tools-4.2.xx.rpm and kernel-ltools-libs-4.2.xx.rpm

I am trying to upgrade Centos-7 kernel (kernel-3.10) to (Kernel-4.2.6) and for that I downloaded kernel from kernel.org and create rpm for the custom configuration (arch x86_64)using "make rpm". ...
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13 views

Linux tools for perf (install linux-tools-3.15.0)

I use Linaro version of Linux (Linaro 12.11) on my embedded target with ARM9 Core. For a certain profiling, I need to use the perf tool. perf require linux-tools-3.15.0 to be installed on my device. ...
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355 views

Intel Skylake + DisplayPort 1.2 MST/Daisy chain on Linux

I am planning to buy hardware for using DisplayPort 1.2's MST feature to daisy chain two monitors in combination with the Intel Core i5 6600 Skylake processor on Ubuntu. Is this supported yet with the ...
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1answer
34 views

DKMS modules never installed properly on kernel upgrade

I have multiple DKMS modules installed on my system, some of them mine, and some of them belonging to pretty major maintained packages such as Oracle's VirtualBox 5. What I've found is that on every ...
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61 views

Remapping Apple Keyboard with Linux Mint

I like to use an apple wireless keyboard with my laptop that runs Linux Mint 17.2 Cinnamon 2.6.13 64-bit with the 3.16.0-38-generic kernel. However, I would like to remap the fn, alt, command, control ...
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52 views

Running a real time kernel on Debian

As I have Debian 8 running on my laptop, I have got some questions about making my OS a Real-Time one: Does the Debian GNU/Linux distribution have an official Real-Time version? (I found that the OS ...
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66 views

Are there more advanced filesystem ACLs beyond traditional 'rwx' and POSIX ACL?

Are there any simple and integrated (i.e. embedded into filesystem) ACL patches for Linux kernel exist at all? The problem is simple: I need something more flexible and advanced beyond classic 'rwx' ...
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41 views

SIGSEGV: 0x0000000000000000 in ?? ()

I am executing an iperf connection between two UML machines running the following kernel: Linux client 4.1.0-ga61e56d #55 Mon Nov 30 13:51:59 CET 2015 x86_64 GNU/Linux I am working on the TCP/IP ...
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17 views

What can interrupt execution of threads which are pinned to cores?

I do low-latency application development and I use isocpu and set thread affinity to reduce (eliminate?) context switching during my critical threads. However, I am unsure what other types of ...
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15 views

How does an OS detect an access to random memory address of a compiled program? [duplicate]

I've read a couple things about memory management/virtual memory and I need a little more details on one important point. If I compile a program and it does an access to a hard-coded address without ...
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1answer
41 views

uninstalled kernel cannot boot anymore

So, basically I messed up I tried updating debian wheezy to debian jessie and at some point aptitude wanted to uninstall the kernel, I got a warning but I had faith and allowed it. now I only have an ...
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1answer
38 views

Why are there module options AND driver options - e.g. for the i915 module?

The i915 Kernel module has several "module options" like the infamous enable_rc6. However, for the xorg config file, there are further options such as TearFree. I was wondering - why are there two ...
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19 views

kernel address and completly reserve memory block

I want to reserve initial 512M of total 1G RAM(768 MB is mapped as LOW MEM and 128 for vmalloc) The kernel data and text is residing in the initial section of RAM (starting at 0xc0008000). how it is ...
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47 views

Why the oldest kernel is marked as recommended in Linux Mint?

In update manager, there is View->"Linux kernels" option. It contains a list of kernels and as far as I know the freshest builds must be the most optimized and stable. For example in Linux Mint 17 ...
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21 views

linux kernel development, file open sys call [duplicate]

I just started reading OS books and traversing through linux kernel code. I was trying to locate how the file open system call is implemented. I found its declartion in /linux/fs.h. But I am not able ...
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60 views

How to install kernel development headers to staging with BuildRoot?

I am planning to do some Rasperry Pi C/C++ kernel module development using BuildRoot 2015.08.1. What works: I can build a kernel and a rootfs and boot the Raspberry Pi. I can build/rebuild a "hello ...
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15 views

USB behavior changes when laptop is plugged

I have a USB camera (from IDS) and I wanted to plug it to my new laptop. I installed the software and everything was fine until all frames dropped. After an long investigation I finally understood ...
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30 views

sysfs alternative to /proc/acpi/button/lid/LID/state

As you probably know ACPI procfs is deprecated in new kernel versions and with sysfs I don't know of a clean way of reading the state of the lid button. The only way I've come up with is hooking up ...
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Why are slab objects not reclaimed automatically

Everyday after a full system backup, various programs are failing with read errors until I run echo 2 > /proc/sys/vm/drop_caches to free reclaimable slab objects. For example, here's the output of ...
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42 views

Upgrade Squeeze to Wheezy now no modules.dep

After upgrading Squeeze to Wheezy my server will no longer boot. I'm only able to boot, by selecting a previous kernel (2.6.32). linux:~# find /lib/modules/3.2.0-4-amd64/ -maxdepth 2 ...
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What is the minimal version of kernel on which ARM Slackware 14.0 will run?

I'm running Debian Lenny on a ARM NAS with 2.6.24 kernel. Debian in this version is missing many important security fixes and software patches, but when I've tried to run Debian Squeeze on the same ...
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2answers
20 views

Run script on startup for Old Linux kernel (3.0.0)

I need to run a script on system startup, but the Linux version is very old, so: There is no rc.local. Even when I created it and gave it a command, it was never run. There is no crontab at all. ...
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22 views

My RHELserver rebooting automatically I check the logs from boot logs

Server OS: uname -a Linux abc2.6.18-194.el5PAE #1 SMP Tue Mar 16 22:00:21 EDT 2010 i686 i686 i386 GNU/Linux # cat /etc/redhat-release Red Hat Enterprise Linux Server release 5.5 (Tikanga) ...
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97 views

Is there a way to temporarily disable segfault messages in dmesg?

Linux kernel keeps logging segfaults in ring buffer. a.out[25415]: segfault at 8049604 ip 08049604 sp bf88e3fc error 15 in a.out[8049000+1000] Is there a way to temporarily disable it? My usecase ...
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17 views

API for Kernel Module Development

I want to know if there is an API documentation listing all the functions/methods in the Header files? E.g. linux/kernel.h listing functions like printk(), linux/moduleparam.h indicating functions ...
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50 views

dd and USB - how does it work?

When you do: dd if=somefile of=/dev/sdX bs=1024 count =10 with a magnetic Hard Disk, and if the disk has say R/W multiple sector transfer: Max = 16 one can estimate that 16 * 512 = 8192 so setting a ...
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250 views

Why can't the kernel run init?

I've downloaded the Raspbian image on this page. I'm trying to compile a kernel that can be used to boot the image within qemu. I downloaded the Linux kernel source from kernel.org and ran: make ...
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12 views

Error in kernel recompilation

I have been trying to recompile the kernel in VirtualBox. But it resulted in an error make :*** [vmlinux] Error137. vmlinux is the name of my virtual machine. Printing kernel log gave [12560.424556] ...
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45 views

How to write a Patch for VyOS kernel

I am new to VyOS development. I have written a patch which will fetch info from the VyOS kernel module and write it on a netlink socket. But the problem is I am not sure if I should edit the kernel ...
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1answer
55 views

Centos 6.5 will not boot

The error below happens when booting up in to my distro of Centos 6.5. This happened after changing my paths in my fstab to UUID's. Server has two drives in RAID1 for the file system. I have access to ...
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1answer
116 views

How do I add CPU frequency governors to the Linux kernel?

CPU frequency scaling in Linux is by default performed via a governor, which as far as I know is included in the kernel. So far, on PC/server Linux kernels I've only seen the userspace, powersave, ...
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78 views

Linux/Embedded Linux - Understanding the Kernel and additional BSP specific components [closed]

*tldr; I would like to generally understand how the world of linux / embedded linux works. What do I need to do to take the Linux mainline and compile/deploy it on a board with different processors ...
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33 views

Microkernel (e.g. GNU Hurd) more secure than monolithic kernel (Linux)? [duplicate]

I would like to understand (in relatively layman's terms) if and how a microkernel such as the Mach-based GNU Hurd is more secure than a monolithic kernel such a Linux. Additionally, does a ...