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Questions tagged [linux-kernel]

Questions about Linux kernel and Linux kernel related topics eg. implementation details such as system calls, kernel customization, etc. For Linux user space topics which do not involve kernel details, [linux] or distribution tag are more suitable.

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NVMe PCIe disk power cycling

I want to test an NVMe SSD that is connected to a PCIe slot of my motherboard. The test procedure is a specific algorithm that writes workloads to the SSD, while the SSD is exposed to radiation (e.g., ...
mamahuhu's user avatar
  • 243
11 votes
0 answers
2k views

What network connections are not seen by netstat/lsof/ss?

Network monitoring tools ss, lsof -i, netstat -ltupw and similar have limitations like namespace and thus they don't show the whole machine connections. (for namespace created with ip we can see other ...
intika's user avatar
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9 votes
1 answer
5k views

Linux 3.x fails assigning PCI BAR memory

I got an IBM x3850 type 8864 machine, I can successfully boot using a 2.6.32 kernel but when I try to use a 3.10 kernel or newer the kernel fails to initialize all PCI slots (I can fix this (manually),...
Jan's user avatar
  • 91
8 votes
0 answers
2k 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 ...
Mark Raymond's user avatar
7 votes
0 answers
2k views

How to read the output of the show-memory-usage SysRq?

I couldn’t find any (recent) documentation on reading the output of the show-memory-usage SysRq (Alt+SysRq+m). So what can one learn from looking at it? Here is an example output form my box (Kernel ...
kirelagin's user avatar
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6 votes
0 answers
174 views

Kernel config for keyboard special LEDs

I'm building a 4.9 linux kernel (which is working great) for my T460s. The F1 key has a led that shows if sound is muted. I can't get this LED to work even when enabling all kinds of LED-relevant ...
Jan's user avatar
  • 7,782
6 votes
0 answers
373 views

Kernel config diffs - better way to maintain

I maintain one Linux distro (LEAF) with multiple kernel targets, so it needs to have multiple kernel configs (one reference config + usual patch files for other targets). But this adds headache on ...
NiTr0 N's user avatar
  • 61
6 votes
1 answer
1k views

What does "make install" do in the Makefile that comes with the kernel?

I'm trying to identify what does make install do with the kernel and what does the actual "install" of the kernel once it's been compiled means. The problem is I can't really identify the target (...
TheMeaningfulEngineer's user avatar
5 votes
0 answers
5k views

NFS Cannot allocate memory

The other night I was trying to restart NFS services but then I received the following error messages: kernel: [81818.428785] nfsd: unable to allocate nfsd_file_hashtbl rpc.nfsd[15567]: error starting ...
Natalie Adams's user avatar
5 votes
1 answer
2k views

How does one disable an option enabled by default in Kconfig?

Let's say I have an option: config SETTING_WITH_DEFAULT bool "Some setting which defaults to y" default y I want to make an option which would deselect this default: config ...
Paul Stelian's user avatar
5 votes
0 answers
1k views

How does linux decide the load address and entry point when execve an ELF?

When linux execve() an ELF, it will mmap that ELF into the process's memory space and start to run code from the entry point. But how does the kernel decide the load address and entry point of the ELF?...
炸鱼薯条德里克's user avatar
5 votes
1 answer
2k views

How to check if If i2c-hid and hid-rmi are not used for touchpad?

I'm seeing the following warning in dmesg: [ 2.631179] psmouse serio2: synaptics: Your touchpad (PNP: SYN1218 PNP0f13) says it can support a different bus. If i2c-hid and hid-rmi are not used, you ...
Tim's user avatar
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5 votes
0 answers
4k views

Kernel compiling - Error during sync of the configuration

I am trying to compile the 4.19 kernel on my Linux Mint machine. I copied my current config (which is from 4.15), opened make menuconfig in order to append a local version string, saved it and then ...
Raven's user avatar
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5 votes
0 answers
1k views

CPU high load native_queued_spin_lock

I'm using Debian 9(stretch edition) kernel 4.9., hp dl385 g7 server with 32 cpu cores. NIC queues are tied to processor cores. Server is shaping traffic (iproute2 and htb discipline + skbinfo + ipset +...
Sergey K.'s user avatar
5 votes
1 answer
2k views

How can I detect whether an "NMI watchdog: BUG: soft lockup" is a hardware or a software issue?

Soft Lockup dmesg reports in my laptop, since quite some time now, NMI watchdog: BUG: soft lockup every time I try to use updatedb or firefox. Samples of what is reported posted at https://github.com/...
Nikos Alexandris's user avatar
5 votes
0 answers
2k views

Can't run any snap using linux 4.12 : snap-confine has elevated permissions and is not confined but should be

I am using Ubuntu 17.04 with linux kernel 4.12.2 which I installed using the software ukuu (Ubuntu Update Kernel Utility). Every time I try to run a snap in my system when I am using this linux ...
Sidahmed's user avatar
  • 1,348
5 votes
1 answer
2k views

Getting big endian linux build to boot on ARM with u-boot

I’m trying to make a big endian build of a linux distribution for ARM. Since I’m on Gentoo, cross-compiling couldn’t be easier. I’ve already built it all, but then got stuck with getting it/the kernel ...
xHire's user avatar
  • 51
5 votes
1 answer
3k 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 being the cause, ...
ManuelSchneid3r's user avatar
5 votes
2 answers
1k views

Problem when trying to cross-compile an ethernet driver on an old Linux kernel

I'm currently trying to cross-compile a network driver against an old Linux kernel, in version 2.6.27.7 but the compilation fails and prints: make[1]: entering directory « /home/johann/Desktop/linux-...
blablabla's user avatar
5 votes
0 answers
2k views

When would I use FBDEV vs DRM vs DSS?

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 one versus the other?
tony19's user avatar
  • 151
5 votes
1 answer
1k views

How are Linux kernel bugs being tracked?

What an hour of Googling bring out that mainstream Linux kernel bugs are being logged in two distinct systems: Mailing list This is the Linux kernel development discussion and bug reporting ...
sherlock's user avatar
  • 646
4 votes
0 answers
119 views

Linux reuse of ports after TCP RST

I have a set up where I do a lot of HTTPS connections to customers, and under high load some connections time out. After digging a bit I found that it happens when we or the server (same behavior in ...
Zmegolaz's user avatar
4 votes
0 answers
653 views

How does anti-cheat work and how is it distributed on Steam Games?

According to Levvvel's list of kernel-level anti-cheat games, many modern games use kernel-level anti cheat. One provider of kernel-level anti-cheat is Epic with Easy Anti-Cheat and one game using ...
Evan Carroll's user avatar
  • 31.8k
4 votes
0 answers
735 views

/proc/diskstats disk time spent writing more than 1000ms*CPU-core-count per second

I'm interested in how could one interpret the results of procfs-diskstats. It looks like an API, but I see no exhaustive explanation in Internet or man pages or Linux kernel Documentation. There is a ...
z0lupka's user avatar
  • 285
4 votes
1 answer
1k views

How to debug Linux kernel with JTAG + GDB?

I've successfully established a JTAG connection and serial port connection to my development board. I've followed the below diagram (with a little bit of difference). my GDB_client is on my Linux host ...
Mahyar Shokraeian's user avatar
4 votes
0 answers
530 views

Linux kernel cannot execute any binary (error -12)

Problem: Memory Allocation Problem my platform: SOC = STM32H743 (ARMv7E-M | Cortex-M7) Board = Waveshare CoreH7XXI Linux Kernel = 5.8.10 (stable 2020-09-17) initial defconfig file = stm32_defconfig ...
Mahyar Shokraeian's user avatar
4 votes
0 answers
1k views

QEMU kernel for raspberry pi 3 with networking and virtio support

I used the QEMU(qemu-system-aarch64 -M raspi3) for emulating the Raspberry pi3 with the kernel from the working image. Everything was working but there was no networking. qemu-system-aarch64 \ -...
zeropoint's user avatar
4 votes
1 answer
508 views

Kernel Panic not showing up?

I'm writing a kernel module and I was hoping to get the beautiful Kernel Panic screen with all the details when I call panic(), but my machine just freezes without displaying anything. I know kpanic ...
CAGYL's user avatar
  • 41
4 votes
0 answers
388 views

udev rule not worknig as expected with PROGRAM key

My system is Debian Buster with Kernel 4.19. I have a simple udev rule as below that was working fine with Debian Jessie. Now same rule seems to be not working in newer distribution. KERNEL=="sd[a-z]...
user3591654's user avatar
4 votes
0 answers
2k views

Is there any tool to generate kernel .config file?

I watched a clip on customizing kernel, rebuilding, installing, etc. where the gentleman suggested to use an existing .config file with make menuconfig or make xconfig. I wanted to use one that comes ...
user avatar
4 votes
0 answers
1k views

overall HIGH CPU utilization, but top is not showing process which is contributing to that spike

Below is the output of a top command, which is showing "57.6%us, 24.0%sy" overall cpu utilization at a particular moment, but there is no process which is contributing to this spike of cpu usage. ...
Harsha's user avatar
  • 41
4 votes
0 answers
774 views

How to additional public keys to .secondary_trusted_keys?

I am trying to add additional keys to .secondary_trusted_keys. Documentation says, to do so the additional keys has to be signed by a key which is already a resident in either .builtin_trusted_keys or ...
Prashant's user avatar
4 votes
5 answers
17k views

Kernel cannot find init in initramfs image

I'm trying to get my embedded system to run an initramfs. Right now 'init' in this initramfs does nothing but echo a message to test if it is being ran. My init script: #!/bin/sh echo "HELLO ...
dangeroushobo's user avatar
4 votes
0 answers
795 views

Time measurment in Linux kernel: how are clock_gettime, gettimeofday and getrusage related?

I am trying to understand how time is measured by the Linux kernel. I tried to go through the kernel code, but I miss the big picture to understand the code that I'm reading, even if this article ...
Vincent's user avatar
  • 171
4 votes
1 answer
4k views

Controlling USB-C Power Delivery on a HP ProBook G5 laptop

Question: I want to look at parameters under /sys/class/typec, but on my laptop, this doesn't show up. When I load the typec module manually, the directory appears but it is empty. After loading tcpm ...
matejcik's user avatar
  • 141
4 votes
0 answers
66 views

Which Linux kernels include a particular bug fix?

How do I know which Linux kernels have merged a particular bug fix? For example, as mentioned in this question: Kernel Bug 198357 - iwlwifi: failed to remove key (1, ff:ff:ff:ff:ff:ff) from hardware ...
Tom Hale's user avatar
  • 31.2k
4 votes
0 answers
194 views

What is the modern way to develop a Linux auditing kernel module?

I'm new to Linux Kernel development, and I am now assigned a task to develop a Linux kernel module, which can monitor the network, filesystem, USB and serial ports. I am aware of the things like ...
haohaolee's user avatar
  • 141
4 votes
1 answer
3k views

Finding which specific Python process was killed by Linux OOM killer

I'm trying to figure out which specific Python process or executable was killed by the Linux OOM killer. In /var/log/messages I get this: Aug 18 03:19:11 169 kernel: [ 7747] 0 7748 3226957 ...
jersey bean's user avatar
4 votes
0 answers
2k views

Prevent a plus sign from being appended to Linux build

The kernel build system like to append + to the kernel's local version string whenever it detects that the source tree is version controlled with Git. I can prevent this annoying modification to ...
Melab's user avatar
  • 4,148
4 votes
0 answers
3k views

Limit on number of virtual interfaces in linux?

I am running some automated tests with docker containers, and this includes creating a lot of veth interfaces (about 2 per container, ~1000 containers). Whenever I do this, the system shuts down. ...
devil0150's user avatar
  • 681
4 votes
1 answer
3k views

How do I extract vmlinux from an ARM image?

I am trying to extract vmlinux from Ubuntu's netboot kernel used in the armhf architecture. The script extract-vmlinux returns extract-vmlinux: Cannot find vmlinux. It even fails when I try to use ...
Melab's user avatar
  • 4,148
4 votes
0 answers
2k views

Dell XPS 13 9350 wifi dying with Broadcom BCM4350 and 4.8 kernel

Launchpad report: for all those with the same problem, please subscribe to this report I opened in Launchpad so that it can gain some traction. I've been using Ubuntu 16.04 with kernel 4.7 for some ...
Leo Brito's user avatar
  • 173
4 votes
1 answer
212 views

Are devices with kernels below 3.6 vulnerable to CVE-2016-5696?

Today I was reading about the potential impact of CVE-2016-5696 in Android phones running Linux 3.6+ and though my phone has 3.4 I checked the value of net.ipv4.tcp_challenge_ack_limit and it is also ...
user2859982's user avatar
4 votes
1 answer
6k views

using cpu.cfs_quota_us and cpu.cfs_period_us to limit CPU usage

There are 32 cores in a system (2 cpus each 16 cores) and I want to limit a user to use only 4 cores (100% usage for that 4 cores). There are two kernel parameter for that according to the manuals: ...
mahmood's user avatar
  • 1,241
4 votes
2 answers
7k views

How to dump the dmesg AKA Kernel logs to a single .txt file from the kernel boot?

I am trying to understand the SATA Host-Device Communication and for that I have put a lot of debug messages in the kernel driver code. Now messages are in such a huge amount that I am not able to see ...
Hemant's user avatar
  • 113
4 votes
0 answers
2k views

Print kernel memory layout

Userland memory layout can be inspected by looking into /proc/self/maps. I am wondering if there is a similar facility allowing to inspect runtime kernel memory layout?
Richard's user avatar
  • 879
4 votes
0 answers
2k views

Centos 7 boot up with custom kernel problem

I have installed centos 7 on virtualbox machine which has kernel-3.10.0-123.20.1.el7.x86_64. I am trying to build Linux kernel from kernel sources. I downloaded the kernel source files from: http://...
nyzsirt's user avatar
  • 41
4 votes
1 answer
3k views

Corrupt LVM metadata header after kernel update

I'm running Debian Wheezy (Linux wheezy3.2.0-4-amd64 #1 SMP Debian 3.2.63-2+deb7u1 x86_64 GNU/Linux) as an encrypted LVM with hardware raid 1 (Adaptec 6405E) on a supermicro server. I was encounting ...
heuri's user avatar
  • 113
4 votes
0 answers
2k views

update kernel without restart

Recently Linux got a new feature called Live Kernel Patching, which you means you don't have to restart your system to update kernel. Is there any other kernel which has this feature already or Linux ...
Alex Jones's user avatar
  • 6,383
4 votes
1 answer
429 views

kernel: nf_conntrack: table full, dropping packet; Underlying Reason

I have a modified linux on an ARM9 processor. It was working OK, but yesterday I got this error repeatedly: kernel: nf_conntrack: table full, dropping packet I have 2 questions: How can I find out ...
Aman's user avatar
  • 211

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