Everything about UNIX kernels: development, configuration, compilation, design, etc.

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3
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0answers
18 views

Confused result from counting page fault in linux [migrated]

I was writing programs to count the time of page faults in a linux system. More precisely, the time kernel execute the function __do_page_fault. And somehow I wrote two global variables, named ...
0
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0answers
9 views

Syslog message “rt_bind_peer(0) @ffffffffa0283f57”, twice in every second

My /var/log/syslog on a Debian server is flooded with lines similar to: Dec 23 16:05:40 server1 kernel: [ 686.957585] rt_bind_peer(0) @ffffffffa0283f57 These messages occur up to twice a second ...
0
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1answer
15 views

Does iptables protect from kernel vulnerabilities? [on hold]

I read a lot of kernel vulnerabilities which are beyond my understanding. I would like to reduce the risk of an issue related to one. If I block everything other than SSH on a server, will this help ...
-1
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1answer
32 views

Is the kernel version fixed within the life of a release/version of each Linux distribution?

I read the Table of versions of List of Ubuntu releases. I found that the kernel version for each release is fixed. E.g. the kernel is 2.6.24 for Ubuntu 8.04, 2.6.32 for 10.04, 3.2+ for 12.04, and ...
0
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0answers
16 views

add another field to user_struct [migrated]

I want to add new field ( to store number of ready process of this user ) to user_struct in file linux-source/kernel/user.c struct user_struct { atomic_t ready_processes; /* I add this field */ ...
2
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2answers
44 views

Why is userspace slower than the kernel?

I've heard that FUSE-based filesystems are notoriously slow because they are implemented in a userspace program. What is it about userspace that is slower than the kernel?
4
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1answer
36 views

what's the difference between page cache and buffer cache?

In linux OS, you can type command "echo 3 > /proc/sys/vm/drop_cache" to release memory, and you can type command "sync" to release the memory. And in linux kernel there are two kind of cache, one is ...
0
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1answer
19 views

Custom Kernel to Disable SATA and USB Devices

I am setting up diskless clients that will run on an internal network. I have disabled SATA and USB ports using a BIOS locked with a password, but this is easy to get around by using the jumper to ...
1
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2answers
47 views

Is system call the only way that a user program can intentionally affect the state of a Linux kernel?

I think there are several ways that a user program can intentionally affect the state of a Linux kernel. By invoking a system call; By invoking mmap() and writing the memory that has been mapped to ...
2
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0answers
53 views

Can the hard drive timeout be disabled in Linux (attempting task abort)

Unfortunately, when a hard drive (usually a virtual drive) is slow, Linux aborts requests to that drive after a timeout, possibly causing data corruption. Last time this happened to me, I had 2 vms ...
0
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0answers
10 views

Looking for c-state syscalls (Kernel 3.10 [migrated]

Where can I find Linux Kernel 3.10 syscalls to manage C-State CPU Power Management?
6
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1answer
152 views

Some basic questions about Linux kernel's security [closed]

I don't know much about Linux kernel, and I have some questions. What is the main purpose of separating kernel memory from user-space memory? To make sure that a user application cannot do anything ...
0
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0answers
22 views

different ways how Linux TCP/IP stack terminates connection

I have a Linux machine which connects to SSH server with SSH client(OpenSSH_4.1p1). SSH client machine has IP address 10.10.11.1 and SSH server has IP address 10.10.10.1. SSH client has kernel version ...
1
vote
1answer
27 views

take the DRAM performance of the processes into consideration when scheduling

The CFS scheduler in Linux schedules the processes based on the virtual runtime of CPU. But, the DRAM memory is the bottleneck in most of the emerging domains. Why not take the DRAM performance of ...
0
votes
1answer
25 views

Disallow change of init kernel parameter

is there any way to disallow changing init parameter on boot time? I want to prevent situation when someone reboot my server, edit grub entry and get access without password. Maybe some kernel ...
1
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0answers
5 views

Is inode_readahead_blks independent of read_ahead_kb?

I've been reading through the kernel documentation for block device sysfs tunables and I ran across the description for read_ahead_kb: Maximum number of kilobytes to read-ahead for filesystems on ...
0
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2answers
34 views

When building a new kernel in OpenBSD 5.6, can the name of `config` be something else?

I am using the release version of OpenBSD 5.6 and have to apply a patch called 004_kernexec.patch.sig (URL: http://ftp.openbsd.org/pub/OpenBSD/patches/5.6/common/004_kernexec.patch.sig ) An excerpt ...
2
votes
1answer
16 views

does the second kernel need kexec enabled

It's clear that you need the kexec syscalls in the 'first' kernel. But does the kernel that should get loaded (with kexec_load and reboot) need to be compiled with kexec? If yes, what extra code ...
0
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0answers
13 views

linux vlan bridge feature backport to 2.6 kernels

The VLAN-aware bridge was introduced to the Linux mainline on the 3.x kernels, according to this article on lwn: VLAN filtering/VLAN aware bridge Has this feature been backported to the 2.x kernels ...
0
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0answers
10 views

3.10.17 Kernel i2c buses missing on embeded system

On my ARM embeded system I have 4 i2c buses and only one shows up in /dev and in /sys/device/... folders. Other 3 i2c buses are not loaded. There is also no warning message inside dmesg, but there is ...
0
votes
1answer
27 views

BUG: scheduling while atomic

I have just installed Linux (OpenSUSE), and when start the OS, I get an error BUG: scheduling while atomic: systemd_udevd plymounthd... what does it mean?
0
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0answers
16 views

Suspend Crash in android 4.4

During suspend clocks are not turning off, meanwhile when we resume clocks are not getting turning on. I am getting crash like <4>[ 216.945252] WARNING: at ...
3
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2answers
405 views

What does LTR kernel mean?

I was reading some sites and came across (LTR) by the number of kernel. Can somebody explain what is means?
0
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1answer
85 views

Cannot boot latest kernel update after installing on new system

I recently built my own computer, and I was excited to finally get to the installation of the operating system. I chose Fedora 20 to use as my primary operating system, and I was able to successfully ...
0
votes
1answer
29 views

cc1: warnings being treated as errors when compile FreeBSD 8.2 Release

I am trying to compile FreeBsd 8.2 RELEASE kernel # uname -a FreeBSD 8.2-RELEASE FreeBSD 8.2-RELEASE #2: Sun May 18 00:07:10 PDT 2014 Build the kernel # pwd /usr/src # make buildkernel ... it ...
0
votes
1answer
43 views

Is hardware helping reducing crashes of OS X? [closed]

I am taking an OS course this semester, and we mentioned that device drivers can cause about 85% of crashes(for Windows). My understanding is that: since many personal computers are configured with a ...
0
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0answers
45 views

CPU load and power management (frequency)

question background In my understanding the load value (shown e.g. by top) allows (together with the knowledge how many CPU cores the system has) a very quick assessment which share of the ...
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0answers
39 views

loading ath9k_htc kernel driver fails

could someone please point me in the right direction to get my external wireless stick (TL-WN722N) working on my Xperia Neo (haida) smartphone? So far I've done the following: I downloaded ...
0
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0answers
34 views

Debian Squeeze: TCP/ICMP stops working suddenly (R8169 Driver)

we suddenly see our NETWORKING stops (TCP/UDP/ICMP) in our client system. tcp: We tried reaching our server every 5 seconds.But , there was no connection establishment TCPDUMP REF: ...
1
vote
1answer
30 views

Error compiling buildroot

I updated my buildroot for the version "2014.08" (stable version) and I updated the Kernel version (3.12.26) of my project, when the buildroot try to build the linux-headers-3.12.26 package, occurs ...
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0answers
21 views

What exactly does struct nfs_unlinkdata do?

I been reading the source code of unlink() but i am stuck on nfs_unlinkdata and i can't find anything on it on the web. Thanks a lot for your help.
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0answers
28 views

HD 4800 lower fan speed

I've installed Linux Mint 17, most important thing for me is to lower the fan speed to 30% as I am doing in Windows because it's really too noisy. Note that the temperature stays at ~50°, so this ...
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0answers
27 views

real time kernel / low latency comes from the vanilla source

Does the vanilla source provide real time / low latency functionality ?
3
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0answers
26 views

NTPD Nanokernel

I had a couple of questions about the NTP Nanokernel as explained here: http://www.eecis.udel.edu/~mills/database/brief/nano/nano.pdf The big question is how does this Nanokernel manage to deliver an ...
0
votes
1answer
20 views

module prints to kernel log with delay

I've created a basic linux kernel module, which does the following: static __init int init(void) { printk(KERN_DEBUG "Banana"); return 0; } And of course: module_init(init); Strangely, I ...
2
votes
1answer
26 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 ...
2
votes
1answer
64 views

Does each network packet cause an interrupt to CPU?

While I know that lot of packet processing(CRC calculations, packet segmentation handling, etc) can be offloaded to NIC, then does each packet still cause an interrupt to CPU? Is there a difference if ...
0
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0answers
50 views

latest arch linux on beaglebone black

I have installed arch linux using what I assumed was the latest kernel at http://archlinuxarm.org/os/ArchLinuxARM-am33x-latest.tar.gz But this only installs 3.8.13 and I understand that there are ...
0
votes
1answer
30 views

Changing linux config from 32 bit to 64 bit loses RTC

I have a config from a 32-bit linux 3.12.18, and was trying to compile a 64 bit version with most settings like selected drivers etc. the same as in 32 bit version. For this I used make menuconfig ...
0
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0answers
38 views

Changing CPU frequency programmatically

I have seen that standard CPU Frequency driver(comes with default package with linux kernel) can change the CPU frequency at runtime, when being used under the supervision of "Ondemand" governor. ...
1
vote
1answer
137 views

Kernel 3.14 not working with ATIProprietary fglrx?

On my debian laptop I installed kernel 3.14 so I have the alx driver so my ethernet works, I originally had the 3.2 kernel (Debian 7.7). AFter installing the new kernel, gnome3 went back to the ...
12
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2answers
842 views

memory limit of the Linux kernel

I have a perplexing problem. I have a library which uses sg for executing customized CDBs. There are a couple of systems which routinely have issues with memory allocation in sg. Usually, the sg ...
1
vote
1answer
44 views

Walk-through into make (menu)config's options [closed]

I need to customize the kernel a lot for a custom system. Most of my changes concern the kernel's memory usage (something like an embedded kernel). There are a lot of things enabled by default in the ...
0
votes
2answers
44 views

Fatal error: linux/smp_lock.h: no such file or directory when trying to compile tiusb

I am trying to compile the TI-Graph Link USB Drivers? So I downloaded it, and ran make in the directory libusb. It produced the following: ~/Téléchargements/tiusb/tiusb-1.10$ make make -C ...
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0answers
56 views

How to suppress input overrun messages

I have a Raspberry Pi running Raspbian (a Debian flavor: Linux version 3.12-1-rpi (debian-kernel@lists.debian.org) (gcc version 4.7.2 (Debian 4.7.2-5+rpi1) ) #1 Debian 3.12.9-1+rpi1 (2014-05-19) ). ...
5
votes
1answer
144 views

Calls to sync/fsync slow down after 30 minutes uptime

After 30 minutes of uptime using Ubuntu 14.04 with a hybrid SSD I see many processes blocking IO using iotop. This is during disk writes, for example if I open and close an empty file in gedit it can ...
3
votes
1answer
441 views

Turning off power to usb port. Or turn off power to entire usb subsystem

I have a usb lamp which I specifically bought in order to turn it off programmatically at a certain time, thus I need to remove the power to its usb port. I believe I have a usb-hub at usb6. The lamp ...
1
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0answers
39 views

can't filter printk messages

I'm writing a driver and usually I implement my own log-level scheme. However, this time I figured that I would try to utilize the printk scheme that is built into Linux. I see that I can adjust the ...
1
vote
0answers
33 views

open() sys call [closed]

Process A wants to open a file fd1 = open("/var/file1", O_RDONLY); In the process of opening file1 which table is referred first system wide file table or file descriptor table or in-core inode ...
0
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0answers
26 views

How can I compile and run a program designed for an older kernel version (2.6) in a newer kernel (3.16)?

I'm trying to run a driver for a network card, but it only supports kernels up to 2.6.32. I need to be able to use this piece of hardware to connect to the Internet. The device I'm using is "VIA ...