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Questions tagged [interrupt]

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Trouble with Legacy interrupts on new CPU

A legacy (IntA) interrupt works on an old CPU under Linux, but fails under the same Linux OS with a newer CPU in that system. I'm unsure if the problem is in the BIOS or in the Linux driver, as both ...
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What is interrupted system call?

I am reading APUE and the Interrupted System Calls chapter confuses me. I would like to write down my understanding based on the book, please correct me. A characteristic of earlier UNIX systems ...
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Trying to use local APIC timer

I'm trying to use the local APIC timer to send interrupts after a certain interval (for a kernel module I am writing). This is not related to scheduling in Linux. I set the clocksource in Linux to ...
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1answer
112 views

How does Linux Kernel switches from kernel stack to interrupt stack?

What happens when a user mode task is interrupted ? I know for a fact that the CPU switches to the kernel mode stack by refring the TSS. But when and how does the kernel switches to the IRQ stack?
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About IRQF_DISABLED flags

I'm reading about a tutorial on request_irq, I'm new to this topic so I need some idea checking: When set, this flag instructs the kernel to disable all interrupts when executing this interrupt ...
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1answer
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Resource locking in interrupts

I have a kernel module with netfilter hooks at different points in the packet route, and the hooks use shared resources. In addition, the module has a char device that may be written to, that also ...
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Interrupt handling with separate thread

The Situation A kernel driver handles interrupts coming from a CPU pin. The interrupt handler function wakes up a thread function which reads data from an interface. There is one interrupt per data ...
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2answers
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Are interrupts used to signify that output is ready or input has completed?

Operating System Concepts says: During I/O, the various device controllers raise interrupts when they are ready for service. These interrupts signify that output has completed, or ...
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Interrupt signal names don't work over ssh: bad trap [duplicate]

If run over ssh, a script with a trap statement with interrupt signal names (SIGINT, etc) gives an error and the trap does not work when an interrupt (eg. Ctrl+C) is sent. Eg: #!/bin/bash trap '...
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1answer
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How to ignore interrupts with piped commands

In the following chain of piped commands, when an interrupt is sent with Ctrl-C, ping is able to print its summary statistics before exiting, as long as tee has the -i (ignore interrupts) flag: ping -...
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how to use ftrace to function_trace a kernel modules interrupt?

I have a Banana Pi Arm device with 2 cores (1.2 GHz) running a Debian kernel which I enabled ftrace kernel debug options. I want to determine the amount of time spent in a kernel module function. The ...
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1answer
229 views

How does the kernel scheduler know a timeslice has passed?

In my previous question How does the kernel scheduler know how to pre-empt a process? I was given an answer to how pre-emption occurs. Now I am wondering, how does the kernel scheduler know that a ...
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How does the kernel scheduler know how to pre-empt a process?

As far as I understand, the kernel is not a process, but rather a set of handlers that can be invoked from the runtime of another progress (or by the kernel itself via a timer or something similar?) ...
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Why does nohup command interrupt?

I put a command in .bash_profile file. The command is: nohup stdbuf -oL -eL sysdig -c spy_users 1>>/path/to/out 2>>/path/to/err & While I am working on terminal it appears: [1]+ ...
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Is there a way to route interrupts from two Ethernet interfaces to separate cores?

I have a 10G ethernet adapter from Intel with two ethernet ports (x550-T2) installed in PCIe port of a Xilinx FPGA board running petalinux. I am testing network bandwidth by running simultaneous ...
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1answer
679 views

can't change value in smp_affinity

I am trying to set irq affinity on linux by changing the value in smp_affinity. When I echo the new value into the file, I don't get any error but when I read it back, the value remains unchanged. I ...
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1answer
197 views

Saving data from kernel module into userspace

I have been playing around kernel programming for a while and want to create this simple data acquiring interface with some custom hardware. For portability and reusability, I do the whole thing on my ...
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1answer
60 views

Can a hardware generating too many interruptions monopolize a CPU?

Let's say my network interface is receiving too many packets and I have a single-core processor. What stops it (if anything) to keep interrupting the kernel and essentially monopolize the CPU (top-...
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difference between kworker/n and events/n

I'm learning how the kernel handles interrupt. Reading shichao's notes, I've found that events/n threads handle the work queue. At the same time, some documents in the internet (for example, this post)...
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Shielding CPU from scheduler - How to move bound kernel threads from cores?

Suppose I have 4 physical cores (indexed 0-3) and I'm dedicating cores 1-3 to a shield for user applications and trying to steer all system threads onto core 0. I'm following the answers here and ...
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1answer
604 views

Regarding /proc/interrupts what are MIS and ERR?

Playing aroud looking at /proc/interrupts The output below shows ERR and MIS on lines 26 and 27 respectively. What are these and why do they have counts (albeit of zero) for CPU0 but no others, as ...
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1answer
98 views

How to restrict interrupt signal to just the child process?

I have a bunch of log files and I want to do a tail -f on them in a loop such that when I press Ctrl-C, the current tail -f gets killed and I proceed to the next log file: for log in *.log; do ...
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290 views

Interrupt shell command line expansion

Warning: DO NOT attempt the commands listed in this question without knowing their implications. Sorry if this is a duplicate. I am surprised to learn that a command as simple as echo $(yes) ...
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1answer
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What happens when there is a context switch while the process is in Kernel mode?

This is my understanding: When in user mode and a trap/system call occurs, registers are saved on to the kernel stack, switch is made to kernel mode, and trap is handled and returned to user mode. ...
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1answer
215 views

Identify devices like virtio2 and virtio3 in QEmu

I'm running a virtual machine in QEmu. The following command in the guest VM cat /proc/interrupts | egrep 'virtio.*(input|output)' gives me the following output: 26: 0 3376 0 ...
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1answer
873 views

What does `/proc/irq/…/spurious` contain?

Here is the output from cat /proc/irq/79/spurious: count 28 unhandled 0 last_unhandled 0 ms What are these parameters indicating here — count, last_unhandled? Is this count indicating the number of ...
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1answer
603 views

Unusual high load average (due to peak I/O wait? irqs?)

I have a problem with high load average (~2) on my (personal laptop) computer for a long time now. I am running Arch Linux. If I remember correctly, the problem started with a certain kernel update, ...
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2answers
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What happens when a new hardware is connected for first time in Linux?

Suppose, I have connected a device to a PC. Question: How does the Linux OS (Ubuntu) realizes that a new hardware device is connected? Answer: The newly connected device raises an Interrupt (and ...
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1answer
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How does keyboard interrupt ends up as process signal

I'm studying the linux kernel right know with O'Reilly's Understanding Linux Kernel and lately covered the signal and interrupt handling chapter sticking to some basic 2.4 linux version and diving ...
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1answer
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Why doesn't SIGINT work on a background process in a script?

I have the following in a script: yes >/dev/null & pid=$! echo $pid sleep 2 kill -INT $pid sleep 2 ps aux | grep yes When I run it, the output shows that yes is still running by the end of ...
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1answer
635 views

Confusion regarding #interrupt-cells configuration on PCA9555 expander

I'm trying to setup a device tree source file for the first time on my custom platform. On the board is a NXP PCA9555 gpio expander. I'm attempting to setup node for the device and am a bit confused. ...
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Does the lack of kernel feature (XENFEAT_hvm_pirqs) cause RedHat EC2 interrupt issue?

I have a RedHat 6.5 on AWS EC2 running kernel 2.6.32.431, I have installed the ixgbevf driver with the minimum version the doc recommends. After configuration the system now has 2 queues(IRQs): grep ...
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What does this mean: “Interrupt: pin A routed to IRQ 17”

When I run the command: sudo lspci -vvv, I see the following among the output: 0c:00.0 Network controller: Broadcom Corporation BCM4311 802.11b/g WLAN (rev 01) Subsystem: Dell Wireless 1390 ...
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1answer
4k views

What is the difference between /proc/interrupts and /proc/softirq in Linux?

/proc/softirq is softirq stats. Is /proc/interrupt both hard and soft interrupts or hard only? I want to measure the rate of hard and soft irq's per second roughly using watch -n 1 grep 'foo' /proc/...
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Wifi card causing High interrupts on Fedora 24

I am running Fedora 24 on my MSI cx61 2QC laptop. Occasionally, one of the processor's core becomes monopolized by high irqs from the rtl_pci(wifi) card. The model of the wifi card is RTL8723AE. $ ...
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Trying to understand device tree entry for usart

I'm pretty new to device tree programming, I'm trying to understand the interrupts line that shows up in the device tree for SAMA5D36 USART dts definition: usart2: serial@f8020000 { compatible = "...
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1answer
118 views

Can a program ever receive a software interrupt?

Can a program ever receive a software interrupt? I understand that they can cause interrupts, but can they actually recieve a software interrupt? If so, please can you provide an example?
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Halt the execution when something is written to stderr

I have trouble with error handling in bash scripts. None of the solutions I have seen for error handling in bash seem to work so far for this example script: #!/usr/bin/env bash set -euo pipefail ...
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Apart from USR1 and USR2, which signals can I safely use for custom interrupting behavior? (in python)

I have a complex application with USR1 and USR2 already defined as having a well-defined and not replaceable purpose. There are tons of different signals in linux. Might there be another one (maybe a ...
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1answer
159 views

Hook serial port interrupt in FreeBSD

I need to write a program to react to the modem control lines changing in the serial port on my FreeBSD 10.3 machine. I don't want to read any data from it (there won't be any). I'm aware I can ...
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1answer
2k views

How to test linux NAPI feature?

I am trying to test the NAPI functionalities on embedded linux environment. I used 'pktgen' to generate the large number of packets and tried to verify the interrupt count of my network interface at /...
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1answer
103 views

why local CPU must have interrupts enabled, otherwise kernel preemption is not performed?

I read the book "understanding the Linux kernel". I cannot understand a sentence,that is ,the local CPU must have local interrupts enabled, otherwise kernel preemption is not performed. What is the ...
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kernel: hpet1: lost 19 rtc interrupts

I have this error that flooding my syslog every day. As a solution on arch linux forum is hpet=disable in kernel command line, but I think it is a bad idea and I searching for another solution. Is ...
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1answer
2k views

Programmatically determine the IRQs associated with a network interface

What is the most reliable way to programmatically determine the IRQs associated with a network interface, given the name of the interface (e.g. eth0)? I'm okay with a best-effort approach, but I'd ...
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Why do interrupted processes show up in nvidia-smi?

When ​I kill processes in terminal using C-c and run nvidia-smi, the process are still shown as "compute processes". These processes are no longer in the top resu​lts. I have to kill -9 to clean them (...
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2answers
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The interrupt timeline for a single process doing output

I'm studying the book 'Operating System Concepts' 9th edition. In the first chapter, part 1.2.1 computer system operation, I can't understand the figure 1.3: Can any one make a quick interpretation ...
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1answer
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When is `irqbalance` needed in a Linux VM under VMware?

I have a Linux farm in VMware Enterprise 5.5. The VMs are (mostly) 64-bit amd64 Debian Jessie servers with SysVinit and not systemd. The VMs have open-vm-tools installed. I paravirtualized their ...
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1answer
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Ctrl+c and Ctrl+z to interrupt/suspend jobs

To kill a hanging job, I use Ctrl+c, to send an interrupt signal to the hanging job. Sometimes this wouldn't stop the job, at least not immediately. I can then use Ctrl+z to suspend the job and then ...
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Why I am not able to bind the interrupts with code LOC, IWI, RES when irqbalance is disabled?

On Ubuntu 14.04, I am trying to bind all the interrupts to core 0 and 1 out of 4 cores. I have disabled the irqbalance daemon via file /etc/init/irqbalance.override. Then I went to every interrupt in /...
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1answer
122 views

Interrupt kernel process or another interrupt

How does ISR know that it interrupts process in kernel mode or another interrupt (which enables further interrupts) - of course in kernel mode too. If this question is very wide, please aim to Linux ...