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Questions tagged [interrupt]

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linux kernel freeze

I am using linux kernel 4.19 on intel (icelake) based server. Sometime immediately after linux boot (at the login prompt) it get stuck(once is 50 reboot or so). It is not responding to anything on ...
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How can I ensure that my linux laptop will not wake up from sleep when the lid is closed?

I have a Linux laptop that at seemingly random times of the day wakes up despite that the lid is closed. How can I make sure it either doesn't wake up or if it DOES wake up, goes back to sleep again? ...
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-1 votes
1 answer
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Modify the number of interruption cat /proc/interruption

As you can see, when running the command cat /proc/interrupts, in the second column the number of interrupts delivered to each CPU per device driver. test@test:~$ cat /proc/interrupts CPU0 ...
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Interpreting variations in LOCal timer interrupts number

Running a given workload in different CPU isolation (IRQs & processes) configurations, I do not observe significant differences among values (grand total) reported in /proc/interrupts & /proc/...
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What are unnumbered interrupts in /proc/stat?

According to man page for the /proc/stat "intr" field: The first column is the total of all interrupts serviced including unnumbered architecture specific interrupts; each subsequent column ...
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how to interrupt command initramfs

I have made a huge mistake. I'm currently loaded into initramfs, trying to fix an error similar to this post. I decided to cat /dev/XXXX, where I'm pretty sure XXXX is the main partition where Ubuntu ...
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1 vote
2 answers
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Halt execution of pasted multiline commands

I pasted a long list of commands into Bash, and in the middle of execution, I decided I wanted it to stop. Ctrl+Z and Ctrl+C did nothing. It just continues executing line after line. In the end, the ...
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1 answer
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Setting a trap for INT doesn't work in a subshell

$ bash -c "trap \"echo INT\" INT; sleep 3" & pid=$!; sleep 1; kill -INT $pid; wait [1] 27811 INT [1]+ Done bash -c "trap \"echo INT\" INT; ...
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EXIT trap is ignored on Ctrl-C when PID == 1

a.sh: trap 'echo cleanup' EXIT sleep 3 To reproduce, press Ctrl-C before the script finishes: $ docker run --rm -itv $PWD:/app -w /app alpine:3.14 sh a.sh ^Ccleanup $ docker run --rm -itv $PWD:/app -...
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Tracking interrupts on RPI

Currently writing a program which runs on a Raspberry Pi3 (Linux) which needs to get as close to real time collection of data as possible. I have set its policy to FIFO and given it the highest ...
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Can APIC LVTERR on AMD be configured as NMI message type?

In fact, the message type / delivery mode of LVTERR on Intel is unconfigured. However, on AMD, it is presented as below. The problem is, when I configure the MT of LVTERR on AMD as NMI, it will keep ...
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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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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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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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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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2 votes
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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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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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2 votes
2 answers
159 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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1 vote
1 answer
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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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1 vote
1 answer
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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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1 answer
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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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1 vote
1 answer
501 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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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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12 votes
1 answer
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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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2 votes
1 answer
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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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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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1 answer
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__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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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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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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5 votes
2 answers
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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2 votes
1 answer
164 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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2 votes
0 answers
319 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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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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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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1 answer
949 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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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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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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6 votes
2 answers
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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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5 votes
1 answer
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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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6 votes
1 answer
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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4 votes
2 answers
4k 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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2 votes
0 answers
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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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3 votes
1 answer
810 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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2 votes
3 answers
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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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8 votes
1 answer
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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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1 answer
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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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2 votes
0 answers
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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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1 answer
307 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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