kernel API to return now running cpu number

Question

I am looking for a Linux kernel API that returns the core number currently executing the task. So I want to know in my code on which particular core is being executed.

I found answer at https://stackoverflow.com/questions/7315907/how-to-find-physical-and-logical-core-number-in-a-kernel-module/7316216 — Mark, Sep 13 '17 at 15:44
Possible duplicate of [How to find physical and logical core number in a kernel module?](https://stackoverflow.com/questions/7315907/how-to-find-physical-and-logical-core-number-in-a-kernel-module) — Tsyvarev, Sep 13 '17 at 19:20
judging by the answers, it seems unclear you are talking about user context or kernel context. — Ezequiel Garcia, Sep 14 '17 at 18:01

score 3 · Answer 1 · edited Jun 20 '20 at 09:12

typically when you are locking a process to a core you use get_cpu this is to prevent preemption so that your process doesn't suddenly move to another CPU. If you know that you're not going to be preempted you can use smp_processor_id to get the CPU id.

  #include/asm/smp.h
  
  static int my_cpu() {
       return smp_processor_id();
  }

NOTES

CPU ids are between 0 and NR_CPUS and they are not necessarily continuous

score 0 · Answer 2 · answered Sep 13 '17 at 15:42

Already answered:

how can I get the processor ID of the current process in C in Linux?

See man page:

http://man7.org/linux/man-pages/man2/getcpu.2.html

tldr:

#include <linux/getcpu.h>

int getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache);

kernel API to return now running cpu number

2 Answers2

NOTES