| 1 | // SPDX-License-Identifier: GPL-3.0-or-later |
| 2 | |
| 3 | /* |
| 4 | * A very simple pthreads program to spawn N busy threads. |
| 5 | * It is just used for validating apps.plugin CPU utilization |
| 6 | * calculations per operating system. |
| 7 | * |
| 8 | * Compile with: |
| 9 | * |
| 10 | * gcc -O2 -ggdb -o busy_threads busy_threads.c -pthread |
| 11 | * |
| 12 | * Run as: |
| 13 | * |
| 14 | * busy_threads 2 |
| 15 | * |
| 16 | * The above will create 2 busy threads, each using 1 core in user time. |
| 17 | * |
| 18 | */ |
| 19 | |
| 20 | #include <stdio.h> |
| 21 | #include <stdlib.h> |
| 22 | #include <pthread.h> |
| 23 | #include <signal.h> |
| 24 | #include <unistd.h> |
| 25 | |
| 26 | volatile int keep_running = 1; |
| 27 | |
| 28 | void handle_signal(int signal) { |
| 29 | keep_running = 0; |
| 30 | } |
| 31 | |
| 32 | void *busy_loop(void *arg) { |
| 33 | while (keep_running) { |
| 34 | // Busy loop to keep CPU at 100% |
| 35 | } |
| 36 | return NULL; |
| 37 | } |
| 38 | |
| 39 | int main(int argc, char *argv[]) { |
| 40 | if (argc != 2) { |
| 41 | fprintf(stderr, "Usage: %s <number of threads>\n", argv[0]); |
| 42 | exit(EXIT_FAILURE); |
| 43 | } |
| 44 | |
| 45 | int num_threads = atoi(argv[1]); |
| 46 | if (num_threads <= 0) { |
| 47 | fprintf(stderr, "Number of threads must be a positive integer.\n"); |
| 48 | exit(EXIT_FAILURE); |
| 49 | } |
| 50 | |
| 51 | // Register the signal handler to gracefully exit on Ctrl-C |
| 52 | signal(SIGINT, handle_signal); |
| 53 | |
| 54 | pthread_t *threads = malloc(sizeof(pthread_t) * num_threads); |
| 55 | if (threads == NULL) { |
| 56 | perror("malloc"); |
| 57 | exit(EXIT_FAILURE); |
| 58 | } |
| 59 | |
| 60 | // Create threads |
| 61 | for (int i = 0; i < num_threads; i++) { |
| 62 | if (pthread_create(&threads[i], NULL, busy_loop, NULL) != 0) { |
| 63 | perror("pthread_create"); |
| 64 | free(threads); |
| 65 | exit(EXIT_FAILURE); |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | // Wait for threads to finish (they never will unless interrupted) |
| 70 | for (int i = 0; i < num_threads; i++) { |
| 71 | pthread_join(threads[i], NULL); |
| 72 | } |
| 73 | |
| 74 | free(threads); |
| 75 | return 0; |
| 76 | } |