How to implement guide with concurrent access to shared resource using pthreads in c - data corruption
I'm attempting to set up I'm trying to configure I'm trying to debug I'm working on a project and hit a roadblock. I'm working with data corruption issues when using pthreads to access a shared resource in my C program. I have a simple application that uses two threads to increment a global counter. When both threads run simultaneously, the counter sometimes updates incorrectly, resulting in values that are less than expected. Here's a snippet of my code: ```c #include <pthread.h> #include <stdio.h> #include <stdlib.h> volatile int counter = 0; void* increment_counter(void* arg) { for (int i = 0; i < 100000; i++) { counter++; } return NULL; } int main() { pthread_t thread1, thread2; pthread_create(&thread1, NULL, increment_counter, NULL); pthread_create(&thread2, NULL, increment_counter, NULL); pthread_join(thread1, NULL); pthread_join(thread2, NULL); printf("Final counter value: %d\n", counter); return 0; } ``` When I run the application, I sometimes get a final counter value of less than 200000, which indicates that increments are being lost. I've tried using a mutex to protect the increment operation, like this: ```c pthread_mutex_t lock; void* increment_counter(void* arg) { for (int i = 0; i < 100000; i++) { pthread_mutex_lock(&lock); counter++; pthread_mutex_unlock(&lock); } return NULL; } ``` However, I still see some unexpected behavior, especially when I increase the number of increments or use more threads. I'm initializing the mutex in `main()` with `pthread_mutex_init(&lock, NULL);` and destroying it afterward with `pthread_mutex_destroy(&lock);`. I suspect this might be a subtle scenario with how I'm managing thread safety. Any suggestions on what I might be doing wrong? Am I missing an important aspect of using pthreads for shared resources? Any help would be greatly appreciated! This is part of a larger CLI tool I'm building. Any ideas how to fix this? I'm developing on Debian with C. My development environment is macOS. I'd love to hear your thoughts on this.