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Not able to generate race condition

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#142 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Documentation
Clarity
Needs clarification
Activity status
Stale
Tech stack
c
Domain
operating-systems

Research direction

Start by compiling and running the supplied pthread program, then inspect its printed counter values and final check value. Review the behavior of the shared updates and the absence of synchronization; done means providing an explanation grounded in the observed output and identifying what the example demonstrates.

Written by the indexing model from the issue text.

Description

I wrote a code using pthreads where multiple threads were accessing and modifying a global variable and race condition should occur without any locking mechanism or atomic operations but it was not the case. Can anyone explain why this did not occur?
The code is as follows:

#include<stdio.h> 
#include<string.h> 
#include<pthread.h> 
#include<stdlib.h> 
#include<unistd.h> 
#include<stdbool.h>

#define NTHREADS 150
  
pthread_t tid[NTHREADS]; 
int counter; 
pthread_mutex_t lock; 
int check = 3;
  
void* trythis(void *arg) 
{ 
    unsigned long i = 0; 
    // pthread_mutex_lock(&lock);
    counter += 1; 
    // pthread_mutex_unlock(&lock);
    printf("\n Job %d has started\n", counter); 
    check+=1;
    printf("\n Job %d has finished\n", counter); 
     check+=1;
  
    return NULL; 
} 
  
int main(void) 
{ 
    int i = 0; 
    int error; 
  
    if (pthread_mutex_init(&lock, NULL) != 0) 
    { 
        printf("\n mutex init has failed\n"); 
        return 1; 
    } 
  
    while(i < NTHREADS) 
    { 
        error = pthread_create(&(tid[i]), NULL, &trythis, NULL); 
        if (error != 0) 
            printf("\nThread can't be created :[%s]", strerror(error)); 
        i++; 
    } 
  
    for(i=0;i<NTHREADS;i++){
      pthread_join(tid[i],NULL);
    } 
    pthread_mutex_destroy(&lock);
    printf("%d\n",check ); 
  
    return 0; 
}
Dominant language
WebAssembly
Stars
767
Forks
54
No merged PRs in 30d

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