86 lines
1.7 KiB
C
86 lines
1.7 KiB
C
/*
|
|
* mutex3.c - Shows the deadlock behavior that can happen when
|
|
* a thread attempts to lock a mutex that it has already
|
|
* locked
|
|
*/
|
|
|
|
#include <pthread.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <sys/types.h>
|
|
#include <unistd.h>
|
|
|
|
// shared global
|
|
static int counter1 = 0;
|
|
static int counter2 = 0;
|
|
|
|
// start flag
|
|
volatile int start;
|
|
|
|
// flag mutex
|
|
pthread_mutex_t flag = PTHREAD_MUTEX_INITIALIZER;
|
|
|
|
// The thread process
|
|
void *thread_routine(void *args)
|
|
{
|
|
int me = *((int *)args);
|
|
|
|
int you = me ? 0 : 1;
|
|
|
|
printf("Worker thread: %d ready, you are %d\n", me, you);
|
|
|
|
// wait for start from master thread
|
|
while (!start)
|
|
;
|
|
|
|
for (int j = 0; j < 1000000; j++)
|
|
{
|
|
pthread_mutex_lock(&flag);
|
|
if (me == 0)
|
|
{
|
|
pthread_mutex_lock(&flag);
|
|
}
|
|
|
|
// this is the critical section
|
|
counter1++;
|
|
counter2++;
|
|
// leaving critical section
|
|
pthread_mutex_unlock(&flag);
|
|
}
|
|
|
|
printf("Worker thread: %d done\n", me);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
// Main process
|
|
int main()
|
|
{
|
|
int val1 = 0;
|
|
int val2 = 1;
|
|
|
|
pthread_t thr1;
|
|
pthread_t thr2;
|
|
if (pthread_create(&thr1, NULL, thread_routine, (void *)&val1) == -1)
|
|
{
|
|
printf("COULD NOT CREATE A THREAD\n");
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
if (pthread_create(&thr2, NULL, thread_routine, (void *)&val2) == -1)
|
|
{
|
|
printf("COULD NOT CREATE A THREAD\n");
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
start = 1;
|
|
|
|
pthread_join(thr1, NULL);
|
|
pthread_join(thr2, NULL);
|
|
|
|
printf("counter1: %d\n", counter1);
|
|
printf("counter2: %d\n", counter2);
|
|
|
|
pthread_mutex_destroy(&flag);
|
|
return EXIT_SUCCESS;
|
|
}
|