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@abhinavsingh
Last active September 9, 2015 07:56
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What's the real order? Order in which friend threads were spawned or the ticket id that they came back with?
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
static int ticketid = 0;
pthread_mutex_t lock;
// buyticket function remote dial a central store to obtain ticket id
void * buyticket() {
int *id = (int *)malloc(sizeof(int));
pthread_mutex_lock(&lock);
*id = ticketid++;
pthread_mutex_unlock(&lock);
return id;
}
void * friend(void *arg) {
return buyticket();
}
int main() {
// N friends one by one to go buy ticket
int N = 10;
int i;
pthread_t friends[N];
for (i=0; i<N; i++) {
// imagine spawn of thread as u saying to friends on Node A, B, C ... to buy a ticket in order
pthread_create(&friends[i], NULL, friend, NULL);
}
// wait for friends to come back
int *id;
for (i=0; i<N; i++) {
pthread_join(friends[i], (void **)&id);
printf("friend id %d, ticket id %d\n", i, *id);
free(id);
}
}
@abhinavsingh
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This code is not to say that above strategy is correct, but more to imply that how ordering of operations are simply lost as soon as you start to multi-thread the client side.

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