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#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
/* Simple test program, no race: parent only modifies x after child
has modified it and then joined with the parent. Tests simple
thread lifetime segment handling. */
/* A simple function to "use" a value, so that gcc can't
possibly optimise it into nothing. */
static void use ( int x ) {
__asm__ __volatile__( "nop" : : "r"(x) : "cc","memory" );
}
static void* worker_thread ( void* argV )
{
int* arg = (int*)argV;
use(arg[5]); /* read access */
return NULL;
}
int main ( void )
{
pthread_t thread_id;
volatile int* x = malloc(10 * sizeof(int));
x[5] = 1;
/* x[5] is Excl(parent) */
pthread_create(&thread_id, 0, worker_thread, (void*)x);
use(x[5]); /* read access */
/* Just before the threads join, x[5] is ShR (read by both parent
and child) */
pthread_join(thread_id, 0);
/* x[5] is Excl(parent), because only parent and child accessed it
and child has merged to parent. So now it's ok for parent to
access it without locking. */
x[5] = 0; /* write access */
return x[5];
}
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