a case for helgrind

posix-helgrind.c

/*
 * make:
 *	gcc -g posixtest.c -pthread -o posixtest
 * run:
 *	valgrind --tool=helgrind ./posixtest
 */
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>

pthread_rwlock_t lock1;
pthread_rwlock_t lock2;
pthread_rwlock_t lock3;

static void *dowork(void *x)
{
	pthread_rwlock_t *lock = (pthread_rwlock_t*)x;
	sleep(3);
	pthread_rwlock_unlock(lock);

	return NULL;
}

int main()
{
	pthread_rwlock_init(&lock1, NULL);
	pthread_rwlock_init(&lock2, NULL);
	pthread_rwlock_init(&lock3, NULL);

	// case#1: lock order
	pthread_rwlock_wrlock(&lock1);
	pthread_rwlock_wrlock(&lock2);
	pthread_rwlock_wrlock(&lock3);

	pthread_rwlock_unlock(&lock1);
	pthread_rwlock_unlock(&lock2);
	pthread_rwlock_unlock(&lock3);


	// case#2: unlock2 in background thread, casused helgrind incorrect warning
	pthread_rwlock_wrlock(&lock2);
	pthread_t t1;
	pthread_create(&t1, NULL, dowork, (void*)&lock2);

	pthread_rwlock_wrlock(&lock1);
	pthread_rwlock_unlock(&lock1);
	pthread_join(t1, NULL);

	return 1;
}