gistfile1.txt

#include <sys/types.h>
#include <sys/param.h>

#include <sys/kernel.h>
#include <sys/kthread.h>

#define NTHREADS 4
#define MAX_ITERATIONS 5000

static volatile int elements[NTHREADS] = {0};

void
main()
{
	lwp_t **l;
	int i;
	for (i = 0; i < NTHREADS; ++i) {
		error = kthread_create(PRI_NONE, KTHREAD_MPSAFE, i,
		    thread_run, i, &l[i], "kernellocktest");
		KASSERT(error == 0);
	}
}

void
thread_run(unsigned thread_no)
{
	int i;
	int j;
	for (j = 0; j < MAX_ITERATIONS; ++j) {
		KERNEL_LOCK(1, NULL);

		elements[thread_no] = 1;

		for (i = 0; i < NTHREADS; ++i) {
			if (i != thread_no)
				KASSERTMSG(elements[i] == 0,
				    "the impossible has happened");
		}

		elements[thread_no] = 0;
		KERNEL_UNLOCK_ONE(NULL);
	}
}