#include <sys/types.h>
#include <sys/usched.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>

/*
 * DF-4260 per-CPU timer witness: pin this process to <cpu> with
 * usched_set(2) (4-arg form: pid, cmd, data, bytes) and sleep 3s.
 * On a CPU whose softclock thread is wedged by the deadlock, the
 * sleep never wakes (its tsleep timeout callout is queued on the
 * dead softclock) and only timeout(1)'s SIGTERM ends the process
 * (rc=124 after 8s).  Healthy CPUs: rc=0 after ~3s.
 */
int main(int argc, char **argv)
{
	int cpu;

	if (argc != 2)
		return 2;
	cpu = atoi(argv[1]);
	if (usched_set(0, USCHED_SET_CPU, &cpu, sizeof(cpu)) != 0) {
		fprintf(stderr, "usched_set: %s\n", strerror(errno));
		return 2;
	}
	sleep(3);
	return 0;
}