Function startprofclock

freebsd/kern/kern_clock.c:591–605

* Start profiling on a process. * * Kernel profiling passes proc0 which never exits and hence * keeps the profile clock running constantly. */

 * keeps the profile clock running constantly.
 */
void
startprofclock(struct proc *p)
{

	PROC_LOCK_ASSERT(p, MA_OWNED);
	if (p->p_flag & P_STOPPROF)
		return;
	if ((p->p_flag & P_PROFIL) == 0) {
		p->p_flag |= P_PROFIL;
		mtx_lock(&time_lock);
		if (++profprocs == 1)
			cpu_startprofclock();
		mtx_unlock(&time_lock);
	}
}

/*
 * Stop profiling on a process.