kern_synch.c

早期freebsd实现

		p->p_flag |= P_SINTR;
		if (sig = CURSIG(p)) {
			if (p->p_wchan)
				unsleep(p);
			p->p_stat = SRUN;
			goto resume;
		}
		if (p->p_wchan == 0) {
			catch = 0;
			goto resume;
		}
	} else
		sig = 0;
	p->p_stat = SSLEEP;
	p->p_stats->p_ru.ru_nvcsw++;
	mi_switch();
resume:
	curpriority = p->p_usrpri;
	splx(s);
	p->p_flag &= ~P_SINTR;
	if (p->p_flag & P_TIMEOUT) {
		p->p_flag &= ~P_TIMEOUT;
		if (sig == 0) {
#ifdef KTRACE
			if (KTRPOINT(p, KTR_CSW))
				ktrcsw(p->p_tracep, 0, 0);
#endif
			return (EWOULDBLOCK);
		}
	} else if (timo)
		untimeout(endtsleep, (void *)p);
	if (catch && (sig != 0 || (sig = CURSIG(p)))) {
#ifdef KTRACE
		if (KTRPOINT(p, KTR_CSW))
			ktrcsw(p->p_tracep, 0, 0);
#endif
		if (p->p_sigacts->ps_sigintr & sigmask(sig))
			return (EINTR);
		return (ERESTART);
	}
#ifdef KTRACE
	if (KTRPOINT(p, KTR_CSW))
		ktrcsw(p->p_tracep, 0, 0);
#endif
	return (0);
}

/*
 * Implement timeout for tsleep.
 * If process hasn't been awakened (wchan non-zero),
 * set timeout flag and undo the sleep.  If proc
 * is stopped, just unsleep so it will remain stopped.
 */
void
endtsleep(arg)
	void *arg;
{
	register struct proc *p;
	int s;

	p = (struct proc *)arg;
	s = splhigh();
	if (p->p_wchan) {
		if (p->p_stat == SSLEEP)
			setrunnable(p);
		else
			unsleep(p);
		p->p_flag |= P_TIMEOUT;
	}
	splx(s);
}

/*
 * Short-term, non-interruptable sleep.
 */
void
sleep(ident, priority)
	void *ident;
	int priority;
{
	register struct proc *p = curproc;
	register struct slpque *qp;
	register s;
	extern int cold;

#ifdef DIAGNOSTIC
	if (priority > PZERO) {
		printf("sleep called with priority %d > PZERO, wchan: %x\n",
		    priority, ident);
		panic("old sleep");
	}
#endif
	s = splhigh();
	if (cold || panicstr) {
		/*
		 * After a panic, or during autoconfiguration,
		 * just give interrupts a chance, then just return;
		 * don't run any other procs or panic below,
		 * in case this is the idle process and already asleep.
		 */
		splx(safepri);
		splx(s);
		return;
	}
#ifdef DIAGNOSTIC
	if (ident == NULL || p->p_stat != SRUN || p->p_back)
		panic("sleep");
#endif
	p->p_wchan = ident;
	p->p_wmesg = NULL;
	p->p_slptime = 0;
	p->p_priority = priority;
	qp = &slpque[LOOKUP(ident)];
	if (qp->sq_head == 0)
		qp->sq_head = p;
	else
		*qp->sq_tailp = p;
	*(qp->sq_tailp = &p->p_forw) = 0;
	p->p_stat = SSLEEP;
	p->p_stats->p_ru.ru_nvcsw++;
#ifdef KTRACE
	if (KTRPOINT(p, KTR_CSW))
		ktrcsw(p->p_tracep, 1, 0);
#endif
	mi_switch();
#ifdef KTRACE
	if (KTRPOINT(p, KTR_CSW))
		ktrcsw(p->p_tracep, 0, 0);
#endif
	curpriority = p->p_usrpri;
	splx(s);
}

/*
 * Remove a process from its wait queue
 */
void
unsleep(p)
	register struct proc *p;
{
	register struct slpque *qp;
	register struct proc **hp;
	int s;

	s = splhigh();
	if (p->p_wchan) {
		hp = &(qp = &slpque[LOOKUP(p->p_wchan)])->sq_head;
		while (*hp != p)
			hp = &(*hp)->p_forw;
		*hp = p->p_forw;
		if (qp->sq_tailp == &p->p_forw)
			qp->sq_tailp = hp;
		p->p_wchan = 0;
	}
	splx(s);
}

/*
 * Make all processes sleeping on the specified identifier runnable.
 */
void
wakeup(ident)
	register void *ident;
{
	register struct slpque *qp;
	register struct proc *p, **q;
	int s;

	s = splhigh();
	qp = &slpque[LOOKUP(ident)];
restart:
	for (q = &qp->sq_head; p = *q; ) {
#ifdef DIAGNOSTIC
		if (p->p_back || p->p_stat != SSLEEP && p->p_stat != SSTOP)
			panic("wakeup");
#endif
		if (p->p_wchan == ident) {
			p->p_wchan = 0;
			*q = p->p_forw;
			if (qp->sq_tailp == &p->p_forw)
				qp->sq_tailp = q;
			if (p->p_stat == SSLEEP) {
				/* OPTIMIZED EXPANSION OF setrunnable(p); */
				if (p->p_slptime > 1)
					updatepri(p);
				p->p_slptime = 0;
				p->p_stat = SRUN;
				if (p->p_flag & P_INMEM)
					setrunqueue(p);
				/*
				 * Since curpriority is a user priority,
				 * p->p_priority is always better than
				 * curpriority.
				 */
				if ((p->p_flag & P_INMEM) == 0)
					wakeup((caddr_t)&proc0);
				else
					need_resched();
				/* END INLINE EXPANSION */
				goto restart;
			}
		} else
			q = &p->p_forw;
	}
	splx(s);
}

/*
 * The machine independent parts of mi_switch().
 * Must be called at splstatclock() or higher.
 */
void
mi_switch()
{
	register struct proc *p = curproc;	/* XXX */
	register struct rlimit *rlim;
	register long s, u;
	struct timeval tv;

	/*
	 * Compute the amount of time during which the current
	 * process was running, and add that to its total so far.
	 */
	microtime(&tv);
	u = p->p_rtime.tv_usec + (tv.tv_usec - runtime.tv_usec);
	s = p->p_rtime.tv_sec + (tv.tv_sec - runtime.tv_sec);
	if (u < 0) {
		u += 1000000;
		s--;
	} else if (u >= 1000000) {
		u -= 1000000;
		s++;
	}
	p->p_rtime.tv_usec = u;
	p->p_rtime.tv_sec = s;

	/*
	 * Check if the process exceeds its cpu resource allocation.
	 * If over max, kill it.  In any case, if it has run for more
	 * than 10 minutes, reduce priority to give others a chance.
	 */
	rlim = &p->p_rlimit[RLIMIT_CPU];
	if (s >= rlim->rlim_cur) {
		if (s >= rlim->rlim_max)
			psignal(p, SIGKILL);
		else {
			psignal(p, SIGXCPU);
			if (rlim->rlim_cur < rlim->rlim_max)
				rlim->rlim_cur += 5;
		}
	}
	if (s > 10 * 60 && p->p_ucred->cr_uid && p->p_nice == NZERO) {
		p->p_nice = NZERO + 4;
		resetpriority(p);
	}

	/*
	 * Pick a new current process and record its start time.
	 */
	cnt.v_swtch++;
	cpu_switch(p);
	microtime(&runtime);
}

/*
 * Initialize the (doubly-linked) run queues
 * to be empty.
 */
rqinit()
{
	register int i;

	for (i = 0; i < NQS; i++)
		qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i];
}

/*
 * Change process state to be runnable,
 * placing it on the run queue if it is in memory,
 * and awakening the swapper if it isn't in memory.
 */
void
setrunnable(p)
	register struct proc *p;
{
	register int s;

	s = splhigh();
	switch (p->p_stat) {
	case 0:
	case SRUN:
	case SZOMB:
	default:
		panic("setrunnable");
	case SSTOP:
	case SSLEEP:
		unsleep(p);		/* e.g. when sending signals */
		break;

	case SIDL:
		break;
	}
	p->p_stat = SRUN;
	if (p->p_flag & P_INMEM)
		setrunqueue(p);
	splx(s);
	if (p->p_slptime > 1)
		updatepri(p);
	p->p_slptime = 0;
	if ((p->p_flag & P_INMEM) == 0)
		wakeup((caddr_t)&proc0);
	else if (p->p_priority < curpriority)
		need_resched();
}

/*
 * Compute the priority of a process when running in user mode.
 * Arrange to reschedule if the resulting priority is better
 * than that of the current process.
 */
void
resetpriority(p)
	register struct proc *p;
{
	register unsigned int newpriority;

	newpriority = PUSER + p->p_estcpu / 4 + 2 * p->p_nice;
	newpriority = min(newpriority, MAXPRI);
	p->p_usrpri = newpriority;
	if (newpriority < curpriority)
		need_resched();
}