C++ cv_wait函数代码示例

static
void
cvtestthread(void *junk, unsigned long num)
{
	int i;
	volatile int j;
	time_t secs1, secs2;
	uint32_t nsecs1, nsecs2;

	(void)junk;

	for (i=0; i<NCVLOOPS; i++) {
		lock_acquire(testlock);
		while (testval1 != num) {
			gettime(&secs1, &nsecs1);
			cv_wait(testcv, testlock);
			gettime(&secs2, &nsecs2);

			if (nsecs2 < nsecs1) {
				secs2--;
				nsecs2 += 1000000000;
			}
			
			nsecs2 -= nsecs1;
			secs2 -= secs1;

			/* Require at least 2000 cpu cycles (we're 25mhz) */
			if (secs2==0 && nsecs2 < 40*2000) {
				kprintf("cv_wait took only %u ns\n", nsecs2);
				kprintf("That's too fast... you must be "
					"busy-looping\n");
				V(donesem);
				thread_exit();
			}

		}
		kprintf("Thread %lu\n", num);
		testval1 = (testval1 + NTHREADS - 1)%NTHREADS;

		/*
		 * loop a little while to make sure we can measure the
		 * time waiting on the cv.
		 */
		for (j=0; j<3000; j++);

		cv_broadcast(testcv, testlock);
		lock_release(testlock);
	}
	V(donesem);
}

void
down(struct semaphore *s)
{

	mtx_lock(&s->mtx);
	while (s->value == 0) {
		s->waiters++;
		cv_wait(&s->cv, &s->mtx);
		s->waiters--;
	}

	s->value--;
	mtx_unlock(&s->mtx);
}

static
void
cat(void * unusedpointer, 
    unsigned long catnumber)
{
        int whichBowl = 0; // 0 = neither bowl, 1 = bowlOne, 2 = bowlTwo

	(void) unusedpointer;
        //(void) catnumber;	

	lock_acquire(l);
	//wait until there are no mioce eating and there is at most 1 cat eating
       	while((catsEating > 1) || (miceEating > 0))
	{
		cv_wait(c, l);
	}
	
	//choose a bowl
	if(!bowlOneUsed){
		bowlOneUsed = 1;
		whichBowl = 1;
	}
	else if(!bowlTwoUsed){
		bowlTwoUsed = 1;
		whichBowl = 2;
	}
	else
		panic("No bowl open for cat, even though we waited for an open bowl");

	catsEating++;

	//cat eats
	lock_release(l);
	kprintf("cat %lu starts eating at bowl %d \n", catnumber, whichBowl);
	clocksleep(1);
	kprintf("cat %lu done eating at bowl %d \n", catnumber, whichBowl);
	lock_acquire(l);

	
	if(whichBowl == 1)
		bowlOneUsed = 0;
	else if (whichBowl == 2)
		bowlTwoUsed = 0;
	else
		panic("Neither bowl was used (cat)!");
	catsEating--;
	
	cv_broadcast(c, l);
	lock_release(l);
}

void
flush_workqueue(struct workqueue_struct *wq)
{
	static const struct wq_flush zero_wqf;
	struct wq_flush wqf = zero_wqf;

	mutex_init(&wqf.wqf_lock, MUTEX_DEFAULT, IPL_NONE);
	cv_init(&wqf.wqf_cv, "lnxwflsh");

	if (1) {
		struct wq_flush_work *const wqfw = kmem_zalloc(sizeof(*wqfw),
		    KM_SLEEP);

		wqf.wqf_n = 1;
		wqfw->wqfw_flush = &wqf;
		INIT_WORK(&wqfw->wqfw_work, &linux_wq_barrier);
		wqfw->wqfw_work.w_wq = wq;
		wqfw->wqfw_work.w_state = WORK_PENDING;
		workqueue_enqueue(wq->wq_workqueue, &wqfw->wqfw_work.w_wk,
		    NULL);
	} else {
		struct cpu_info *ci;
		CPU_INFO_ITERATOR cii;
		struct wq_flush_work *wqfw;

		panic("per-CPU Linux workqueues don't work yet!");

		wqf.wqf_n = 0;
		for (CPU_INFO_FOREACH(cii, ci)) {
			wqfw = kmem_zalloc(sizeof(*wqfw), KM_SLEEP);
			mutex_enter(&wqf.wqf_lock);
			wqf.wqf_n++;
			mutex_exit(&wqf.wqf_lock);
			wqfw->wqfw_flush = &wqf;
			INIT_WORK(&wqfw->wqfw_work, &linux_wq_barrier);
			wqfw->wqfw_work.w_state = WORK_PENDING;
			wqfw->wqfw_work.w_wq = wq;
			workqueue_enqueue(wq->wq_workqueue,
			    &wqfw->wqfw_work.w_wk, ci);
		}
	}

	mutex_enter(&wqf.wqf_lock);
	while (0 < wqf.wqf_n)
		cv_wait(&wqf.wqf_cv, &wqf.wqf_lock);
	mutex_exit(&wqf.wqf_lock);

	cv_destroy(&wqf.wqf_cv);
	mutex_destroy(&wqf.wqf_lock);
}

static void
nandfs_wakeup_wait_cleaner(struct nandfs_device *fsdev, int reason)
{

	mtx_lock(&fsdev->nd_clean_mtx);
	if (reason == NANDFS_CLEANER_KILL)
		fsdev->nd_cleaner_exit = 1;
	if (fsdev->nd_cleaning == 0) {
		fsdev->nd_cleaning = 1;
		wakeup(&fsdev->nd_cleaning);
	}
	cv_wait(&fsdev->nd_clean_cv, &fsdev->nd_clean_mtx);
	mtx_unlock(&fsdev->nd_clean_mtx);
}

/*------------------------------------------------------------------------*
 *	usb_proc_drain
 *
 * This function will tear down an USB process, waiting for the
 * currently executing command to return.
 *
 * NOTE: If the structure pointed to by "up" is all zero,
 * this function does nothing.
 *------------------------------------------------------------------------*/
void
usb_proc_drain(struct usb_process *up)
{
	/* check if not initialised */
	if (up->up_mtx == NULL)
		return;
	/* handle special case with Giant */
	if (up->up_mtx != &Giant)
		mtx_assert(up->up_mtx, MA_NOTOWNED);

	mtx_lock(up->up_mtx);

	/* Set the gone flag */

	up->up_gone = 1;

	while (up->up_ptr) {

		/* Check if we need to wakeup the USB process */

		if (up->up_msleep || up->up_csleep) {
			up->up_msleep = 0;
			up->up_csleep = 0;
			cv_signal(&up->up_cv);
		}
		/* Check if we are still cold booted */

		if (cold) {
#ifndef __rtems__
			USB_THREAD_SUSPEND(up->up_ptr);
			printf("WARNING: A USB process has "
			    "been left suspended\n");
			break;
#else /* __rtems__ */
                        BSD_ASSERT(0);
#endif /* __rtems__ */
		}
		cv_wait(&up->up_cv, up->up_mtx);
	}
	/* Check if someone is waiting - should not happen */

	if (up->up_dsleep) {
		up->up_dsleep = 0;
		cv_broadcast(&up->up_drain);
		DPRINTF("WARNING: Someone is waiting "
		    "for USB process drain!\n");
	}
	mtx_unlock(up->up_mtx);
}

/* remove a vldc port */
static int
i_vldc_remove_port(vldc_t *vldcp, uint_t portno)
{
	vldc_port_t *vport;
	vldc_minor_t *vminor;

	ASSERT(vldcp != NULL);
	ASSERT(MUTEX_HELD(&vldcp->lock));

	vport = &(vldcp->port[portno]);
	vminor = vport->minorp;
	if (vminor == NULL) {
		cmn_err(CE_NOTE, "?i_vldc_remove_port: trying to remove a "
		    "port (%u) which is not bound", portno);
		return (MDEG_FAILURE);
	}

	/*
	 * Make sure that all new attempts to open or use the minor node
	 * associated with the port will fail.
	 */
	mutex_enter(&vminor->lock);
	vminor->portno = VLDC_INVALID_PORTNO;
	mutex_exit(&vminor->lock);

	/* send hangup to anyone polling */
	pollwakeup(&vport->poll, POLLHUP);

	/* Now wait for all current users of the minor node to finish. */
	mutex_enter(&vminor->lock);
	while (vminor->in_use > 0) {
		cv_wait(&vminor->cv, &vminor->lock);
	}

	if (vport->status != VLDC_PORT_CLOSED) {
		/* close the port before it is torn down */
		(void) i_vldc_close_port(vldcp, portno);
	}

	/* remove minor node */
	ddi_remove_minor_node(vldcp->dip, vport->minorp->sname);
	vport->minorp = NULL;

	mutex_exit(&vminor->lock);

	D1("i_vldc_remove_port: removed vldc port %u\n", portno);

	return (MDEG_SUCCESS);
}

void *thread_cli_fun(void *arg) {
    double          busy;
    int             inx;
    Msg            *msg;
    struct rusage   r_start;
    struct rusage   r_stop;
    struct timeval  t_elapsed_data;
    struct timeval  t_elapsed_total;
    struct timeval  t_start_data;
    struct timeval  t_start_total;
    struct timeval  t_stop;

    arg = arg; // touch
    util_time_timer_start(&t_start_total);
    util_time_timer_start(&t_start_data);
    util_cpu_timer_start(&r_start);
    for (inx = 0; inx < loop; inx++) {
        if (verbose)
            printf("count=%d\n", inx);
        msg = msg_queue_remove(&mutex_pool, &queue_pool);
        assert(msg != NULL);
        if (csize) {
            msg->cbuf = (char *) malloc(csize);
            memcpy(msg->cbuf, send_buffer2, csize);
        }
        if (dsize) {
            msg->dbuf = (char *) malloc(dsize);
            memcpy(msg->dbuf, send_buffer, dsize);
        }
        msg_queue_add(&mutex_srv, &queue_srv, msg);
        cv_signal(&cv_srv);
        cv_wait(&cv_cli);
        msg = msg_queue_remove(&mutex_cli, &queue_cli);
        assert(msg != NULL);
        msg_queue_add(&mutex_pool, &queue_pool, msg);
    }
    util_cpu_timer_stop(&r_stop);
    util_time_timer_stop(&t_stop);
    util_time_elapsed(&t_start_total, &t_stop, &t_elapsed_total);
    util_time_elapsed(&t_start_data, &t_stop, &t_elapsed_data);
    util_cpu_timer_busy(&r_start, &r_stop, &t_elapsed_data, &busy);

    if (!bm) {
        print_elapsed("", &t_elapsed_total);
        print_elapsed(" (data)", &t_elapsed_data);
    }
    print_rate(bm, "", bidir ? 2 * loop : loop, dsize, &t_elapsed_data, busy);
    return NULL;
}

/* Like sleep, but it will timeout in 'usec' microseconds. */
void rendez_sleep_timeout(struct rendez *rv, int (*cond)(void*), void *arg,
                          uint64_t usec)
{
	int8_t irq_state = 0;
	struct alarm_waiter awaiter;
	struct cv_lookup_elm cle;
	struct timer_chain *pcpui_tchain = &per_cpu_info[core_id()].tchain;

	if (!usec)
		return;
	/* Doing this cond check early, but then unlocking again.  Mostly just to
	 * avoid weird issues with the CV lock and the alarm tchain lock. */
	cv_lock_irqsave(&rv->cv, &irq_state);
	if (cond(arg)) {
		cv_unlock_irqsave(&rv->cv, &irq_state);
		return;
	}
	cv_unlock_irqsave(&rv->cv, &irq_state);
	/* The handler will call rendez_wake, but won't mess with the condition
	 * state.  It's enough to break us out of cv_wait() to see .on_tchain. */
	init_awaiter(&awaiter, rendez_alarm_handler);
	awaiter.data = rv;
	set_awaiter_rel(&awaiter, usec);
	/* Set our alarm on this cpu's tchain.  Note that when we sleep in cv_wait,
	 * we could be migrated, and later on we could be unsetting the alarm
	 * remotely. */
	set_alarm(pcpui_tchain, &awaiter);
	cv_lock_irqsave(&rv->cv, &irq_state);
	__reg_abortable_cv(&cle, &rv->cv);
	/* We could wake early for a few reasons.  Legit wakeups after a changed
	 * condition (and we should exit), other alarms with different timeouts (and
	 * we should go back to sleep), etc.  Note it is possible for our alarm to
	 * fire immediately upon setting it: before we even cv_lock. */
	while (!cond(arg) && awaiter.on_tchain) {
		if (should_abort(&cle)) {
			cv_unlock_irqsave(&rv->cv, &irq_state);
			unset_alarm(pcpui_tchain, &awaiter);
			dereg_abortable_cv(&cle);
			error(EINTR, "syscall aborted");
		}
		cv_wait(&rv->cv);
		cpu_relax();
	}
	cv_unlock_irqsave(&rv->cv, &irq_state);
	dereg_abortable_cv(&cle);
	/* Turn off our alarm.  If it already fired, this is a no-op.  Note this
	 * could be cross-core. */
	unset_alarm(pcpui_tchain, &awaiter);
}

int
cv_wait_sig(kcondvar_t *cvp, kmutex_t *mp)
{
	kthread_t *t = curthread;
	proc_t *p = ttoproc(t);
	klwp_t *lwp = ttolwp(t);
	int rval = 1;
	int signalled = 0;

	if (panicstr)
		return (rval);

	/*
	 * The check for t_intr is to catch an interrupt thread
	 * that has not yet unpinned the thread underneath.
	 */
	if (lwp == NULL || t->t_intr) {
		cv_wait(cvp, mp);
		return (rval);
	}

	ASSERT(curthread->t_schedflag & TS_DONT_SWAP);
	lwp->lwp_asleep = 1;
	lwp->lwp_sysabort = 0;
	thread_lock(t);
	cv_block_sig(t, (condvar_impl_t *)cvp);
	thread_unlock_nopreempt(t);
	mutex_exit(mp);
	if (ISSIG(t, JUSTLOOKING) || MUSTRETURN(p, t))
		setrun(t);
	/* ASSERT(no locks are held) */
	swtch();
	signalled = (t->t_schedflag & TS_SIGNALLED);
	t->t_flag &= ~T_WAKEABLE;
	mutex_enter(mp);
	if (ISSIG_PENDING(t, lwp, p)) {
		mutex_exit(mp);
		if (issig(FORREAL))
			rval = 0;
		mutex_enter(mp);
	}
	if (lwp->lwp_sysabort || MUSTRETURN(p, t))
		rval = 0;
	lwp->lwp_asleep = 0;
	lwp->lwp_sysabort = 0;
	if (rval == 0 && signalled)	/* avoid consuming the cv_signal() */
		cv_signal(cvp);
	return (rval);
}

void
zfs_delete_thread(void *arg)
{
	zfsvfs_t	*zfsvfs = arg;
	zfs_delete_t 	*zd = &zfsvfs->z_delete_head;
	znode_t		*zp;
	callb_cpr_t	cprinfo;
	int		drained;

	CALLB_CPR_INIT(&cprinfo, &zd->z_mutex, callb_generic_cpr, "zfs_delete");

	mutex_enter(&zd->z_mutex);

	if (!zd->z_drained && !zd->z_draining) {
		zd->z_draining = B_TRUE;
		mutex_exit(&zd->z_mutex);
		drained = zfs_drain_dq(zfsvfs);
		mutex_enter(&zd->z_mutex);
		zd->z_draining = B_FALSE;
		zd->z_drained = drained;
		cv_broadcast(&zd->z_quiesce_cv);
	}

	while (zd->z_thread_count <= zd->z_thread_target) {
		zp = list_head(&zd->z_znodes);
		if (zp == NULL) {
			ASSERT(zd->z_znode_count == 0);
			CALLB_CPR_SAFE_BEGIN(&cprinfo);
			cv_wait(&zd->z_cv, &zd->z_mutex);
			CALLB_CPR_SAFE_END(&cprinfo, &zd->z_mutex);
			continue;
		}
		ASSERT(zd->z_znode_count != 0);
		list_remove(&zd->z_znodes, zp);
		if (--zd->z_znode_count == 0)
			cv_broadcast(&zd->z_quiesce_cv);
		mutex_exit(&zd->z_mutex);
		zfs_rmnode(zp);
		(void) zfs_delete_thread_target(zfsvfs, -1);
		mutex_enter(&zd->z_mutex);
	}

	ASSERT(zd->z_thread_count != 0);
	if (--zd->z_thread_count == 0)
		cv_broadcast(&zd->z_cv);

	CALLB_CPR_EXIT(&cprinfo);	/* NB: drops z_mutex */
	thread_exit();
}

/*
 * xpvtap_user_thread_stop()
 */
static void
xpvtap_user_thread_stop(xpvtap_state_t *state)
{
	/* wake thread so it can exit */
	mutex_enter(&state->bt_thread.ut_mutex);
	state->bt_thread.ut_wake = B_TRUE;
	state->bt_thread.ut_exit = B_TRUE;
	cv_signal(&state->bt_thread.ut_wake_cv);
	if (!state->bt_thread.ut_exit_done) {
		cv_wait(&state->bt_thread.ut_exit_done_cv,
		    &state->bt_thread.ut_mutex);
	}
	mutex_exit(&state->bt_thread.ut_mutex);
	ASSERT(state->bt_thread.ut_exit_done);
}

static void
filemon_lock_read(void)
{
	mtx_lock(&access_mtx);

	while (access_owner != NULL || access_requester != NULL)
		cv_wait(&access_cv, &access_mtx);

	n_readers++;

	/* Wake up threads waiting. */
	cv_broadcast(&access_cv);

	mtx_unlock(&access_mtx);
}

static int do_test(struct taskq *tq, char *desc)
{
	mutex_lock(&tq_mutex);
	tq_done = false;
	mutex_unlock(&tq_mutex);

	if (taskq_dispatch(tq, tq_test_func, desc, 0) == 0)
		return 1;

	mutex_lock(&tq_mutex);
	while (!tq_done)
		cv_wait(&tq_wait, &tq_mutex);
	mutex_unlock(&tq_mutex);
	return 0;
}

void
e_ddi_enter_instance()
{
	mutex_enter(&e_ddi_inst_state.ins_serial);
	if (e_ddi_inst_state.ins_thread == curthread)
		e_ddi_inst_state.ins_busy++;
	else {
		while (e_ddi_inst_state.ins_busy)
			cv_wait(&e_ddi_inst_state.ins_serial_cv,
			    &e_ddi_inst_state.ins_serial);
		e_ddi_inst_state.ins_thread = curthread;
		e_ddi_inst_state.ins_busy = 1;
	}
	mutex_exit(&e_ddi_inst_state.ins_serial);
}