C++ rmb函数代码示例

/**
 * amdgpu_ih_process - interrupt handler
 *
 * @adev: amdgpu_device pointer
 *
 * Interrupt hander (VI), walk the IH ring.
 * Returns irq process return code.
 */
int amdgpu_ih_process(struct amdgpu_device *adev)
{
	struct amdgpu_iv_entry entry;
	u32 wptr;

	if (!adev->irq.ih.enabled || adev->shutdown)
		return IRQ_NONE;

	wptr = amdgpu_ih_get_wptr(adev);

restart_ih:
	/* is somebody else already processing irqs? */
	if (atomic_xchg(&adev->irq.ih.lock, 1))
		return IRQ_NONE;

	DRM_DEBUG("%s: rptr %d, wptr %d\n", __func__, adev->irq.ih.rptr, wptr);

	/* Order reading of wptr vs. reading of IH ring data */
	rmb();

	while (adev->irq.ih.rptr != wptr) {
		u32 ring_index = adev->irq.ih.rptr >> 2;

		/* Before dispatching irq to IP blocks, send it to amdkfd */
		amdgpu_amdkfd_interrupt(adev,
				(const void *) &adev->irq.ih.ring[ring_index]);

		entry.iv_entry = (const uint32_t *)
			&adev->irq.ih.ring[ring_index];
		amdgpu_ih_decode_iv(adev, &entry);
		adev->irq.ih.rptr &= adev->irq.ih.ptr_mask;

		amdgpu_irq_dispatch(adev, &entry);
	}
	amdgpu_ih_set_rptr(adev);
	atomic_set(&adev->irq.ih.lock, 0);

	/* make sure wptr hasn't changed while processing */
	wptr = amdgpu_ih_get_wptr(adev);
	if (wptr != adev->irq.ih.rptr)
		goto restart_ih;

	return IRQ_HANDLED;
}

static
int i2400mu_suspend(struct usb_interface *iface, pm_message_t pm_msg)
{
	int result = 0;
	struct device *dev = &iface->dev;
	struct i2400mu *i2400mu = usb_get_intfdata(iface);
	unsigned is_autosuspend = 0;
	struct i2400m *i2400m = &i2400mu->i2400m;

#ifdef CONFIG_PM
	if (PMSG_IS_AUTO(pm_msg))
		is_autosuspend = 1;
#endif

	d_fnstart(3, dev, "(iface %p pm_msg %u)\n", iface, pm_msg.event);
	rmb();		
	if (i2400m->updown == 0)
		goto no_firmware;
	if (i2400m->state == I2400M_SS_DATA_PATH_CONNECTED && is_autosuspend) {
		result = -EBADF;
		d_printf(1, dev, "fw up, link up, not-idle, autosuspend: "
			 "not entering powersave\n");
		goto error_not_now;
	}
	d_printf(1, dev, "fw up: entering powersave\n");
	atomic_dec(&i2400mu->do_autopm);
	result = i2400m_cmd_enter_powersave(i2400m);
	atomic_inc(&i2400mu->do_autopm);
	if (result < 0 && !is_autosuspend) {
		
		dev_err(dev, "failed to suspend, will reset on resume\n");
		result = 0;
	}
	if (result < 0)
		goto error_enter_powersave;
	i2400mu_notification_release(i2400mu);
	d_printf(1, dev, "powersave requested\n");
error_enter_powersave:
error_not_now:
no_firmware:
	d_fnend(3, dev, "(iface %p pm_msg %u) = %d\n",
		iface, pm_msg.event, result);
	return result;
}

void _iwl_read_targ_mem_words(struct iwl_bus *bus, u32 addr,
                              void *buf, int words)
{
    unsigned long flags;
    int offs;
    u32 *vals = buf;

    spin_lock_irqsave(&bus->reg_lock, flags);
    iwl_grab_nic_access(bus);

    iwl_write32(bus, HBUS_TARG_MEM_RADDR, addr);
    rmb();

    for (offs = 0; offs < words; offs++)
        vals[offs] = iwl_read32(bus, HBUS_TARG_MEM_RDAT);

    iwl_release_nic_access(bus);
    spin_unlock_irqrestore(&bus->reg_lock, flags);
}

/*
 * Waiting for a read lock or a write lock on a rwlock...
 * This turns out to be the same for read and write locks, since
 * we only know the holder if it is write-locked.
 */
void __rw_yield(arch_rwlock_t *rw)
{
	int lock_value;
	unsigned int holder_cpu, yield_count;

	lock_value = rw->lock;
	if (lock_value >= 0)
		return;		/* no write lock at present */
	holder_cpu = lock_value & 0xffff;
	BUG_ON(holder_cpu >= NR_CPUS);
	yield_count = be32_to_cpu(lppaca_of(holder_cpu).yield_count);
	if ((yield_count & 1) == 0)
		return;		/* virtual cpu is currently running */
	rmb();
	if (rw->lock != lock_value)
		return;		/* something has changed */
	plpar_hcall_norets(H_CONFER,
		get_hard_smp_processor_id(holder_cpu), yield_count);
}

/*
 * The idle thread. There's no useful work to be
 * done, so just try to conserve power and have a
 * low exit latency (ie sit in a loop waiting for
 * somebody to say that they'd like to reschedule)
 */
void cpu_idle(void)
{
	int cpu = smp_processor_id();

	/*
	 * If we're the non-boot CPU, nothing set the stack canary up
	 * for us.  CPU0 already has it initialized but no harm in
	 * doing it again.  This is a good place for updating it, as
	 * we wont ever return from this function (so the invalid
	 * canaries already on the stack wont ever trigger).
	 */
	boot_init_stack_canary();

	current_thread_info()->status |= TS_POLLING;

	/* endless idle loop with no priority at all */
	while (1) {
		tick_nohz_idle_enter();
		rcu_idle_enter();
		while (!need_resched()) {

			check_pgt_cache();
			rmb();

			if (cpu_is_offline(cpu))
				play_dead();

			local_touch_nmi();
			local_irq_disable();
			/* Don't trace irqs off for idle */
			stop_critical_timings();
			if (cpuidle_idle_call())
				pm_idle();
			start_critical_timings();
		}
		rcu_idle_exit();
		tick_nohz_idle_exit();
		preempt_enable_no_resched();
		schedule();
		preempt_disable();
	}
}

static void xdma_err_tasklet(unsigned long data)
{
	struct xdma_chan *chan = (struct xdma_chan *)data;

	if (chan->err) {
		/* If reset failed, need to hard reset
		 * Channel is no longer functional
		 */
		if (!dma_init(chan))
			chan->err = 0;
		else
			dev_err(chan->dev,
			    "DMA channel reset failed, please reset system\n");
	}

	rmb();
	xilinx_chan_desc_cleanup(chan);

	xilinx_chan_desc_reinit(chan);
}

/*
 * When we write to the ring buffer, check if the host needs to
 * be signaled. Here is the details of this protocol:
 *
 *	1. The host guarantees that while it is draining the
 *	   ring buffer, it will set the interrupt_mask to
 *	   indicate it does not need to be interrupted when
 *	   new data is placed.
 *
 *	2. The host guarantees that it will completely drain
 *	   the ring buffer before exiting the read loop. Further,
 *	   once the ring buffer is empty, it will clear the
 *	   interrupt_mask and re-check to see if new data has
 *	   arrived.
 */
static boolean_t
hv_ring_buffer_needsig_on_write(
	uint32_t			old_write_location,
	hv_vmbus_ring_buffer_info*	rbi)
{
	mb();
	if (rbi->ring_buffer->interrupt_mask)
		return (FALSE);

	/* Read memory barrier */
	rmb();
	/*
	 * This is the only case we need to signal when the
	 * ring transitions from being empty to non-empty.
	 */
	if (old_write_location == rbi->ring_buffer->read_index)
		return (TRUE);

	return (FALSE);
}

static int
netmap_pipe_rxsync(struct netmap_kring *rxkring, int flags)
{
        struct netmap_kring *txkring = rxkring->pipe;
	uint32_t oldhwcur = rxkring->nr_hwcur;

        ND("%s %x <- %s", rxkring->name, flags, txkring->name);
        rxkring->nr_hwcur = rxkring->rhead; /* recover user-relased slots */
        ND(5, "hwcur %d hwtail %d cur %d head %d tail %d", rxkring->nr_hwcur, rxkring->nr_hwtail,
                rxkring->rcur, rxkring->rhead, rxkring->rtail);
        rmb(); /* paired with the first wmb() in txsync */
        nm_rxsync_finalize(rxkring);

	if (oldhwcur != rxkring->nr_hwcur) {
		/* we have released some slots, notify the other end */
		wmb(); /* make sure nr_hwcur is updated before notifying */
		txkring->na->nm_notify(txkring->na, txkring->ring_id, NR_TX, 0);
	}
        return 0;
}

static
int i2400mu_resume(struct usb_interface *iface)
{
	int ret = 0;
	struct device *dev = &iface->dev;
	struct i2400mu *i2400mu = usb_get_intfdata(iface);
	struct i2400m *i2400m = &i2400mu->i2400m;

	d_fnstart(3, dev, "(iface %p)\n", iface);
	rmb();		
	if (i2400m->updown == 0) {
		d_printf(1, dev, "fw was down, no resume neeed\n");
		goto out;
	}
	d_printf(1, dev, "fw was up, resuming\n");
	i2400mu_notification_setup(i2400mu);
out:
	d_fnend(3, dev, "(iface %p) = %d\n", iface, ret);
	return ret;
}

void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
{
	struct vring_virtqueue *vq = to_vvq(_vq);
	u16 last_used;
	unsigned i;
	void *ret;

	rmb();

	last_used = (vq->last_used_idx & (vq->vring.num-1));
	i = vq->vring.used->ring[last_used].id;
	*len = vq->vring.used->ring[last_used].len;

	ret = vq->data[i];
	detach_buf(vq, i);

	vq->last_used_idx++;

	return ret;
}

static void omap_crtc_atomic_flush(struct drm_crtc *crtc,
                                  struct drm_crtc_state *old_crtc_state)
{
	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);

	WARN_ON(omap_crtc->vblank_irq.registered);

	if (dispc_mgr_is_enabled(omap_crtc->channel)) {

		DBG("%s: GO", omap_crtc->name);

		rmb();
		WARN_ON(omap_crtc->pending);
		omap_crtc->pending = true;
		wmb();

		dispc_mgr_go(omap_crtc->channel);
		omap_irq_register(crtc->dev, &omap_crtc->vblank_irq);
	}
}

static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
{
	struct vring_virtqueue *vq = to_vvq(_vq);
	void *ret;
	unsigned int i;

	START_USE(vq);

	if (unlikely(vq->broken)) {
		END_USE(vq);
		return NULL;
	}

	if (!more_used(vq)) {
		pr_debug("No more buffers in queue\n");
		END_USE(vq);
		return NULL;
	}

	/* Only get used array entries after they have been exposed by host. */
	rmb();

	i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
	*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;

	if (unlikely(i >= vq->vring.num)) {
		BAD_RING(vq, "id %u out of range\n", i);
		return NULL;
	}
	if (unlikely(!vq->data[i])) {
		BAD_RING(vq, "id %u is not a head!\n", i);
		return NULL;
	}

	/* detach_buf clears data, so grab it now. */
	ret = vq->data[i];
	detach_buf(vq, i);
	vq->last_used_idx++;
	END_USE(vq);
	return ret;
}

static int htifblk_segment(struct htifblk_device *dev,
	struct request *req)
{
	static struct htifblk_request pkt __aligned(HTIF_ALIGN);
	u64 offset, size, end;
	unsigned long cmd;

	offset = (blk_rq_pos(req) << SECTOR_SIZE_SHIFT);
	size = (blk_rq_cur_sectors(req) << SECTOR_SIZE_SHIFT);

	end = offset + size;
	if (unlikely(end < offset || end > dev->size)) {
		dev_err(&dev->dev->dev, "out-of-bounds access:"
			" offset=%llu size=%llu\n", offset, size);
		return -EINVAL;
	}

	rmb();
	pkt.addr = __pa(req->buffer);
	pkt.offset = offset;
	pkt.size = size;
	pkt.tag = dev->tag;

	switch (rq_data_dir(req)) {
	case READ:
		cmd = HTIF_CMD_READ;
		break;
	case WRITE:
		cmd = HTIF_CMD_WRITE;
		break;
	default:
		return -EINVAL;
	}

	dev->req = req;
	dev->msg_buf.dev = dev->dev->index;
	dev->msg_buf.cmd = cmd;
	dev->msg_buf.data = __pa(&pkt);
	htif_tohost(&dev->msg_buf);
	return 0;
}

static void
rtl8169_tx_interrupt(struct net_device *dev, struct rtl8169_private *tp,
                     void *ioaddr)
{
    unsigned long dirty_tx, tx_left;

    assert(dev != NULL);
    assert(tp != NULL);
    assert(ioaddr != NULL);

    dirty_tx = tp->dirty_tx;
    tx_left = tp->cur_tx - dirty_tx;

    while (tx_left > 0) {
        int entry = dirty_tx % NUM_TX_DESC;
        struct sk_buff *skb = tp->Tx_skbuff[entry];
        u32 status;

        rmb();
        status = le32_to_cpu(tp->TxDescArray[entry].status);
        if (status & OWNbit)
            break;

        /* FIXME: is it really accurate for TxErr ? */
        tp->stats.tx_bytes += skb->len >= ETH_ZLEN ?
                              skb->len : ETH_ZLEN;
        tp->stats.tx_packets++;
        rtl8169_unmap_tx_skb(tp->pci_dev, tp->Tx_skbuff + entry,
                             tp->TxDescArray + entry);
        dev_kfree_skb_irq(skb);
        tp->Tx_skbuff[entry] = NULL;
        dirty_tx++;
        tx_left--;
    }

    if (tp->dirty_tx != dirty_tx) {
        tp->dirty_tx = dirty_tx;
        if (netif_queue_stopped(dev))
            netif_wake_queue(dev);
    }
}

void cpm2_pic_init(struct device_node *node)
{
	int i;

	cpm2_intctl = cpm2_map(im_intctl);

	/* Clear the CPM IRQ controller, in case it has any bits set
	 * from the bootloader
	 */

	/* Mask out everything */

	out_be32(&cpm2_intctl->ic_simrh, 0x00000000);
	out_be32(&cpm2_intctl->ic_simrl, 0x00000000);

	wmb();

	/* Ack everything */
	out_be32(&cpm2_intctl->ic_sipnrh, 0xffffffff);
	out_be32(&cpm2_intctl->ic_sipnrl, 0xffffffff);
	wmb();

	/* Dummy read of the vector */
	i = in_be32(&cpm2_intctl->ic_sivec);
	rmb();

	/* Initialize the default interrupt mapping priorities,
	 * in case the boot rom changed something on us.
	 */
	out_be16(&cpm2_intctl->ic_sicr, 0);
	out_be32(&cpm2_intctl->ic_scprrh, 0x05309770);
	out_be32(&cpm2_intctl->ic_scprrl, 0x05309770);

	/* create a legacy host */
	cpm2_pic_host = irq_alloc_host(node, IRQ_HOST_MAP_LINEAR,
				       64, &cpm2_pic_host_ops, 64);
	if (cpm2_pic_host == NULL) {
		printk(KERN_ERR "CPM2 PIC: failed to allocate irq host!\n");
		return;
	}
}