dpdk的中(zhong)(zhong)(zhong)斷(duan)(duan)是用(yong)戶態(tai)的中(zhong)(zhong)(zhong)斷(duan)(duan)，實(shi)現方式是通(tong)過vfio或uio模塊將內核的中(zhong)(zhong)(zhong)斷(duan)(duan)傳遞到用(yong)戶態(tai)，并且(qie)dpdk實(shi)現的中(zhong)(zhong)(zhong)斷(duan)(duan)機制(zhi)屬(shu)于(yu)控(kong)制(zhi)中(zhong)(zhong)(zhong)斷(duan)(duan)，用(yong)來實(shi)現一些(xie)(xie)控(kong)制(zhi)操(cao)作，例如uio中(zhong)(zhong)(zhong)斷(duan)(duan)用(yong)來設置一些(xie)(xie)網(wang)卡(ka)的狀態(tai)之類(lei)。網(wang)卡(ka)收發包過程，還是使用(yong)輪詢的方式從網(wang)卡(ka)接收報(bao)文。

中斷初始化

中斷初始(shi)化主(zhu)要在(zai)rte_eal_intr_init中完成

首先初始(shi)化intr_sources鏈(lian)表(biao)。所有設備的中(zhong)(zhong)斷(duan)(duan)都掛(gua)在這個鏈(lian)表(biao)上，中(zhong)(zhong)斷(duan)(duan)處理線程通過遍歷這個鏈(lian)表(biao)，來執行設備的中(zhong)(zhong)斷(duan)(duan)。

然后(hou)?創(chuang)建intr_pipe管道，用于epoll模(mo)型的(de)消息通知。

再創(chuang)建線(xian)程intr_thread，線(xian)程的(de)(de)執行體是(shi)eal_intr_thread_main()函數，創(chuang)建epoll模(mo)型，遍歷intr_sources鏈表(biao)，監聽已注冊的(de)(de)所有設(she)備的(de)(de)中(zhong)斷事件，并調用對(dui)應設(she)備的(de)(de)中(zhong)斷處(chu)理(li)函數。中(zhong)斷控制(zhi)線(xian)程對(dui)應的(de)(de)例程為(wei)eal_intr_thread_main()，其使(shi)(shi)用了 epoll_create() 創(chuang)建了一個epoll對(dui)象(xiang)，然后使(shi)(shi)用 epoll_ctl() 將intr_pipe的(de)(de)讀(du)端的(de)(de)fd，以及(ji)中(zhong)斷源list中(zhong)的(de)(de)對(dui)應的(de)(de)fd加入到epoll對(dui)象(xiang)的(de)(de)fd interesting list中(zhong)。然后使(shi)(shi)用 epoll_wait() 監聽epoll對(dui)象(xiang)的(de)(de)fd interesting list

static __rte_noreturn void *
eal_intr_thread_main(__rte_unused void *arg)
{
	/* host thread, never break out */
	for (;;) {
		/* build up the epoll fd with all descriptors we are to
		 * wait on then pass it to the handle_interrupts function
		 */
		static struct epoll_event pipe_event = {
			.events = EPOLLIN | EPOLLPRI,
		};
		struct rte_intr_source *src;
		unsigned numfds = 0;

		/* create epoll fd */
		int pfd = epoll_create(1);
		if (pfd < 0)
			rte_panic("Cannot create epoll instance\n");

		pipe_event.data.fd = intr_pipe.readfd;
		/**
		 * add pipe fd into wait list, this pipe is used to
		 * rebuild the wait list.
		 */
		if (epoll_ctl(pfd, EPOLL_CTL_ADD, intr_pipe.readfd,
						&pipe_event) < 0) {
			rte_panic("Error adding fd to %d epoll_ctl, %s\n",
					intr_pipe.readfd, strerror(errno));
		}
		numfds++;

		rte_spinlock_lock(&intr_lock);

		TAILQ_FOREACH(src, &intr_sources, next) {
			struct epoll_event ev;

			if (src->callbacks.tqh_first == NULL)
				continue; /* skip those with no callbacks */
			memset(&ev, 0, sizeof(ev));
			ev.events = EPOLLIN | EPOLLPRI | EPOLLRDHUP | EPOLLHUP;
			ev.data.fd = rte_intr_fd_get(src->intr_handle);

			/**
			 * add all the uio device file descriptor
			 * into wait list.
			 */
			if (epoll_ctl(pfd, EPOLL_CTL_ADD,
					rte_intr_fd_get(src->intr_handle), &ev) < 0) {
				rte_panic("Error adding fd %d epoll_ctl, %s\n",
					rte_intr_fd_get(src->intr_handle),
					strerror(errno));
			}
			else
				numfds++;
		}
		rte_spinlock_unlock(&intr_lock);
		/* serve the interrupt */
		eal_intr_handle_interrupts(pfd, numfds);

		/**
		 * when we return, we need to rebuild the
		 * list of fds to monitor.
		 */
		close(pfd);
	}
}

中斷注冊和注銷

可以通過 rte_intr_callback_register() 注冊一個中斷源以及對應的callback，注冊完成后，中斷控制線程會對其信號進行監聽，內部會將中斷源鏈表中的所有中斷源描述符都加入到epoll實現的紅黑樹中， 當相應中斷源有事件發生時，epoll會調用這些中斷源注冊的回調函數。
還可以通過 rte_intr_callback_unregister() 注銷一個中斷源(yuan)的callback， 此時中斷控制線(xian)程會停止對中斷信號進行監(jian)聽(ting)。相關(guan)示例代(dai)碼(ma)如下

int
mlx4_intr_install(struct mlx4_priv *priv)
{
	const struct rte_eth_intr_conf *const intr_conf =
		&ETH_DEV(priv)->data->dev_conf.intr_conf;
	int rc;

	mlx4_intr_uninstall(priv);
	if (intr_conf->lsc | intr_conf->rmv) {
		if (rte_intr_fd_set(priv->intr_handle, priv->ctx->async_fd))
			return -rte_errno;

		rc = rte_intr_callback_register(priv->intr_handle,
						(void (*)(void *))
						mlx4_interrupt_handler,
						priv);
		if (rc < 0) {
			rte_errno = -rc;
			goto error;
		}
	}
	return 0;
error:
	mlx4_intr_uninstall(priv);
	return -rte_errno;
}

int
mlx4_intr_uninstall(struct mlx4_priv *priv)
{
	int err = rte_errno; /* Make sure rte_errno remains unchanged. */

	if (rte_intr_fd_get(priv->intr_handle) != -1) {
		rte_intr_callback_unregister(priv->intr_handle,
					     (void (*)(void *))
					     mlx4_interrupt_handler,
					     priv);
		if (rte_intr_fd_set(priv->intr_handle, -1))
			return -rte_errno;
	}
	rte_eal_alarm_cancel((void (*)(void *))mlx4_link_status_alarm, priv);
	priv->intr_alarm = 0;
	mlx4_rxq_intr_disable(priv);
	rte_errno = err;
	return 0;
}

相關函數調用圖如下