From 91cc0d5bf845e6144867b9bfcccd9326c980be62 Mon Sep 17 00:00:00 2001
From: Conghui <conghui.chen@intel.com>
Date: Thu, 1 Sep 2022 11:24:30 +0800
Subject: [PATCH] dm: iothread: fix bug in iothread handler

Fix the bug in iothread handler, the event should be read out so that the
next epoll_wait not return directly as the fd can still readable.

Tracked-On: #8181
Signed-off-by: Conghui <conghui.chen@intel.com>
Acked-by: Wang, Yu1 <yu1.wang@intel.com>
---
 devicemodel/core/iothread.c        | 11 +++++++++--
 devicemodel/hw/pci/virtio/virtio.c |  1 +
 devicemodel/include/iothread.h     |  1 +
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/devicemodel/core/iothread.c b/devicemodel/core/iothread.c
index 238ecb375..c572f04e1 100644
--- a/devicemodel/core/iothread.c
+++ b/devicemodel/core/iothread.c
@@ -21,6 +21,7 @@
 
 
 #define MEVENT_MAX 64
+#define MAX_EVENT_NUM 64
 struct iothread_ctx {
 	pthread_t tid;
 	int epfd;
@@ -34,7 +35,8 @@ io_thread(void *arg)
 {
 	struct epoll_event eventlist[MEVENT_MAX];
 	struct iothread_mevent *aevp;
-	int i, n;
+	int i, n, status;
+	char buf[MAX_EVENT_NUM];
 
 	while(ioctx.started) {
 		n = epoll_wait(ioctx.epfd, eventlist, MEVENT_MAX, -1);
@@ -47,8 +49,13 @@ io_thread(void *arg)
 		}
 		for (i = 0; i < n; i++) {
 			aevp = eventlist[i].data.ptr;
-			if (aevp && aevp->run)
+			if (aevp && aevp->run) {
+				/* Mitigate the epoll_wait repeat cycles by reading out the events as more as possile.*/
+				do {
+					status = read(aevp->fd, buf, sizeof(buf));
+				} while (status == MAX_EVENT_NUM);
 				(*aevp->run)(aevp->arg);
+			}
 		}
 	}
 
diff --git a/devicemodel/hw/pci/virtio/virtio.c b/devicemodel/hw/pci/virtio/virtio.c
index 6b5646269..546ec6f31 100644
--- a/devicemodel/hw/pci/virtio/virtio.c
+++ b/devicemodel/hw/pci/virtio/virtio.c
@@ -104,6 +104,7 @@ virtio_set_iothread(struct virtio_base *base,
 			vq->viothrd.idx = idx;
 			vq->viothrd.iomvt.arg = &vq->viothrd;
 			vq->viothrd.iomvt.run = iothread_handler;
+			vq->viothrd.iomvt.fd = vq->viothrd.kick_fd;
 
 			if (!iothread_add(vq->viothrd.kick_fd, &vq->viothrd.iomvt))
 				if (!virtio_register_ioeventfd(base, idx, true))
diff --git a/devicemodel/include/iothread.h b/devicemodel/include/iothread.h
index 6a3cc7167..fb76e9baa 100644
--- a/devicemodel/include/iothread.h
+++ b/devicemodel/include/iothread.h
@@ -10,6 +10,7 @@
 struct iothread_mevent {
 	void (*run)(void *);
 	void *arg;
+	int fd;
 };
 int iothread_add(int fd, struct iothread_mevent *aevt);
 int iothread_del(int fd);