From c8b4fabc37588d4ad6b341649f93b8e31d354876 Mon Sep 17 00:00:00 2001
From: Peng Tao <bergwolf@gmail.com>
Date: Tue, 31 Jul 2018 11:39:19 +0800
Subject: [PATCH 1/2] qemu: clear qmp state before wait for qemu process

So that if there is any remaining state, we do not let it interfere
with the new one. This should fix the occasional vm factory hang.

Fixes: #535

Signed-off-by: Peng Tao <bergwolf@gmail.com>
---
 virtcontainers/qemu.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/virtcontainers/qemu.go b/virtcontainers/qemu.go
index 1d84fa88d7..8002110fd4 100644
--- a/virtcontainers/qemu.go
+++ b/virtcontainers/qemu.go
@@ -517,6 +517,8 @@ func (q *qemu) waitSandbox(timeout int) error {
 	var ver *govmmQemu.QMPVersion
 	var err error
 
+	// clear any possible old state before trying to connect again.
+	q.qmpShutdown()
 	timeStart := time.Now()
 	for {
 		disconnectCh := make(chan struct{})

From 44a3a441aa92f1596389288c8db4daea3011e419 Mon Sep 17 00:00:00 2001
From: Peng Tao <bergwolf@gmail.com>
Date: Tue, 31 Jul 2018 18:18:26 +0800
Subject: [PATCH 2/2] qemu: wait on disconnected channel in qmp shutdown

That is how govmm ensures us that the qmp channel has been cleaned
up entirely.

Signed-off-by: Peng Tao <bergwolf@gmail.com>
---
 virtcontainers/qemu.go      | 16 ++++++++++++----
 virtcontainers/qemu_test.go | 15 +++++++++++++++
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/virtcontainers/qemu.go b/virtcontainers/qemu.go
index 8002110fd4..ca3d63ee84 100644
--- a/virtcontainers/qemu.go
+++ b/virtcontainers/qemu.go
@@ -25,9 +25,10 @@ import (
 )
 
 type qmpChannel struct {
-	ctx  context.Context
-	path string
-	qmp  *govmmQemu.QMP
+	ctx     context.Context
+	path    string
+	qmp     *govmmQemu.QMP
+	disconn chan struct{}
 }
 
 // CPUDevice represents a CPU device which was hot-added in a running VM
@@ -514,6 +515,7 @@ func (q *qemu) waitSandbox(timeout int) error {
 	cfg := govmmQemu.QMPConfig{Logger: newQMPLogger()}
 
 	var qmp *govmmQemu.QMP
+	var disconnectCh chan struct{}
 	var ver *govmmQemu.QMPVersion
 	var err error
 
@@ -521,7 +523,7 @@ func (q *qemu) waitSandbox(timeout int) error {
 	q.qmpShutdown()
 	timeStart := time.Now()
 	for {
-		disconnectCh := make(chan struct{})
+		disconnectCh = make(chan struct{})
 		qmp, ver, err = govmmQemu.QMPStart(q.qmpMonitorCh.ctx, q.qmpMonitorCh.path, cfg, disconnectCh)
 		if err == nil {
 			break
@@ -534,6 +536,7 @@ func (q *qemu) waitSandbox(timeout int) error {
 		time.Sleep(time.Duration(50) * time.Millisecond)
 	}
 	q.qmpMonitorCh.qmp = qmp
+	q.qmpMonitorCh.disconn = disconnectCh
 	defer q.qmpShutdown()
 
 	qemuMajorVersion = ver.Major
@@ -619,6 +622,7 @@ func (q *qemu) qmpSetup() error {
 		return err
 	}
 	q.qmpMonitorCh.qmp = qmp
+	q.qmpMonitorCh.disconn = disconnectCh
 
 	return nil
 }
@@ -626,7 +630,11 @@ func (q *qemu) qmpSetup() error {
 func (q *qemu) qmpShutdown() {
 	if q.qmpMonitorCh.qmp != nil {
 		q.qmpMonitorCh.qmp.Shutdown()
+		// wait on disconnected channel to be sure that the qmp channel has
+		// been closed cleanly.
+		<-q.qmpMonitorCh.disconn
 		q.qmpMonitorCh.qmp = nil
+		q.qmpMonitorCh.disconn = nil
 	}
 }
 
diff --git a/virtcontainers/qemu_test.go b/virtcontainers/qemu_test.go
index 55b443ea75..6b069f12ad 100644
--- a/virtcontainers/qemu_test.go
+++ b/virtcontainers/qemu_test.go
@@ -345,3 +345,18 @@ func TestHotplugUnsupportedDeviceType(t *testing.T) {
 	_, err = q.hotplugRemoveDevice(&memoryDevice{0, 128}, fsDev)
 	assert.Error(err)
 }
+
+func TestQMPSetupShutdown(t *testing.T) {
+	assert := assert.New(t)
+
+	qemuConfig := newQemuConfig()
+	q := &qemu{
+		config: qemuConfig,
+	}
+
+	q.qmpShutdown()
+
+	q.qmpMonitorCh.qmp = &govmmQemu.QMP{}
+	err := q.qmpSetup()
+	assert.Nil(err)
+}