[libvirt] [RFC PATCH 06/10] qemu: implement state driver shutdown function

[John Ferlan]

From: Nikolay Shirokovskiy <nshirokovskiy at virtuozzo.com>

Shutdown function should help API calls to finish when
event loop is not running anymore. For this reason let's
close agent and qemu monitors. These function will unblock
API calls wating for response from qemu process or qemu agent.

Closing agent monitor and setting priv->agent to NULL when
waiting for response is normal usecase (handling EOF from
agent is handled the same way for example).

However we can not do the same for qemu monitor. This monitor is normally
closed and unrefed during qemuProcessStop under destroy job so other threads
do not deal with priv->mon. But if we take extra reference to monitor
we are good. This can lead to double close but this function looks like to
be idempotent.

Signed-off-by: John Ferlan <jferlan at redhat.com>
---
 src/qemu/qemu_driver.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index a203c9297..1de236cb5 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -1093,6 +1093,44 @@ qemuStateStop(void)
     return ret;
 }
 
+
+static int
+qemuDomainDisconnect(virDomainObjPtr vm, void *opaque ATTRIBUTE_UNUSED)
+{
+
+    qemuDomainObjPrivatePtr priv;
+
+    virObjectLock(vm);
+    priv = vm->privateData;
+
+    if (priv->mon) {
+        /* Take extra reference to monitor so it won't be disposed
+         * by qemuMonitorClose last unref. */
+        virObjectRef(priv->mon);
+        qemuMonitorClose(priv->mon);
+    }
+
+    if (priv->agent) {
+        /* Other threads are ready for priv->agent to became NULL meanwhile */
+        qemuAgentClose(priv->agent);
+        priv->agent = NULL;
+    }
+
+    virObjectUnlock(vm);
+    return 0;
+}
+
+
+static void
+qemuStateShutdown(void)
+{
+    if (!qemu_driver)
+        return;
+
+    virDomainObjListForEach(qemu_driver->domains, qemuDomainDisconnect, NULL);
+}
+
+
 /**
  * qemuStateCleanup:
  *
@@ -21357,6 +21395,7 @@ static virStateDriver qemuStateDriver = {
     .stateCleanup = qemuStateCleanup,
     .stateReload = qemuStateReload,
     .stateStop = qemuStateStop,
+    .stateShutdown = qemuStateShutdown,
 };
 
 int qemuRegister(void)
-- 
2.13.6