File libvirt-qemu-Process-DEVICE_DELETED-event-in-a-separate-thread.patch of Package libvirt

From 3a8cdc2c7ead128083ec15ccd5655af4fb83df15 Mon Sep 17 00:00:00 2001
Message-Id: <3a8cdc2c7ead128083ec15ccd5655af4fb83df15@dist-git>
From: Jiri Denemark <jdenemar@redhat.com>
Date: Mon, 26 May 2014 17:02:05 +0200
Subject: [PATCH] qemu: Process DEVICE_DELETED event in a separate thread

Currently, we don not acquire any job when removing a device after
DEVICE_DELETED event was received from QEMU. This means that if there is
another API running at the time DEVICE_DELETED is delivered and the API
acquired a job, we may happily change the definition of the domain the
API is working with whenever it unlocks the domain object (e.g., to talk
with its monitor). That said, we have to acquire a job before finishing
device removal to make things safe. However, doing so in the main event
loop would cause a deadlock so we need to move most of the event handler
into a separate thread.

Another good reason for both acquiring a job and handling the event in a
separate thread is that we currently remove a device backend immediately
after removing its frontend while we should only remove the backend once
we already received DEVICE_DELETED event. That is, we will have to talk
to QEMU monitor from the event handler.

https://bugzilla.redhat.com/show_bug.cgi?id=807023

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
(cherry picked from commit 47f424c2d929a820f9bde6819013457e53dbee56)
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

Conflicts:
	src/qemu/qemu_process.c - downstream changes made by earlier
	    patches in this series

Downstream changes:
    - no VIR_STRDUP
    - old spelling of virQEMUDriverPtr
    - virQEMUDriverConfigPtr was not separated from struct qemu_driver
---
 src/qemu/qemu_domain.h  |  2 ++
 src/qemu/qemu_driver.c  | 46 ++++++++++++++++++++++++++++++++++++++++++++--
 src/qemu/qemu_process.c | 27 +++++++++++++++++++++------
 3 files changed, 67 insertions(+), 8 deletions(-)

diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index b41fb2f..90e26ff 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -170,6 +170,7 @@ struct _qemuDomainObjPrivate {
 typedef enum {
     QEMU_PROCESS_EVENT_WATCHDOG = 0,
     QEMU_PROCESS_EVENT_GUESTPANIC,
+    QEMU_PROCESS_EVENT_DEVICE_DELETED,
 
     QEMU_PROCESS_EVENT_LAST
 } qemuProcessEventType;
@@ -178,6 +179,7 @@ struct qemuProcessEvent {
     virDomainObjPtr vm;
     qemuProcessEventType eventType;
     int action;
+    void *data;
 };
 
 const char *qemuDomainAsyncJobPhaseToString(enum qemuDomainAsyncJob job,
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 42081f1..e929600 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -3918,6 +3918,45 @@ cleanup:
     ;
 }
 
+
+static void
+processDeviceDeletedEvent(struct qemud_driver *driver,
+                          virDomainObjPtr vm,
+                          char *devAlias)
+{
+    virDomainDeviceDef dev;
+
+    VIR_DEBUG("Removing device %s from domain %p %s",
+              devAlias, vm, vm->def->name);
+
+    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
+        goto cleanup;
+
+    if (!virDomainObjIsActive(vm)) {
+        VIR_DEBUG("Domain is not running");
+        goto endjob;
+    }
+
+    if (virDomainDefFindDevice(vm->def, devAlias, &dev, true) < 0)
+        goto endjob;
+
+    qemuDomainRemoveDevice(driver, vm, &dev);
+
+    if (virDomainSaveStatus(driver->caps, driver->stateDir, vm) < 0)
+        VIR_WARN("unable to save domain status after removing device %s",
+                 devAlias);
+
+ endjob:
+    /* We had an extra reference to vm before starting a new job so ending the
+     * job is guaranteed not to remove the last reference.
+     */
+    ignore_value(qemuDomainObjEndJob(driver, vm));
+
+ cleanup:
+    VIR_FREE(devAlias);
+}
+
+
 static void qemuProcessEventHandler(void *data, void *opaque)
 {
     struct qemuProcessEvent *processEvent = data;
@@ -3936,8 +3975,11 @@ static void qemuProcessEventHandler(void *data, void *opaque)
     case QEMU_PROCESS_EVENT_GUESTPANIC:
         processGuestPanicEvent(driver, vm, processEvent->action);
         break;
-    default:
-       break;
+    case QEMU_PROCESS_EVENT_DEVICE_DELETED:
+        processDeviceDeletedEvent(driver, vm, processEvent->data);
+        break;
+    case QEMU_PROCESS_EVENT_LAST:
+        break;
     }
 
     virDomainObjUnlock(vm);
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index e25600c..039340f 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -1364,7 +1364,8 @@ qemuProcessHandleDeviceDeleted(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
                                const char *devAlias)
 {
     struct qemud_driver *driver = qemu_driver;
-    virDomainDeviceDef dev;
+    struct qemuProcessEvent *processEvent = NULL;
+    char *data;
 
     qemuDriverLock(driver);
     virDomainObjLock(vm);
@@ -1375,18 +1376,32 @@ qemuProcessHandleDeviceDeleted(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
     if (qemuDomainSignalDeviceRemoval(vm, devAlias))
         goto cleanup;
 
-    if (virDomainDefFindDevice(vm->def, devAlias, &dev, true) < 0)
-        goto cleanup;
+    if (VIR_ALLOC(processEvent) < 0)
+        goto error;
 
-    qemuDomainRemoveDevice(driver, vm, &dev);
+    processEvent->eventType = QEMU_PROCESS_EVENT_DEVICE_DELETED;
+    if (!(data = strdup(devAlias))) {
+        virReportOOMError();
+        goto error;
+    }
+    processEvent->data = data;
+    processEvent->vm = vm;
 
-    if (virDomainSaveStatus(driver->caps, driver->stateDir, vm) < 0)
-        VIR_WARN("unable to save domain status with balloon change");
+    virObjectRef(vm);
+    if (virThreadPoolSendJob(driver->workerPool, 0, processEvent) < 0) {
+        ignore_value(virObjectUnref(vm));
+        goto error;
+    }
 
 cleanup:
     virDomainObjUnlock(vm);
     qemuDriverUnlock(driver);
     return 0;
+error:
+    if (processEvent)
+        VIR_FREE(processEvent->data);
+    VIR_FREE(processEvent);
+    goto cleanup;
 }
 
 
-- 
2.0.0