qemu: Finish device removal in the original thread

If QEMU supports DEVICE_DELETED event, we always call
qemuDomainRemoveDevice from the event handler. However, we will need to
push this call away from the main event loop and begin a job for it (see
the following commit), we need to make sure the device is fully removed
by the original thread (and within its existing job) in case the
DEVICE_DELETED event arrives before qemuDomainWaitForDeviceRemoval times
out.

Without this patch, device removals would be guaranteed to never finish
before the timeout because the could would be blocked by the original
job being still active.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_hotplug.c

@@ -2780,8 +2780,9 @@ qemuDomainResetDeviceRemoval(virDomainObjPtr vm)
 /* Returns:
  *  -1 on error
  *   0 when DEVICE_DELETED event is unsupported
- *   1 when device removal finished
- *   2 device removal did not finish in QEMU_REMOVAL_WAIT_TIME
+ *   1 when DEVICE_DELETED arrived before the timeout and the caller is
+ *     responsible for finishing the removal
+ *   2 device removal did not finish in qemuDomainRemoveDeviceWaitTime
  */
 static int
 qemuDomainWaitForDeviceRemoval(virDomainObjPtr vm)
@@ -2812,7 +2813,13 @@ qemuDomainWaitForDeviceRemoval(virDomainObjPtr vm)
     return 1;
 }
 
-void
+/* Returns:
+ *  true    there was a thread waiting for devAlias to be removed and this
+ *          thread will take care of finishing the removal
+ *  false   the thread that started the removal is already gone and delegate
+ *          finishing the removal to a new thread
+ */
+bool
 qemuDomainSignalDeviceRemoval(virDomainObjPtr vm,
                               const char *devAlias)
 {
@@ -2821,7 +2828,9 @@ qemuDomainSignalDeviceRemoval(virDomainObjPtr vm,
     if (STREQ_NULLABLE(priv->unpluggingDevice, devAlias)) {
         qemuDomainResetDeviceRemoval(vm);
         virCondSignal(&priv->unplugFinished);
+        return true;
     }
+    return false;
 }
 
 
@@ -2833,6 +2842,7 @@ qemuDomainDetachVirtioDiskDevice(virQEMUDriverPtr driver,
     int ret = -1;
     qemuDomainObjPrivatePtr priv = vm->privateData;
     char *drivestr = NULL;
+    int rc;
 
     if (qemuIsMultiFunctionDevice(vm->def, &detach->info)) {
         virReportError(VIR_ERR_OPERATION_FAILED,
@@ -2889,7 +2899,8 @@ qemuDomainDetachVirtioDiskDevice(virQEMUDriverPtr driver,
 
     qemuDomainObjExitMonitor(driver, vm);
 
-    if (!qemuDomainWaitForDeviceRemoval(vm))
+    rc = qemuDomainWaitForDeviceRemoval(vm);
+    if (rc == 0 || rc == 1)
         qemuDomainRemoveDiskDevice(driver, vm, detach);
     ret = 0;
 
@@ -2907,6 +2918,7 @@ qemuDomainDetachDiskDevice(virQEMUDriverPtr driver,
     int ret = -1;
     qemuDomainObjPrivatePtr priv = vm->privateData;
     char *drivestr = NULL;
+    int rc;
 
     if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
         virReportError(VIR_ERR_OPERATION_FAILED,
@@ -2943,7 +2955,8 @@ qemuDomainDetachDiskDevice(virQEMUDriverPtr driver,
 
     qemuDomainObjExitMonitor(driver, vm);
 
-    if (!qemuDomainWaitForDeviceRemoval(vm))
+    rc = qemuDomainWaitForDeviceRemoval(vm);
+    if (rc == 0 || rc == 1)
         qemuDomainRemoveDiskDevice(driver, vm, detach);
     ret = 0;
 
@@ -3063,6 +3076,7 @@ int qemuDomainDetachControllerDevice(virQEMUDriverPtr driver,
     int idx, ret = -1;
     virDomainControllerDefPtr detach = NULL;
     qemuDomainObjPrivatePtr priv = vm->privateData;
+    int rc;
 
     if ((idx = virDomainControllerFind(vm->def,
                                        dev->data.controller->type,
@@ -3128,7 +3142,8 @@ int qemuDomainDetachControllerDevice(virQEMUDriverPtr driver,
     }
     qemuDomainObjExitMonitor(driver, vm);
 
-    if (!qemuDomainWaitForDeviceRemoval(vm))
+    rc = qemuDomainWaitForDeviceRemoval(vm);
+    if (rc == 0 || rc == 1)
         qemuDomainRemoveControllerDevice(driver, vm, detach);
 
     ret = 0;
@@ -3280,10 +3295,13 @@ qemuDomainDetachThisHostDevice(virQEMUDriverPtr driver,
         return -1;
     }
 
-    if (ret < 0)
+    if (ret < 0) {
         virDomainAuditHostdev(vm, detach, "detach", false);
-    else if (!qemuDomainWaitForDeviceRemoval(vm))
-        qemuDomainRemoveHostDevice(driver, vm, detach);
+    } else {
+        int rc = qemuDomainWaitForDeviceRemoval(vm);
+        if (rc == 0 || rc == 1)
+            qemuDomainRemoveHostDevice(driver, vm, detach);
+    }
 
     qemuDomainResetDeviceRemoval(vm);
 
@@ -3361,6 +3379,7 @@ qemuDomainDetachNetDevice(virQEMUDriverPtr driver,
     qemuDomainObjPrivatePtr priv = vm->privateData;
     int vlan;
     char *hostnet_name = NULL;
+    int rc;
 
     if ((detachidx = virDomainNetFindIdx(vm->def, dev->data.net)) < 0)
         goto cleanup;
@@ -3440,7 +3459,8 @@ qemuDomainDetachNetDevice(virQEMUDriverPtr driver,
     }
     qemuDomainObjExitMonitor(driver, vm);
 
-    if (!qemuDomainWaitForDeviceRemoval(vm))
+    rc = qemuDomainWaitForDeviceRemoval(vm);
+    if (rc == 0 || rc == 1)
         qemuDomainRemoveNetDevice(driver, vm, detach);
 
     ret = 0;
@@ -3578,6 +3598,7 @@ int qemuDomainDetachChrDevice(virQEMUDriverPtr driver,
     virDomainChrDefPtr tmpChr;
     char *charAlias = NULL;
     char *devstr = NULL;
+    int rc;
 
     if (!(tmpChr = virDomainChrFind(vmdef, chr))) {
         virReportError(VIR_ERR_OPERATION_INVALID, "%s",
@@ -3605,7 +3626,8 @@ int qemuDomainDetachChrDevice(virQEMUDriverPtr driver,
     }
     qemuDomainObjExitMonitor(driver, vm);
 
-    if (!qemuDomainWaitForDeviceRemoval(vm))
+    rc = qemuDomainWaitForDeviceRemoval(vm);
+    if (rc == 0 || rc == 1)
         qemuDomainRemoveChrDevice(driver, vm, tmpChr);
     ret = 0;
 

src/qemu/qemu_hotplug.h

@@ -106,7 +106,7 @@ void qemuDomainRemoveDevice(virQEMUDriverPtr driver,
                             virDomainObjPtr vm,
                             virDomainDeviceDefPtr dev);
 
-void qemuDomainSignalDeviceRemoval(virDomainObjPtr vm,
+bool qemuDomainSignalDeviceRemoval(virDomainObjPtr vm,
                                    const char *devAlias);
 
 #endif /* __QEMU_HOTPLUG_H__ */

src/qemu/qemu_process.c

@@ -1381,7 +1381,8 @@ qemuProcessHandleDeviceDeleted(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
     VIR_DEBUG("Device %s removed from domain %p %s",
               devAlias, vm, vm->def->name);
 
-    qemuDomainSignalDeviceRemoval(vm, devAlias);
+    if (qemuDomainSignalDeviceRemoval(vm, devAlias))
+        goto cleanup;
 
     if (virDomainDefFindDevice(vm->def, devAlias, &dev, true) < 0)
         goto cleanup;